sickle cell disease

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Related to sickle cell disease: sickle cell trait, Sickle cell crisis

Sickle Cell Disease

Definition

Sickle cell disease describes a group of inherited blood disorders characterized by chronic anemia, painful events, and various complications due to associated tissue and organ damage.

Because sickle cell diseases are characterized by the rapid loss of red blood cells as they enter the circulation, they are classified as hemolytic disorders, "hemolytic" referring to the destruction of the cell membrane of red blood cells resulting in the release of hemoglobin.

Description

The most common and best-known type of sickle cell disease is sickle cell anemia, which is also called meniscocytosis, sicklemia, or SS disease. All types of sickle cell disease are caused by a genetic change in hemoglobin, the oxygen-carrying protein inside the red blood cells. The red blood cells of affected individuals contain a predominance of a structural variant of the usual adult hemoglobin. This variant hemoglobin, called sickle hemoglobin, has a tendency to polymerize into rod-like structures that alter the shape of the usually flexible red blood cells. The cells take on a shape that resembles the curved blade of the sickle, an agricultural tool. Sickle cells have a shorter life span than normally shaped red blood cells. This results in chronic anemia characterized by low levels of hemoglobin and decreased numbers of red blood cells. Sickle cells are also less flexible and stickier than normal red blood cells, and can become trapped in small blood vessels preventing blood flow. This compromises the delivery of oxygen, which can result in pain and damage to associated tissues and organs. Sickle cell disease presents with marked variability, even within families.

Carriers of the sickle cell gene are said to have sickle cell trait. Unlike sickle cell disease, sickle cell trait does not cause health problems. In fact, sickle cell trait is protective against malaria, a disease caused by blood-borne parasites transmitted through mosquito bites. According to a widely accepted theory, the genetic mutation associated with the sickle cell trait occurred thousands of years ago. Coincidentally, this mutation increased the likelihood that carriers would survive malaria infection. Survivors then passed the mutation on to their offspring, and the trait became established throughout areas where malaria was common. As populations migrated, so did the sickle cell trait. Today, approximately one in 12 African Americans has sickle cell trait.

Worldwide, it has been estimated that one in every 250,000 babies is born annually with sickle cell disease. Sickle cell disease primarily affects people of African, Mediterranean, Middle Eastern, and Asian Indian ancestry. In the United States, sickle cell disease is most often seen in African Americans, in whom the disease occurs in one out of every 400 births. The disease has been described in individuals from several different ethnic backgrounds and is also seen with increased frequency in Latino Americans—particularly those of Caribbean, Central American, and South American ancestry. Approximately one in every 1000-1400 Latino births are affected.

Causes and symptoms

Humans normally make several types of the oxygen-carrying protein hemoglobin. An individual's stage in development determines whether he or she makes primarily embryonic, fetal, or adult hemoglobins. All types of hemoglobin are made of three components: heme, alpha (or alpha-like) globin, and beta (or beta-like) globin. Sickle hemoglobin is the result of a genetic change in the beta globin component of normal adult hemoglobin. The beta globin gene is located on chromosome 11. The sickle cell form of the beta globin gene results from the substitution of a single DNA nucleotide, or genetic building-block. The change from adenine to thymine at codon (position) 6 of the beta globin gene leads to insertion of the amino acid valine-instead of glutamic acid—at this same position in the beta globin protein. As a result of this change, sickle hemoglobin has unique properties in comparison to the usual type of adult hemoglobin.

Most individuals have two normal copies of the beta globin gene, which make normal beta globin that is incorporated into adult hemoglobin. Individuals who have sickle cell trait (called sickle cell carriers) have one normal beta globin gene and one sickle cell gene. These individuals make both the usual adult hemoglobin and sickle hemoglobin in roughly equal proportions, so they do not experience any health problems as a result of having the trait. Although traces of blood in the urine and difficulty in concentrating the urine can occur, neither represents a significant health problem as a result of sickle cell trait. Of the millions of people with sickle cell trait worldwide, a small handful of individuals have experienced acute symptoms. In these very rare cases, individuals were subject to very severe physical strain.

When both members of a couple are carriers of sickle cell trait, there is a 25% chance in each pregnancy for the baby to inherit two sickle cell genes and have sickle cell anemia, or SS disease. Correspondingly, there is a 50% chance the baby will have sickle cell trait and a 25% chance that the baby will have the usual type of hemoglobin. Other types of sickle cell disease include SC disease, SD disease, and S/beta thalassemia. These conditions are caused by the co-inheritance of the sickle cell gene and another altered beta globin gene. For example, one parent may have sickle cell trait and the other parent may have hemoglobin C trait (another hemoglobin trait that does not cause health problems). For this couple, there would be a 25% chance of SC disease in each pregnancy.

Normal adult hemoglobin transports oxygen from the lungs to tissues throughout the body. Sickle hemoglobin can also transport oxygen. However, once the oxygen is released, sickle hemoglobin tends to polymerize (line-up) into rigid rods that alter the shape of the red blood cell. Sickling of the red blood cell can be triggered by low oxygen, such as occurs in organs with slow blood flow. It can also be triggered by cold temperatures and dehydration.

Sickle cells have a decreased life span in comparison to normal red blood cells. Normal red blood cells survive for approximately 120 days in the bloodstream; sickle cells last only 10-12 days. As a result, the bloodstream is chronically short of red blood cells and hemoglobin, and the affected individual develops anemia.

Sickle cells can create other complications. Due to their shape, they do not fit well through small blood vessels. As an aggravating factor, the outside surfaces of sickle cells may have altered chemical properties that increase the cells' 'stickiness'. These sticky sickle cells are more likely to adhere to the inside surfaces of small blood vessels, as well as to other blood cells. As a result of the sickle cells' shape and stickiness, blockages form in small blood vessels. Such blockages prevent oxygenated blood from reaching areas where it is needed, causing pain as well as organ and tissue damage.

The severity of symptoms cannot be predicted based solely on the genetic inheritance. Some individuals with sickle cell disease develop health- or life-threatening problems in infancy, but others may have only mild symptoms throughout their lives. Individuals may experience varying degrees of health at different stages in the life cycle. For the most part, this clinical variability is unpredictable, and the reasons for the observed variability can not usually be determined. However, certain types of sickle cell disease (i.e. SC disease) tend to result in fewer and less severe symptoms on average than other types of sickle cell disease (i.e. SS disease). Some additional modifying factors are known. For example, elevated levels of fetal hemoglobin in a child or adult can decrease the quantity and severity of some symptoms and complications. Fetal hemoglobin is a normally occurring hemoglobin that usually decreases from over 90% of the total hemoglobin to under 1% during the first year of life. This change is genetically determined, although some individuals may experience elevated levels of fetal hemoglobin due to variation in the genes that control fetal hemoglobin production. Such individuals often experience a reduction in their symptoms and complications due to the ability of fetal hemoglobin to prevent the polymerization of sickle hemoglobin, which leads to sickling of the red blood cell.

