Update on the clinical spectrum and genetics of red blood cell membrane disorders.

Disorders of the red blood cell membrane, such as hereditary spherocytosis, hereditary elliptocytosis, and hereditary pyropoikilocytosis, are characterized by heterogeneity in their clinical and laboratory manifestations. Advances in molecular biology have allowed determination of the precise genetic defect in many cases of membrane-associated anemia and have revealed significant genetic heterogeneity. Six genetic loci have been identified and many defects, including gene deletions and insertions, missense and nonsense mutations, and splicing mutations, have been found. Analysis of these defects has provided a better understanding of the pathogenesis of these disorders and allowed a better understanding of the structure/function relationships of the proteins of the erythrocyte membrane.