Hemoglobin C (abbreviated as Hb C or HbC) is an abnormal hemoglobin with substitution of a lysine residue for glutamic acid residue at the 6th position of the β-globin chain. This mutated form reduces the normal plasticity of host erythrocytes causing a hemoglobinopathy. In those who are heterozygous for the mutation, about 28–44% of total hemoglobin (Hb) is HbC, and no anemia develops. In homozygotes, nearly all Hb is in the HbC form, resulting in moderate normocytic hemolytic anemia. Target cells, microspherocytes and HbC crystals are found in a blood smear from a homozygous patient. Individuals heterozygous for both HbC and Hb S (Hb SC disease) or for HbC and thalassemia are known, and have atypical hemolytic anemias; sickling is enhanced in Hb SC disease. Hemoglobin C is found predominantly in West Africa and has been shown to protect against severe malaria.

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