There are several symptoms that warrant immediate medical attention, including the following:

signs of infection (fever greater than >101°F or 38.3°C, coughs frequently or breathing trouble, unusual crankiness, feeding difficulties)
signs of severe anemia (pale skin or lips, yellowing of the skin or eyes, very tired, very weak)
signs indicating possible dehydration (vomiting, diarrhea, fewer wet diapers)

other signs (pain or swelling in the abdomen, swollen hands or feet, screams when touched)

These can be signs of various complications that occur in sickle cell disease.

Infections and effects on the spleen

Children with sickle cell disease who are under age three are particularly prone to life-threatening bacterial infections. Streptococcus pneumoniae is the most common offending bacteria, and invasive infection from this organism leads to death in 15% of cases. The spleen, an organ that helps to fight bacterial infections, is particularly vulnerable to the effects of sickling. Sickle cells can impede blood flow through the spleen, causing organ damage, which usually results in loss of spleen function by late childhood. The spleen can also become enlarged due to blockages and/or increased activity of the spleen. Rapid enlargement of the spleen may be a sign of another complication called splenic sequestration, which occurs mostly in young children and can be life-threatening. Widespread sickling in the spleen prevents adequate blood flow from the organ, removing increasing volumes of blood from the circulation and leading to accompanying signs of severe anemia.

Painful events

Painful events, also known as vaso-occlusive events, are a hallmark symptom of sickle cell disease. The frequency and duration of the pain can vary tremendously from person to person and over an individual's life cycle. Painful events are the most common cause of hospitalizations in sickle cell disease. However, only a small portion of individuals with sickle cell disease experience frequent and severe painful events. Most painful events can be managed at home. Pain results when small blood vessel blockages prevent oxygen from reaching tissues. Pain can affect any area of the body, although the extremities, chest, abdomen, and bones are frequently affected sites. There is some evidence that cold temperatures or infection can trigger a painful event, but most events occur for unknown reasons. The hand-foot syndrome, or dactylitis, is a particular type of painful event. Most common in toddlers, dactylitis results in pain and swelling in the hands and feet, sometimes accompanied by a fever.

Anemia

Sickle cells have a high turnover rate leading to a deficit of red blood cells in the bloodstream. Common symptoms of anemia include fatigue, paleness, and a shortness of breath. A particularly severe form of anemia—aplastic anemia—occurs following infection with parvovirus. Parvovirus causes extensive destruction of the bone marrow, bringing production of new red blood cells to a halt. Bone marrow production resumes after seven to 10 days; however, given the short lives of sickle cells, even a brief shut-down in red blood cell production can cause a rapid decline in hemoglobin concentrations.

Delayed growth

The energy demands of the bone marrow for red blood cell production compete with the demands of a growing body. Children with sickle cell anemia may have delayed growth and reach puberty at a later age than normal. By early adulthood, they catch up on growth and attain normal height; however, weight typically remains below average.

Stroke

Children with sickle cell disease have a significantly elevated risk of having a stroke, which can be one of the most concerning complications of sickle cell disease. Approximately 11% of individuals with sickle cell disease will have a recognizable stroke by the age of 20. Magnetic resonance imaging studies have found that 17% of children with sickle cell anemia have evidence of a previous stroke or clinically 'silent' stroke-like events called transient ischemic events. Stroke in sickle cell disease is usually caused by a blockage of a blood vessel, but about one fourth of the time may be caused by a hemorrhage (or rupture) of a blood vessel.

Strokes result in compromised delivery of oxygen to an area of the brain. The consequences of stroke can range from life-threatening, to severe physical or cognitive impairments, to apparent or subtle learning disabilities, to undetectable effects. Common stroke symptoms include weakness or numbness that affects one side of the body, sudden behavioral changes, loss of vision, confusion, loss of speech or the ability to understand spoken words, dizziness, headache, seizures, vomiting, or even coma.

Approximately two-thirds of the children who have a stroke will have at least one more. Transfusions have been shown to decrease the incidence of a second stroke. A recent study showed that children at highest risk to experience a first stroke were 10 times more likely to stroke if untreated when compared to high-risk children treated with chronic blood transfusion therapy. High-risk children were identified using transcranial doppler ultrasound technology to detect individuals with increased blood flow speeds due to constricted intracranial blood vessels.

As of 2003, researchers are investigating various techniques for helping children with memory loss related to strokes caused by sickle cell disease.

Acute chest syndrome

Acute chest syndrome (ACS) is a leading cause of death for individuals with sickle cell disease, and recurrent attacks can lead to permanent lung damage. Therefore rapid diagnosis and treatment is of great importance. ACS can occur at any age and is similar but distinct from pneumonia. Affected persons may experience fever, cough, chest pain, and shortness of breath. ACS seems to have multiple causes including infection, sickling in the small blood vessels of the lungs, fat embolisms to the lungs, or a combination of factors.

Priapism

Males with sickle cell anemia may experience priapism, a condition characterized by a persistent and painful erection of the penis. Due to blood vessel blockage by sickle cells, blood is trapped in the tissue of the penis. Priapism may be short in duration or it may be prolonged. Priapism can be triggered by low oxygen (hypoxemia), alcohol consumption, or sexual intercourse. Since priapism can be extremely painful and result in damage to this tissue causing impotence, rapid treatment is essential.

Kidney disease

The environment in the kidney is particularly prone to damage from sickle cells. Signs of kidney damage can include blood in the urine, incontinence, and enlarged kidneys. Adults with sickle cell disease often experience insufficient functioning of the kidneys, which can progress to kidney failure in a small percentage of adults with sickle cell disease.

Jaundice and gallstones

Jaundice is indicated by a yellow tone in the skin and eyes, and alone it is not a health concern. Jaundice may occur if bilirubin levels increase, which can occur with high levels of red blood cell destruction. Bilirubin is the final product of hemoglobin degradation, and is typically removed from the bloodstream by the liver. Therefore, jaundice can also be a sign of a poorly functioning liver, which may also be evidenced by an enlarged liver. Increased bilirubin also leads to increased chance for gallstones in children with sickle cell disease. Treatment, which may include removal of the gall bladder, may be selected if the gallstones start causing symptoms.

