Hematology Case Study - Hemoglobin C Disease

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This sample (pdf), from a patient with Hemoglobin C (Hb C) disease, shows anemia with marked anisocytosis per the RBC impedance histogram. Review of the smear confirms the automated results and shows target cells, poikilocytosis, Howell-Jolly bodies, and rare hemoglobin C crystals.

Hemoglobin C is one of the most common hemoglobin variants found in humans and may be responsible for causing anemia with mild hemolysis and splenomegaly. The structural abnormality of the ß-globin chain causes decreased solubility of the hemoglobin molecule, resulting in crystal formation and increased cellular rigidity which, in turn, leads to shortened red cell survival. A person may be heterozygous for Hb C, in which case they are considered to have hemoglobin C trait and are usually asymptomatic; hemoglobin C disease is diagnosed in patients whom are homozygous. Hb C is closely related to hemoglobin S which is responsible for sickle cell disease. Both hemoglobin variants are most common in people whose ancestors inhabited the world’s malaria zones and both have been found to have some degree of malaria resistance.

Certain abnormal hemoglobins such as Hb C, Hb S, and the combined form, Hb S-C, are known to produce hyper-dense RBCs with increased MCHC values due to altered surface volume and/or deformability of the RBCs.

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