A case of atypical congenital dyserythropoietic anemia (CDA). (A) May-Grünwald-Giemsa (MGG)-stained blood film of patient at 4 years of age after blood transfusion. N, nucleated red blood cell; P, poikilocyte; F, fragmented cell; T, target cell; S, spherocyte. No pretransfusion film was available. (B) MGG-stained marrow biopsy at 1 week of age. More than 90% of the cells are erythroid. There are a few multinucleated cells that are characteristic of certain forms of CDA. (C-E) Electron microscopy of bone marrow. (C) Low-power view of a cluster of erythroid cells. The cell membranes are ruffled and there is some degree of dyserythropoiesis, but hyperploidy is not marked. (D) An erythroblast with a “Swiss cheese” pattern of nuclear chromatin. (E) An erythroblast with prominent gaps in the nuclear membrane.