Retinopathy

The blood vessels that supply oxygen to the retina—the tissue at the back of the eye—may be blocked by sickle cells, leading to a condition called retinopathy. This is one of the only complications that is actually more common in SC disease as compared to SS disease. Retinopathy can be identified through regular ophthalmology evaluations and effectively treated in order to avoid damage to vision.

Joint problems

Avascular necrosis of the hip and shoulder joints, in which bone damage occurs due to compromised blood flow due to sickling, can occur later in childhood. This complication can affect an individual's physical abilities and result in substantial pain.

Diagnosis

Inheritance of sickle cell disease or trait cannot be prevented, but it may be predicted. Screening is recommended for individuals in high-risk populations. In the United States, African Americans and Latino Americans have the highest risk of having the disease or trait. Sickle cell is also common among individuals of Mediterranean, Middle Eastern, and Eastern Indian descent.

A complete blood count (CBC) will describe several aspects of an individual's blood cells. A person with sickle cell disease will have a lower than normal hemoglobin level, together with other characteristic red blood cell abnormalities. A hemoglobin electrophoresis is a test that can help identify the types and quantities of hemoglobin made by an individual. This test uses an electric field applied across a slab of gellike material. Hemoglobins migrate through this gel at various rates and to specific locations, depending on their size, shape, and electrical charge. Although sickle hemoglobin (Hb S) and regular adult hemoglobin (called Hb A) differ by only one amino acid, they can be clearly separated using hemoglobin electrophoresis. Isoelectric focusing and high-performance liquid chromatography (HPLC) use similar principles to separate hemoglobins and can be used instead of or in various combinations with hemoglobin electrophoresis to determine the types of hemoglobin present.

Another test called the sickledex can help confirm the presence of sickle hemoglobin, although this test cannot provide accurate or reliable diagnosis when used alone. When Hb S is present, but there is an absence or only a trace of Hb A, sickle cell anemia is a likely diagnosis. Additional beta globin DNA testing, which looks directly at the beta globin gene, can be performed to help confirm the diagnosis and establish the exact genetic type of sickle cell disease. CBC and hemoglobin electrophoresis are also typically used to diagnose sickle cell trait and various other types of beta globin traits.

Diagnosis of sickle cell disease can occur under various circumstances. If an individual has symptoms that are suggestive of this diagnosis, the above-described screening tests can be performed followed by DNA testing, if indicated. Screening at birth using HPLC or a related technique offers the opportunity for early intervention. More than 40 states include sickle cell screening as part of the usual battery of blood tests done for newborns. This allows for early identification and treatment. Hemoglobin trait screening is recommended for any individual of a high-risk ethnic background who may be considering having children. When both members of a couple are found to have sickle cell trait, or other related hemoglobin traits, they can receive genetic counseling regarding the risk of sickle cell disease in their future children and various testing options.

Sickle cell disease can be identified before birth through the use of prenatal diagnosis. Chorionic villus sampling (CVS) can be offered as early as 10 weeks of pregnancy and involves removing a sample of the placenta made by the baby and testing the cells. CVS carries a risk of causing a miscarriage that is between one-half to one percent.

Amniocentesis is generally offered between 15 and 22 weeks of pregnancy, but can sometimes be offered earlier. Two to three tablespoons of the fluid surrounding the baby is removed. This fluid contains fetal cells that can be tested. This test carries a risk of causing a miscarriage, which is not greater than one percent. Pregnant woman and couples may choose prenatal testing in order to prepare for the birth of a baby that may have sickle cell disease. Alternately, knowing the diagnosis during pregnancy allows for the option of pregnancy termination.

Preimplantation genetic diagnosis (PGD) is a relatively new technique that involves in-vitro fertilization followed by genetic testing of one cell from each developing embryo. Only the embryos unaffected by sickle cell disease are transferred back into the uterus. PGD is currently available on a research basis only, and is relatively expensive.

Treatment

There are several practices intended to prevent some of the symptoms and complications of sickle cell disease. These include preventative antibiotics, good hydration, immunizations, and access to comprehensive care. Maintaining good health through adequate nutrition, avoiding stresses and infection, and getting proper rest is also important. Following these guidelines is intended to improve the health of individuals with sickle cell disease.

Penicillin

Infants are typically started on a course of penicillin that extends from infancy to age six. Use of this antibiotic is meant to ward off potentially fatal infections. Infections at any age are treated aggressively with antibiotics. Vaccines for common infections, such as pneumococcal pneumonia, are also recommended.

Pain management

Pain is one of the primary symptoms of sickle cell anemia, and controlling it is an important concern. The methods necessary for pain control are based on individual factors. Some people can gain adequate pain control through over-the-counter oral painkillers (analgesics). Other individuals, or painful events, may require stronger methods that can include administration of narcotics. Alternative therapies may be useful in avoiding or controlling pain, including relaxation, hydration, avoiding extremes of temperature, and the application of local warmth.

Blood transfusions

Blood transfusions are not usually given on a regular basis but are used to treat individuals with frequent and severe painful events, severe anemia, and other emergencies. In some cases blood transfusions are given as a preventative measure, for example to treat spleen enlargement or prevent a second stroke (or a first stroke in an individual shown to be at high risk).

Regular blood transfusions have the potential to decrease formation of hemoglobin S, and reduce associated symptoms. However, there are limitations and risks associated with regular blood transfusions, including the risk of blood-borne infection and sensitization to proteins in the transfused blood that can make future transfusions very difficult. Most importantly, chronic blood transfusions can lead to iron overload. The body tends to store excess iron, such as that received through transfusions, in various organs. Over time, this iron storage can cause damage to various tissues and organs, such as the heart and endocrine organs.

Some of this damage can be prevented by the administration of a medication called desferoxamine that helps the body to eliminate excess iron through the urine. Alternately, some individuals receive a new, non-standard treatment called erythrocytapheresis. This involves the automated removal of sickle cells and is used in conjunction with a reduced number of regular transfusions. This treatment helps to reduce iron overload.

Hydroxyurea

Emphasis is being placed on developing drugs that treat sickle cell anemia directly. The most promising of these drugs in the late 1990s is hydroxyurea, a drug that was originally designed for anticancer treatment. Hydroxyurea has been shown to reduce the frequency of painful crises and acute chest syndrome in adults, and to lessen the need for blood transfusions. Hydroxyurea seems to work by inducing a higher production of fetal hemoglobin. The major side effects of the drug include decreased production of platelets, red blood cells, and certain white blood cells. The effects of long-term hydroxyurea treatment are unknown; however, a nine-year follow-up study of 299 adults with frequent painful crises reported in 2003 that taking hydroxyurea was associated with a 40% reduction in mortality.

