Typical dominant HS is most commonly caused by deficiency of

 # Typical dominant HS is most commonly caused by deficiency of: 

a. Ankyrin 

b. Band 3 

c. Spectrin 

d. Protein 4.2

The correct answer is A. Ankyrin.

The most common cause of typical dominant HS (2/3rd of cases) is ankyrin defect. Band 3 defect and isolated spectrin deficiency is next common. The degree of spectrin deficiency correlates with spheroidicity, ability of red cells to withstand shear stress, degree of hemolysis and response to 

splenectomy. Protein 4.2 deficiency is inherited as autosomal recessive trait. Severe HS almost always have recessive inheritance and most have severe spectrin deficiency (< 40%) may be d/t defect in β-spectrin. 

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