A 13 year old girl with the typical clinical and haematological picture of congenital dyserythropoietic anaemia (CDA) is reported. The bone marrow is highly cellular with 70 per cent erythroid cells, and 28% bi- and multinuclear cells among the orthochromatic and polychromatic erythroblasts. Moderate megaloblastoid changes are present. On light microscopy the findings are in agreement with those described in CDA type II. On electron microscopy both the cytoplasmatic changes described as typical of CDA type II, and the nuclear changes found in type I can be demonstrated. The acidified serum test (Ham test) is negative with normal sera. The patient's red blood cells show increased agglutinability with anti-I and and anti-I antibodies, but no haemolysis. Total serum lipids are about 50% of the normal average. All lipoprotein classes are lowered to about the same extent. The total phospholipid content of the erythrocytes is slightly reduced, with a moderate, relative increase of the lecithin fraction and a decrease of the sphingomyelin fraction. Doubts can be raised about the tenability of the current classification of CDA based on morphological and serological criteria, especially about the distinction between types I and II.

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