Bone marrow transplantation

Bone marrow transplantation has been shown to cure sickle cell anemia in some cases. This treatment is reserved primarily for severely affected children with a healthy donor whose marrow proteins match those of the recipient, namely a brother or sister who has inherited the same tissue type. Indications for a bone marrow transplant are stroke, recurrent acute chest syndrome, and chronic unrelieved pain.

Bone marrow transplantations tend to be the most successful in children; adults have a higher rate of transplant rejection and other complications. There is approximately a 10% fatality rate associated with bone marrow transplants done for sickle cell disease. Survivors face potential long-term complications, such as chronic graft-versus-host disease (an immunemediated attack by the donor marrow against the recipient's tissues), infertility, and development of some forms of cancer. A relatively recent advance in transplantation involves the use of donor stem cells obtained from cord blood, the blood from the placenta that is otherwise discarded following the birth of a new baby. Cord blood cells, as opposed to fully mature bone marrow cells, appear to be less likely to result in graft-versus-host disease in the recipient. This increases the safety and efficacy of the transplant procedure.

Surgery

Certain surgical interventions are utilized in the treatment of specific sickle cell-related complications. Removal of a dysfunctioning gallbladder or spleen can often lead to improvements in health. Investigations are currently underway to establish the efficacy of hip coring surgery, in which a portion of affected bone is removed to treat avascular necrosis of the hip. The hope is that this may provide an effective treatment to alleviate some pain and restore function in the affected hip.

Gene research

Replacing the gene that produces the defective hemoglobin in sickle cell disease patients with one that makes normal hemoglobin may be a possible treatment due to recent research. According to a 1998 report in Science, researchers studied the blood cells from people who carry the sickle cell gene. By using an enzyme called a ribosome, the study was able to alter sickle cells into normal cells. The ribosome cut out the mutated instructions in the cells' genetic pattern and replaced them with the correct instructions. Researchers hope that this will allow the cells to make normal hemoglobin—leading to the ultimate treatment for those with sickle cell disease.

In late 2001, genetic scientists reported that they had designed a gene that might lead to a future treatment of sickle cell anemia. Although the gene had not been tested in humans, early results showed that the injected gene protected cells from sickling. As of 2003,

Key terms

Amino acid — Organic compounds that form the building blocks of protein. There are 20 types of amino acids (eight are "essential amino acids" which the body cannot make and must therefore be obtained from food).

Anemia — A blood condition in which the level of hemoglobin or the number of red blood cells falls below normal values. Common symptoms include paleness, fatigue, and shortness of breath.

Bilirubin — A yellow pigment that is the end result of hemoglobin breakdown. This pigment is metabolized in the liver and excreted from the body through the bile. Bloodstream levels are normally low; however, extensive red cell destruction leads to excessive bilirubin formation and jaundice.

Bone marrow — A spongy tissue located in the hollow centers of certain bones, such as the skull and hip bones. Bone marrow is the site of blood cell generation.

Bone marrow transplantation — A medical procedure used to treat some diseases that arise from defective blood cell formation in the bone marrow. Healthy bone marrow is extracted from a donor to replace the marrow in an ailing individual. Proteins on the surface of bone marrow cells must be identical or very closely matched between a donor and the recipient.

Globin — One of the component protein molecules found in hemoglobin. Normal adult hemoglobin has a pair each of alpha-globin and beta-globin molecules.

Heme — The iron-containing molecule in hemoglobin that serves as the site for oxygen binding.

Hemoglobin — Protein-iron compound in the blood that carries oxygen to the cells and carries carbon dioxide away from the cells.

Hemoglobin A — Normal adult hemoglobin that contains a heme molecule, two alpha-globin molecules, and two beta-globin molecules.

Hemoglobin electrophoresis — A laboratory test that separates molecules based on their size, shape, or electrical charge.

Hemoglobin S — Hemoglobin produced in association with the sickle cell trait; the beta-globin molecules of hemoglobin S are defective.

Hemolytic — Referring to the destruction of the cell membranes of red blood cells, resulting in the release of hemoglobin from the damaged cell.

Hydroxyurea — A drug that has been shown to induce production of fetal hemoglobin. Fetal hemoglobin has a pair of gamma-globin molecules in place of the typical beta-globins of adult hemoglobin. Higher-than-normal levels of fetal hemoglobin can prevent sickling from occurring.

Impotence — The inability to have a penile erection, which can be due to tissue damage resulting from sickling within the penis (priapism).

Iron overload — A side effect of frequent blood transfusions in which the body accumulates abnormally high levels of iron. Iron deposits can form in organs, particularly the heart, and cause life-threatening damage.

Jaundice — Yellowing of the skin or eyes due to excess of bilirubin in the blood.

Magnetic resonance imaging (MRI) — A technique that employs magnetic fields and radio waves to create detailed images of internal body structures and organs, including the brain.

Meniscocytosis — Another word for sickle cell disease.

Mutation — A permanent change in the genetic material that may alter a trait or characteristic of an individual, or manifest as disease, and can be transmitted to offspring.

Narcotics — Strong, prescription medication that can be effective in treating pain, but have the potential to be habit-forming if their use is not supervised correctly.

Nucleic acid — The cellular molecules DNA and RNA that act as coded instructions for the production of proteins and are copied for transmission of inherited traits.

Ophthalmology — The medical specialty of vision and the eye.

Placenta — The organ responsible for oxygen and nutrition exchange between a pregnant mother and her developing baby.

Red blood cell — Hemoglobin-containing blood cells that transport oxygen from the lungs to tissues. In the tissues, the red blood cells exchange their oxygen for carbon dioxide, which is brought back to the lungs to be exhaled.

Screening — Process through which carriers of a trait may be identified within a population.

Sickle cell — A red blood cell that has assumed an elongated shape due to the presence of hemoglobin S.

experiments in gene therapy for sickle cell disease have been carried out in mice, using lentiviral vectors to transfer the corrective gene into the mouse's stem cells. This technique, however, has not yet been attempted in human subjects as of late 2003.

Psychosocial support

As in any lifelong, chronic disease, comprehensive care is important. Assistance with the emotional, social, family-planning, economic, vocational, and other consequences of sickle cell disease can enable affected individuals to better access and benefit from their medical care.

