Hemoglobin C Disease

Excerpt

The normal adult hemoglobin is a hetero-tetramer consisting of two pairs of globin polypeptide chains: one pair of alpha chains and the next pair of non-alpha chains. These polypeptide chains are folded such that the four heme groups lie in the clefts on the surface of the molecule forming the structure of the hemoglobin.

Hemoglobin analysis reveals three different patterns of normal hemoglobin in an adult. These are Hb A (95 to 98%) containing two alpha and two beta chains, Hb A2 (2% to 3%) containing two alpha and two delta chains, and Hb F (less than 1%) containing two alpha and two gamma chains.

Hemoglobin C (Hb C), on the other hand, is one of the common structural variants of normal hemoglobin in which lysine is substituted for the glutamate in the sixth position of the beta-globin chain making it less soluble than Hb A. Hemoglobin C can either be in the homozygous states (Hb CC) or in the heterozygous states (Hb SC, Hb AC). Persons with hemoglobin C trait (Hb AC) are phenotypically normal and generally do not show any symptoms while persons with hemoglobin C disease (Hb CC) may present with mild chronic hemolysis, splenomegaly, and jaundice. Although hemoglobin C disease is a mild disease and does not develop into serious clinical complications, its inheritance with other hemoglobinopathies such as hemoglobin S (Hb SC) may have serious consequences. Thus, utmost care, treatment, and genetic counseling must be provided to these patients.