sickle cell

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Related to crescent cell: sickle cell trait, crescent cell anemia

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

an abnormal, crescentic erythrocyte that is characteristic of sickle cell anemia, resulting from an inherited abnormality of hemoglobin (hemoglobin S) causing decreased solubility at low oxygen tension.

sickle cell

n.
An abnormal, crescent-shaped red blood cell that results from a single change in the amino acid sequence of the cell's hemoglobin, which causes the cell to contort, especially under low-oxygen conditions.

sickle cell

Etymology: AS, sicol, crescent; L, cella, storeroom
an abnormal crescent-shaped red blood cell containing hemoglobin S, characteristic of sickle cell anemia. Also called drepanocyte.
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Sickle cell

sickle cell

A crescent-shaped, holly-leaf-/scythe-like RBC caused by polymerisation or sickling of haemoglobin (Hb S) or other “sickling” Hbs, which occurs more readily with decreased pH, decreased O2, increased temperature and increased osmolarity.

sick·le cell

(sik'ĕl sel)
An abnormal, crescentic erythrocyte characteristic of sickle cell anemia, resulting from an inherited abnormality of hemoglobin (hemoglobin S) that causes decreased solubility at low oxygen tension.
See also: sicklemia, sickling
Synonym(s): drepanocyte.
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SICKLED CELLS IN SICKLE CELL DISEASE

sickle cell

An abnormal erythrocyte shaped like a sickle. Synonym: drepanocyte See: anemia, sickle cell
illustration
See also: cell

Sickle cell

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

sickle cell

a crescentic or sickle-shaped erythrocyte. In humans, the abnormal shape is caused by a structural hemoglobinopathy. Sickle cells are found in normal members of the family Cervidae (deer).

Patient discussion about sickle cell

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

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