Prognosis

Sickle cell disease is characteristically variable between and within affected individuals. Predicting the course of the disorder based solely on genes is not possible. Several factors aside from genetic inheritance determine the prognosis for affected individuals, including the frequency, severity, and nature of specific complications in any given individual. The availability and access of comprehensive medical care also plays an important role in preventing and treating serious, acute complications, which cause the majority of sickle cell-related deaths. For those individuals who do not experience such acute events, life expectancy is probably substantially greater than the average for all people with sickle cell disease. The impact of recent medical advances supports the hypothesis that current life expectancies may be significantly greater than those estimated in the early 1990s. At that time, individuals with SS disease lived to the early- to mid-40s, and those with SC disease lived into the upper 50s on average. As of 2003, the life expectancy of persons with SS is over 50. With early detection and comprehensive medical care, most people with sickle cell disease are in fairly good health most of the time. Most individuals can be expected to live well into adulthood, enjoying an improved quality of life including the ability to choose a variety of education, career, and family-planning options for themselves.

Resources

Books

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Anemias Caused by Excessive Hemolysis: Sickle Cell Diseases." Section 11, Chapter 127 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Pregnancy Complicated by Disease: Hemoglobinopathies." Section 18, Chapter 251 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Periodicals

Davies, S. C., and A. Gilmore. "The Role of Hydroxyurea in the Management of Sickle Cell Disease." Blood Reviews 17 (June 2003): 99-109.

Egbert Maikler, Virginia, et al. "Children's and Adolescents' Use of Diaries for Sickle Cell Pain." Journal of the Society of Pediatric Nurses 6, no. 4 (October—December 2001): 161-169.

Harris, Leslie. "Living Well with Sickle Cell." Essence September 1999: 58.

Nienhuis,A. W., H. Hanawa, N. Sawai, et al. "Development of Gene Therapy for Hemoglobin Disorders." Annals of the New York Academy of Science 996 (May 2003): 101-111.

Seppa, N. "Gene Therapy for Sickle-cell Disease?" Science News 160, no. 24 (December 15, 2001): 372.

Steinberg, M. H., F. Barton, O. Castro, et al. "Effect of Hydroxyurea on Mortality and Morbidity in Adult Sickle Cell Anemia: Risks and Benefits up to 9 Years of Treatment." Journal of the American Medical Association 289 (April 2, 2003): 1645-1651.

Winrow, N., and E. R. Melhem. "Sickle Cell Disease and Stroke in a Pediatric Population. Evidence-Based Diagnostic Evaluation." Neuroimaging Clinics of North America 13 (May 2003): 185-196.

Yerys, B. E., D. A. White, C. F. Salorio, et al. "Memory Strategy Training in Children with Cerebral Infarcts Related to Sickle Cell Disease." Journal of Pediatric Hematology and Oncology 25 (June 2003): 495-498.

Organizations

Mayo Foundation for Medical Education and Research. http://www.mayohealth.org.

Sickle Cell Disease Association of America. 200 Corporate Point, Suite 495, Culver City, CA 90230-7633. (310) 216-6363. (800) 421-8453. 〈http://sicklecelldisease.org/〉.

Sickle Cell Disease Program, Division of Blood Diseases and Resources. National Heart, Lung, and Blood Institute. II Rockledge Centre, 6701 Rockledge Dr. MSC 7950, Bethesda, MD 20892-7950. (301) 435-0055.

sickle cell

a crescentic or sickle-shaped erythrocyte, the abnormal shape caused by the presence of varying proportions of hemoglobin S. See illustration at cell.

sickle cell anemia an autosomal dominant, chronic form of hemolytic anemia in which large numbers of sickle cells circulate in the blood; it is most common among persons of African and Mediterranean descent. Persons genetically homozygous have 85 to 95 per cent sickle cells and have the full-blown condition; see sickle cell disease. Those who are heterozygous are usually asymptomatic.

sickle cell crisis a broad term describing several different acute conditions occurring as part of sickle cell disease, such as aplastic crisis, hemolytic crisis, and vaso-occlusive crisis.

sickle cell disease any of the diseases associated with the presence of hemoglobin S, including sickle cell anemia, sickle cell–thalassemia, and the conditions called sickle cell–hemoglobin C and D disease. They are found most often in those of black African descent, but they also occur in persons of Mediterranean (Southern European and North African), Middle Eastern, or Asian Indian ancestry. About 8 to 10 per cent of all African Americans carry the sickle cell gene. About 90 per cent of persons with the gene are heterozygous for it, simply carriers of the sickle cell trait and usually without symptoms. The remainder, or about 1 in 500 of an ethnic group where the gene occurs, are homozygous for hemoglobin S, actually having sickle cell disease and suffering from the effects of hemolysis.

Sickle cell disease is a serious, hereditary, chronic disease in which the red blood cells have reduced life span and are rigid, with a crescent or sickle shape. The shape is the result of an abnormality in the hemoglobin, which alters the deformability of the cells under conditions of low oxygen tension. Because of their distorted shape the cells have difficulty passing through the small arterioles and capillaries and have a tendency to clump together and occlude the blood vessel. Some scientists believe that sickle cell disease developed as a defense against malaria. Malarial parasites do not grow in erythrocytes containing hemoglobin S. Therefore, carriers (heterozygotes) have an advantage in areas where malaria is prevalent (called the heterozygote advantage). (See accompanying figure.)

Symptoms. There are many symptoms of sickle cell disease, all of them related to the defective hemoglobin and its effect on red blood cells. Some persons with the condition suffer from only a few symptoms, while others are severely affected and have a short life span. Better understanding and management of the disease in recent decades has improved the prognoses for patients with it.

The major symptoms are anemia, periodic joint and limb pain and sometimes edema of the joints, chronic ulceration about the ankles, episodes of severe abdominal pain with vomiting, and abdominal distention. The spleen becomes infarcted so that it is essentially absent and predisposes the patient to infection with encapsulated organisms. Bone changes often can be seen on x-ray and are due to bone infarcts. Headache, paralysis, and convulsions may result from cerebral thrombosis, which can cause stroke, blindness, and other neurological disturbances. There is a tendency toward progressive renal disease and renal failure.

Sickle cell crisis is a broad term that describes several different conditions, particularly aplastic crisis, which is temporary bone marrow aplasia; hemolytic crisis, which is acute red cell destruction, leading to jaundice; and vaso-occlusive crisis, which is severe pain due to infarctions located in the bones, joints, lungs, liver, spleen, kidney, eye, or central nervous system. Factors that precipitate a crisis include infection, dehydration, trauma, strenuous physical exertion, emotional stress, and extremes of heat and cold.

