Spherocytosis, Type I

Alternative Names

  • Spherocytosis, Hereditary, 1
  • HS1
  • SPH
  • HS
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WHO-ICD-10 version:2010

Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism

Haemolytic anaemias

OMIM Number

182900

Mode of Inheritance

Autosomal dominant, autosomal recessive

Gene Map Locus

8p11.21

Description

Hereditary Spherocytosis (HS) is an intrinsic red blood cell defect, resulting in hemolytic anemia. The disease is characterized by the presence of spheroid erythrocytes, which have increased osmotic and mechanical fragility. The underlying cause of this condition is the defects in the RBC membrane cytoskeleton. There is a wide amount of clinical variability among patients with this condition, ranging from asymptomatic condition to life threatening anemia. About 65% of affected neonates show some symptoms of the condition. All affected neonates present with neonatal jaundice. Among adults, the common symptoms of HS are anemia, mild pallor, jaundice, and splenomegaly.

Diagnosis is based on clinical symptoms, and includes results of tests such as complete blood count, Coombs' Test, osmotic fragility test, blood smears, and reticulocyte counts. HS is frequently complicated by gallstones, gall-bladder disease, hemochromatosis, and crises.

One of the major modes of treatment from spherocytosis is through splenectomy. This is because the deformed erythrocytes have a tendency to be selectively trapped in the spleen and destroyed. Splenectomy markedly abrogates hemolysis. All affected patients should be routinely assessed for gallstones. Prognosis after splenectomy is good.

Spherocytosis type I is associated with mutations in Ankyrin 1 (ANK1) gene .

Molecular Genetics

HS can be caused by mutations in at least one of the following genes; ANK1 (Ankyrin 1), EPB3 (Erythroid Protein Band 3), SPTB (Spectrin, Beta. Erythrocytic), EPB42 (Protein 4.2, Erythrocytic) and the SPTA1 (Spectrin, Alpha, Erythrocytic) genes. More than two-thirds of HS patients have a combined spectrin and ankyrin deficiency. At least 55 mutations in the ANK1 gene have been found to cause Hereditary Spherocytosis.

The Ankyrin protein is primarily expressed in the erythrocytes, but it is also found in muscle and brain cells. In the erythrocytes, the protein is located at the cell membrane, where it binds to other membrane proteins. The binding of membrane proteins to one another maintains the stability and structure of red blood cells but also allows for their flexibility. The proteins allow the cell to change shape without breaking when passing through narrow blood vessels.

Epidemiology in the Arab World

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Other Reports

Algeria

Zerhouni et al. (1991) conducted a survey of more than 12,000 persons referred to a hematological outpatient clinic in Algiers and estimated that the incidence of hereditary spherocytosis is 1/1000. Another 9 cases were found in nine of the corresponding families. Anemia was present in 81% of the subjects. The transmission was dominant in five of eight informative families (63%). No firm conclusion could be reached concerning the amount of spectrin and ankyrin in nine families; however, two-dimensional peptide maps ruled out any alpha II domain abnormality in these families.

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