Congenital dyserythropoietic anemias.

The congenital dyserythropoietic anemias (CDAs) are an uncommon and heterogeneous group of disorders characterized by markedly ineffective erythropoiesis and, usually, striking dysplastic changes in erythroblasts. Each of the three originally described forms, designated CDA types I to III, is defined by the presence of distinctive morphologic (including ultrastructural) abnormalities in erythroblasts. CDA type II is also characterized by a marked reduction in polylactosamine structures associated with the erythrocyte membrane glycoprotein, band 3 (detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis), and, usually, a positive result on the acidified serum lysis test. The course of CDA is often complicated by cholelithiasis. Even patients who have not had transfusions sometimes develop substantial iron overload. Recent studies have extended our knowledge on the clinical manifestations of CDA types I and III and have revealed the existence of forms of CDA distinct from types I to III. Information is now available on the chromosomal localization of the genes involved in CDA types I and II and in the Swedish cases of CDA type III. A few patients with CDA type I have been treated with interferon-alpha2, with a good response.