Treatment and Care. There is no cure for sickle cell disease. Treatment is symptomatic; preventive measures are employed to reduce the incidence of crises and to avoid infections. It is also important that the patient receive all available immunizing agents. Nutritional deficiencies should be corrected when present (folate supplementation is especially important), and then a well-balanced dietary intake should be maintained. hydroxyurea and prophylactic penicillin are administered according to therapeutic guidelines. Social service programs are required to facilitate adjustment to the disease and its sequelae. Control of pain associated with this condition should be a priority.

Patient Care.

Sickle cell disease is a chronic condition with acute episodes related to vaso-occlusion. Virtually every system of the body can be affected by the ischemia resulting from obstruction of the blood vessels by clumps of deformed erythrocytes. Among the more common acute complications are inflammation of fingers and toes, aplastic anemia, splenic sequestration, and stroke. Chronic disorders include leg ulcers, renal complications, aseptic necrosis, and retinopathy. Bacterial infection is one of the major causes of morbidity and mortality in patients with sickle cell disease.

Because of the potential for serious complications due to occlusion of blood vessels, patients with sickle cell disease should have regular physical examinations to detect early changes. Periodic eye examinations are necessary to monitor retinal changes due to vaso-occlusion of retinal vessels.

Measures to improve or maintain the general well-being of patients include preventing dehydration, maintaining adequate nutrition to optimize the patient's resistance to infection and resources for healing, and managing the anemia that is characteristic of sickle cell disease. Education of patients and their parents and family members is an essential component of care. Patient support groups can be an effective mechanism to diffuse fear. Guidelines for the management of acute and chronic pain are available from the American Pain Society. A comprehensive biopsychosocial clinical assessment should be performed at least yearly.

The National Heart, Lung, and Blood Institute of NIH has published a guide called NIH Management and Therapy of Sickle Cell Disease. A printed copy is available as NIH publication number 95-2117. The guidelines are available online at http://www.emory.edu/peds/sickle/nih1/htm.

Clinicopathologic findings in sickle cell anemia. The findings are a consequence of infarctions, anemia, hemolysis, and recurrent infection. From Damjanov, 2000.

Statistical probabilities of inheriting sickle cell anemia.

sickle cell disorders any blood disorders associated with the presence of hemoglobin S, including the sickle cell diseases and sickle cell trait.

sick·le cell a·ne·mi·a

[MIM*603903]

an autosomal recessive anemia characterized by crescent- or sickle-shaped erythrocytes and accelerated hemolysis, due to substitution of a single amino acid (valine for glutamic acid) in the sixth position of the β-chain of hemoglobin, the gene of which is on chromosome 11; affected homozygotes have 85-95% hemoglobin (Hb) S and severe anemia, whereas heterozygotes (said to have sickle cell trait) have 40-45% Hb S, the rest being normal Hb A; low oxygen tension causes polymerization of the abnormal β-chains, thus distorting the shape of the red blood cells to the sickle form. Homozygotes develop "crisis" episodes of severe pain due to microvascular occlusions, bone infarcts, leg ulcers, and atrophy of the spleen associated with increased susceptibility to bacterial infections, especially streptococcal pneumonia. Occurs most commonly in people of African descent.

Synonym(s): drepanocytic anemia, sickle cell disease

Farlex Partner Medical Dictionary © Farlex 2012

sickle cell disease

Any syndrome associated with sickle cells (e.g., sickle cell anaemia, haemoglobin genotype S/S, sickle cell-HbC disease and sickle cell-β-thalassaemia).

Management
Allogeneic BMTP may be curative in young patients with symptomatic SCD.

sickle cell disease

Any syndrome associated with sickle cells–eg, sickle cell anemia–hemoglobin genotype S/S, sickle cell-HbC disease, sickle cell-β-thalassemia Management Allogeneic BMTP may be curative in young Pts with symptomatic SCD. See Sickle cell anemia.

sick·le cell a·ne·mi·a

(sik'ĕl sel ă-nē'mē-ă)

An autosomal dominant anemia characterized by crescentic or sickle-shaped erythrocytes and by accelerated hemolysis, due to substitution of a single amino acid (valine for glutamic acid) in the sixth position of the beta chain of hemoglobin (Hb); affected homozygotes have 85-95% Hb S and severe anemia, whereas heterozygotes (said to have sickle cell trait) have 40-45% Hb S, the rest being normal Hb A; low oxygen tension causes polymerization of the abnormal beta chains, thus distorting the shape of the red blood cells to the sickle form. Homozygotes develop "crises": episodes of severe pain due to microvascular occlusions, bone infarcts, leg ulcers, and atrophy of the spleen associated with increased susceptibility to bacterial infections, especially streptococcal pneumonia. Occurs almost exclusively in blacks.
Synonym(s): crescent cell anemia, drepanocytic anemia, sickle cell disease.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Sickle Cell Disease

DRG Category:	812
Mean LOS:	3.4 days
Description:	MEDICAL: Red Blood Cell Disorders Without Major CC

Sickle cell disease (SCD) is a genetic autosomal recessive disorder that results in abnormalities of the globin genes of the hemoglobin molecule of the red blood cells (RBCs). It is more common in African Americans than in other groups in the United States. It can be in the form of sickle cell anemia or either sickle cell thalassemia or sickle cell hemoglobin (Hb) C. Sickle cell anemia, the severest of the sickle cell disorders, is homozygous and has no known cure. Sickle cell trait occurs when a child inherits normal Hb from one parent and Hb S (the abnormal Hb) from the other; people with the sickle cell trait are carriers only and rarely manifest the clinical signs of the disorder.

The RBCs that contain more Hb S than Hb A are prone to sickling when they are exposed to decreased oxygen tension in the blood. The cells become more elongated, thus the term “sickle.” Once sickled, RBCs are more rigid, fragile, and rapidly destroyed. The RBCs therefore have a short survival time (30 to 40 days, as compared with a normal 120-day survival rate), a decreased oxygen-carrying capacity, and low Hb content. They cannot flow easily through tiny capillary beds and may become clumped and cause obstructions. The obstructions can lead to ischemia and necrosis, which produce the major clinical manifestations of pain. In people with SCD, approximately 50% do not survive beyond age 20, and most people do not live past age 50. Complications include chronic obstructive pulmonary disease, congestive heart failure, and infarction of organs such as the spleen, retina, kidneys, and even the brain.

Causes

Two factors have been identified as producing sickling, although the exact cause is unknown. The first is hypoxemia, which is caused by low oxygen tension in the blood from high altitudes, strenuous exercise, or low oxygen concentration during anesthesia. The second is a change in the condition of the blood, such as decreased plasma volume, decreased blood pH, or increased plasma osmolality as a result of dehydration.

