Spherocytic anemia

Description, Causes and Risk Factors:Spherocytic anemia is the most common hereditary hemolytic anemia among people of Northern European. The incidence of the disorder is approximately 1 in 5000 people. Spherocytic anemia usually is transmitted as an autosomal dominant trait in 75% and 25% of all spherocytic anemia is autosomal recessive.Spherocytic anemia is an inherited abnormality of red cell shape and results from defective interactions amongst the components of the cytoskeleton. It is known that spectrin/actin dissociates in low ionic strength media from ghosts and cytoskeletons at a rate which is slower for spherocytic anemia than normal preparations. Hybridization experiments have established that this behavior is not due to a defective spectrin or actin but resides in a spectrin-binding component of the membrane.The network of cytoskeletal protein which lines the cytoplasmic face of the erythrocyte membrane is believed to control the shape and deformability of the cell. It has been proposed that intrinsic defects in cytoskeletal components may lead to abnormalities in cell shape, and some evidence supports this view. For example, dimeric spectrin prepared from erythrocytes of patients affected with hereditary elliptocytosis and hereditary pyropoikilocytosis exhibit a reduced ability to form tetramers and higher oligomers both in solution and on the membrane. This reduced ability of spectrin to self-associate may result in a membrane abnormally rich in spectrin dimers rather than tetramers with resulting cytoskeletal instability. In the case of hereditary pyropoikilocytosis, a proteolytic fragment from the terminus of the spectrin a chain (band 1), thought to be involved in the interaction site between dimers, had a peptide map which was different from the same fragment from the normal polypeptide. HS is another example of a shape defect in erythrocytes and recent research has focused on the role of the cytoskeleton in this disease. It is concluded that approximately 40% of spectrin is defective in some spherocytic anemia kindreds and cannot bind to the spectrin-binding protein band 4.1. Researchers also proposed a defect near the N-terminal end of the spectrin, B chain which caused a 50% reduction in its ability to bind band 4.1, but such behavior was found in only a subset of spherocytic anemia patients. Taken together these observations suggest that the spherocytic anemia population may be heterogenous and consist of several perhaps distinct subgroups.The abnormal red cell morphology, which results in shortened cell survival, is due to a deficiency of, or a dysfunction in, spectrin, ankyrin, band 3 and or protein 4.2. Spectrin deficiency is the most common defect. A variety of mutations have been noted in genes encoding these membrane proteins. The genes responsible are localized on chromosomes 1, 2, 8, 15 and 17 for membrane proteins. Most cases of spherocytic anemia are heterozygous because homozygous states are lethal. In pedigrees that have a dominant defect, affected family members tend to have similar degrees of hemolysis and clinical severity. Severe hemolytic anemia is often associated with a greater reduction of the affected membrane proteins. There is an apparent correlation between clinical and protein phenotypes.Symptoms:Patients with spherocytic anemia generally have a mild to moderately severe chronic hemolytic anemia. Many patients are asymptomatic, with only slightly reduced hemoglobin values, rare clinical problems, and a normal physical examination except for slight splenomegaly. Other children, however, have fatigue, decreased exercise tolerance, periodic jaundice, and episodes of more severe anemia which require monitoring and occasionally blood transfusions.Infants may have yellowing of the skin and eyes (jaundice) and pale coloring (pallor).Other symptoms may include:
  • Fatigue.
  • Irritability.
  • Shortness of breath.
  • Weakness.
Diagnosis:Differential Diagnosis:
  • Thalassaemia.
  • G6PD deficiency anemia.
  • Sickle cell anemia.
  • Autoimmune hemolytic anemia.
  • Hereditary elliptocytosis.
  • Pyruvate kinase deficiency.
  • Chronic malaria.
The diagnosis of spherocytic anemia can be made when there is a consistent history and there are numerous microspherocytes on a blood smear. In some children the hemoglobin concentration is in the normal range. In most children the anemia is only mild, with hemoglobin values between 9 and 11.5 gm/dL. Even though the spherocytes exhibit decreased diameter, their volume (i.e., MCV) is normal. The MCHC mean corpuscular hemoglobin concentration) may be slightly elevated (35 to 37 gm/dL) in some cases. The reticulocyte count is nearly always elevated in the 3 - 15% range. WBC and platelet counts are normal.The diagnosis is strengthened or confirmed by documentation of a positive family history and/or abnormal (increased) incubated osmotic fragility test, which is essentially a quantitative measure of spherocytes. Occasionally it is necessary to exclude other conditions in which spherocytes may be observed on the blood smear, such as Coombs positive autoimmune hemolytic anemia. Other abnormal test results include slight elevation in total and indirect bilirubin and decreased haptoglobin, which are features of any hemolytic anemia.If further testing is required a screening test with high predictive value for spherocytic anemia should be performed. The recommended screening tests are the EMA binding test and the cryohemolysis test. The usefulness of each can be improved when the results are interpreted in conjunction with clinical information and red cell indices.Treatment:The treatment options of spherocytic anemia involve:
  • Pre-splenectomy care.
  • Splenectomy.
  • Post-splenectomy complications.
Most patients with spherocytic anemia are well and require no treatment. Supplemental iron, folic acid, or special diets are unnecessary. A complete blood count need not be performed on a routine basis more than once or twice annually. Any time that a patient has a particularly severe infection or has marked pallor, increasing jaundice, or other evidence of an aplastic or hyperhemolytic crisis, an additional CBC and reticulocyte count should be performed. A packed red blood cell transfusion should be considered for symptomatic patients with symptomatic anemia. No restriction of activities is necessary, even in patients with splenomegaly. Unlike conditions such as infectious mononucleosis where the spleen is acutely enlarged, there is no evidence that chronic splenomegaly predisposes to splenic rupture.Children who are candidates for splenectomy include those with severe spherocytic anemia requiring red cell transfusions and those with moderate spherocytic anemia who manifest growth failure or other signs and symptoms of anemia. Splenectomy for children with spherocytic anemia should be performed when the child is older than 6 years. Another interesting approach has been the use of partial splenectomy to retain splenic immunologic function while at the same time reducing the rate of hemolysis.Splenectomy is almost always delayed until beyond 5 or 6 years of age, when the risk of post-splenectomy septicemia is somewhat less. However, there is a small risk of this fatal complication even in older children, teenagers, and adults. Therefore, the advantages of splenectomy (resolution of the anemia and of all of its complications, such as gallstones and aplastic or hyperhemolytic crises) must be weighed against the risk of post-splenectomy septicemia.A second complication of splenectomy that is less well defined is thrombosis. There is emerging evidence that persons who have a splenectomy are predisposed to developing blood clots in their legs, lungs, heart, and brain. This is unproven and currently under study by researchers.NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care. 


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