Genetic disorders of human red blood cells.

Human red blood cells (RBCs) are subject to an enormous degree of genetic diversity. The variability that occurs may result in anemia, cyanosis, polycythemia, or may cause no hematologic alterations. Genetic abnormalities affecting hemoglobin include the sickling disorders, the unstable hemoglobinopathies, hemoglobinopathies associated with polycythemia or with methemoglobinemia, and the alpha- and beta-thalassemias. The most common enzymatic abnormality of RBCs is glucose-6-phosphate dehydrogenase deficiency, but defects of many other enzymes leading to hemolytic anemia have been identified. Deficiences of RBC enzymes may also be important in the diagnosis of nonhematologic disease and in the evaluation of dietary status.