Genetic considerations

Sickle cell anemia is the result of mutant beta globin in which the mutation causes aggregation of Hb and sickling of RBCs. Sickle cell anemia (also known as homozygous sickle cell disease and Hb SS) accounts for 60% to 70% of sickle cell disease in the United States. SCD may also result from co-inheritance of the Hb S mutation with another abnormal Hb variant. These include Hb C (E6K mutation): sickle-Hb C disease (Hb SC); and beta-thalassemia mutations: Sβ+-thalassemia and Sβ°-thalassemia; as well as Hb D (D-Punjab; E121Q mutation) or Hb O (O-Arab; E121K mutation). The C allele of BCL1lA is associated with reduced severity of sickle cell anemia, likely because of increased production of fetal hemoglobin.

Gender, ethnic/racial, and life span considerations

Clinical symptoms rarely appear before the child is 6 months old and occur in both boys and girls. Sickle cell occurs most frequently in African Americans but also occurs in African, Mediterranean, Caribbean, Middle Eastern, and Central American populations. Approximately 1 of 12 African Americans has sickle cell trait. The sickle gene is present in approximately 8% of African Americans, and thus approximately 2 million people in the United States have sickle cell trait.

Global health considerations

SCD is most commonly found in people with ancestry in sub-Saharan Africa. It is also found in the Mediterranean region and India. Experts suspect that this geographic concentration is related to the survival advantage during malaria epidemics.

Assessment

History

Most infants do not develop symptoms during the first 6 months because fetal Hb has a protective effect. The parents or the child may describe a history of lung infections or cardiomegaly (hypertrophy of the heart). Children with the disease may have a history of chronic fatigue, dyspnea, joint pain and swelling, and chest pain.

Physical examination

The most common symptoms are a result of a vaso-occlusive crisis: sudden pain in the abdomen, soft tissues, bones, and joints and swelling of the hands and feet. The extent of the symptoms depends on the amount of Hb S that is present. The general signs are similar to the other types of hemolytic anemia (anemia as a result of destruction of RBCs): malaise, fatigue, pallor, jaundice, and irritability. Children begin to fall below the growth curve in height and weight at around 7 years, and puberty is usually delayed. They are often small for their age and may have narrow shoulders and hips, long extremities, and a curved spine. You may note jaundice and pale skin. Often, the children have heart rates that are faster than normal and heart murmurs; you may find a large liver and spleen. Eventually, all body systems, including the heart, lungs, central nervous system, kidneys, liver, bones and joints, skin, and eyes, are affected. The most severe problem is sickle cell crisis (Table 1).

Sickle Cell CrisisSickle cell crisis may be preceded by a recent infection or a stressor such as dehydration, strenuous activity, or high altitude. Other assessment findings include changes in mental status, such as sleepiness, listlessness, and irritability. Fever; severe pain; bloody urine; and pallor of the lips, tongue, palms, and nails may also occur.

Table 1. Sickle Cell Crisis
TYPE/DESCRIPTION	SYMPTOMS
Vaso-occlusive crisis: Most common type; usually appears after age 5; the result of sickling in the microcirculation that leads to vasospasm, thrombosis, and local infection	Severe pain: Joint, abdominal, muscle, and thoracic; jaundice; dark urine; fever; elevated white blood cell (WBC) count; lethargy; fatigue; sleepiness
Sequestration crisis: Occurs in infants between 8 and 24 mo; massive pooling of RBCs in the liver and spleen	Lethargy, pale skin, hypovolemia, tachycardia, cool extremities, dropping urinary output, delayed capillary refill
Aplastic crisis: Results from bone marrow depression and is associated with viral infections; leads to compensatory increase in RBCs and RBC lysis	Lethargy, pale skin, shortness of breath, altered mental status, sleepiness
Hyperhemolytic crisis: Rare; result of certain medications or infections	Abdominal distension, jaundice, dark urine

Psychosocial

Children with SCD have a chronic, potentially fatal genetic disorder. Frequent hospitalizations and delayed growth and development put them at risk for low self-esteem and body image problems. In addition, because of the genetic nature of the disease, parents may experience guilt feelings. Families need extensive genetic and psychological counseling to avoid problems. Assess the child and the family for coping skills and knowledge deficits about the cause and prevention of sickle cell crisis.

Diagnostic highlights

Test	Normal Result	Abnormality With Condition	Explanation
Genetic testing	Negative	Mutant gene	Identifies expressed mutations in single genes
Peripheral blood smear	Normal RBCs	Classic distorted, sickle-shaped RBCs	RBCs have a characteristic sickle shape caused by structurally abnormal Hb molecules
Hb electrophoresis	No Hb S	Presence of Hb S	Identifies SCD by identifying Hb S; a stained blood smear can show sickling cells
Complete blood count	RBCs: 4–5.5 million/μL; hemoglobin: 12–18 g/dL	Decreased, generally 5–10 g/dL; chronic neutrophilia	Chronic hemolytic anemia leads to decreased RBCs
	WBCs: 4,500–11,000/μL	Chronic neutrophilia is often present with leukocytosis	Elevation in the WBC count (> 20,000 per mm3) with left shift indicates infection
	Platelets: 150,000–400,000/μL	Often increased	Spleen function may be reduced, leading to a reduction in platelet destruction

Primary nursing diagnosis

Diagnosis

Altered growth and development related to physical disabilities secondary to poor tissue perfusion

Outcomes

Child development; Physical maturation; Caregiver–patient relationship; Parenting; Psychosocial adjustment

Interventions

Nutritional monitoring; Nutrition therapy; Self-responsibility facilitation; Developmental enhancement; Counseling; Caregiver support

Planning and implementation

Collaborative

Although SCD cannot be cured, there are many treatment alternatives to prevent exacerbations, limit complications, and manage sickle cell crises. Medical management centers on the treatment of anemia and the prevention of crisis. Families are counseled to avoid the causes of crisis (dehydration, infection, hypoxia, high altitudes, vigorous exercise, and stress). To prevent aplastic crisis, prophylactic daily doses of penicillin are given to infants beginning when they are about 4 months old.

Sequestration and aplastic crises are treated with oxygen if they are hypoxemic, intravenous fluids, transfusions of packed RBCs, and bronchodilators if needed. A vaso-occlusive crisis is treated with analgesia and increased hydration. Pain levels should be assessed frequently and corrected quickly. Avoid using aspirin, which may increase acidosis. Children may not express the need for pain medication because of fear of the route of administration. Patient-controlled analgesia, therefore, may be used, with morphine sulfate as the drug of choice. Iron supplements may be used if folic acid levels are lower than normal. Infections are treated with appropriate antibiotics.

Pharmacologic highlights

Medication or Drug Class	Dosage	Description	Rationale
Hydroxyurea (Hydrea)	Initial: 10 mg/kg After 6 wk: 15 mg/kg Goal: Maximally tolerated dose up to 35 mg/kg without signs of toxicity	Antimetabolite	Inhibits production of Hb F, which inhibits sickling
Analgesia	Varies by drug	Morphine sulfate, meperidine (Demerol), ketorolac (Toradol)	Relieves pain

Independent

Counsel children and families on the importance of maintaining hydration even when the child is ill and during hot weather. Encourage oral fluid intake in addition to intravenous fluids when children are in the hospital. Increase fluid intake to 1.5 times the normal maintenance volume if the child’s cardiac function is adequate.

In cases of acute crisis, pain is the overriding problem. In addition to prescription medicines, employ other pain-reducing interventions, such as diversion, imagery, and general comfort measures. Keep the pain level within tolerable limits for the individual. Encourage families to maintain a normal life for the child with SCD. Arrange for genetic counseling so that families can make informed decisions. When appropriate, and depending on the age, include siblings in the care.

Evidence-Based Practice and Health Policy

Gold, J.I., Treadwell, M., Weissman, L., & Vichinsky, E. (2011). The mediating effects of family functioning on psychosocial outcomes in healthy siblings of children with sickle cell disease. Pediatric Blood & Cancer, 57(6), 1055–1061.

Family functioning plays a critical role in the health and well-being of children with chronic illnesses. In a study among 65 healthy siblings of children with SCD, an increased number of emergency department (ED) visits predicted poor psychological adjustment in the siblings (p < 0.05).
The children with SCD visited the ED an average of 1.94 times and were hospitalized an average of 1.82 times (range, 0 to 8 times) for a mean of 8.6 days during the year prior to the study. Twenty percent of the children with SCD had experienced a stroke and were receiving chronic transfusion therapy.
Family functioning mediated the effect that ED visits had on sibling adjustment. In fact, higher levels of family expressiveness and family support were associated with significant improvements in psychological adjustment among the siblings (p < 0.01 and p < 0.001, respectively).

Documentation guidelines

Response to pain medication and other pain-reduction methods
Physical findings of pain: Location and duration
Response to hydration methods
Presence of complications: Unresolved pain, cerebrovascular accident, kidney impairment

Discharge and home healthcare guidelines

Teach the patient and family the causes, signs, and symptoms of crisis and ways to avoid future crisis. Emphasize good nutrition and the avoidance of caffeine and smoking. Patients and families need to be taught the signs and symptoms of complications, such as cardiopulmonary dysfunction, increased intracranial pressure, and renal impairment. The patient and family need to be taught the importance of taking daily antibiotics and the side effects, dosage, and route of medication. If the patient is on pain medications, care should be taken to ensure that the medication is not abused but is taken when the patient is in need. Patients and families need to understand the need for genetic counseling, the potential long-term effects of SCD, and the possible complications. Older children and parents need to deal with the delayed sexual maturity that occurs. Long-term follow-up care is essential for patients with SCD. Refer patients to the Web site for the Sickle Cell Disease Association of America (http://www.sicklecelldisease.org) for patient and family information.

Patient discussion about sickle cell disease

Q. Please precribe for me the possible medicine (treatment) for sickle cells. Secondly, my boy lost hearing at 4 1- I need to know how sickle cells can be treated. 2- My boy just surprisingly lost his abillity to hear anything at the age of 4.

A. wow...you are going through some hard times...it's the hardest thing in the world seeing your children in pain. loosing his hearing could be caused by clots that were formed and destroyed the ear nerve. but it's unlikely it happened in both ears...so i would check it out. and about treatment- there are a variety of treatments, so i found a web site with them all. and even some that are still in research: http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_Treatments.html

More discussions about sickle cell disease

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References in periodicals archive ?

'Indeed, early detection of sickle cell disease combined with appropriate medical care can improve the quality of life and the life expectancy of the patients.,' he added.

CARIBBEAN-HEALTH-New project to detect sickle cell in new born babies in OECS

is committed to transforming the lives of people with sickle cell disease and other serious hemoglobinopathies, including beta thalassemia, by developing oral small molecule therapeutics that are designed to be easy to administer and use across the world.

Imara Presents Positive, Interim Phase 2a Data on IMR-687 for the Treatment of Sickle Cell Disease

Manifestations of sickle cell disease on thoracic imaging.

ANEMIA DE CELULAS FALCIFORMES: CORRELACION CLINICO-PATOLOGICA

The haemoglobin level, total erythrocytes count ([10.sup.6]/[micro]), mean cell haemoglobin concentration (g/dl), mean cell volume (fl), packed cell volume (%), mean cell haemoglobin (pg), total leukocytes count ([10.sup.3]/[micro]l) and platelet count ([10.sup.3]/[micro]l) of sickle cell disease is shown in Table 1

FREQUENCY OF SICKLE CELL ANAEMIA AND SICKLE CELL TRAIT IN PATIENTS REFERRED TO HEGLIG HOSPITAL IN WESTERN KORDOFAN STATE (SUDAN)

Red blood cell antigen genotyping for sickle cell disease, thalassemia, and other transfusion complications.

Hyperhemolysis Syndrome in Patients With Sickle Cell Disease

Sickle Cell Disease (SCD) is one of the most important genetic diseases in the world.

Prevalence of depression among adults with sickle cell disease in the Southern Region of Saudi Arabia

Sickle cell disease is a type of anemia that is most common among black people.

Funding needed for sickle cell research

FDA approves new treatment for sickle cell disease. [Online] 2017 [Cited 2017 Aug 14].

L-Glutamine approved for use in patients with sickle cell disease

"Sickle cell disease affects millions of people worldwide and is an emerging global health burden," said George Murphy of BUSM, who is leading the project.

Creating world's largest Sickle cell disease stem cell library

"A person suffering from sickle cell disease who is living a productive life is better than a person who is healthy but is putting obstacles in his life," said the visiting expert.

Sickle cell drive 'major success'

Sickle cell disease is a group of inherited red blood cell disorders that affect millions of persons worldwide.

World Sickle Cell Day--June 19, 2016

Global Markets Direct's, 'Sickle Cell Disease - Pipeline Review, H1 2016', provides an overview of the Sickle Cell Disease pipeline landscape.