Early Erythroblastic Leukemia Presenting as De Novo Acute Leukemia.

Early erythroblastic leukemia is a newly defined type of leukemia in which the blasts have the same characteristics as erythroid precursors at the level of CFU-E. The blasts are characterized by the presence of carbonic anhydrase I, CD 36 antigen, platelet peroxidase (PPO)-like activity, and ferritin-containing granules. Early erythroblastic leukemia appears to have characteristic clinical features; in the original report of nine cases, only one patient had typical de novo acute leukemia. We report here a case of early erythroblastic leukemia that presented! as de novo acute leukemia. The blasts from this patient had almost the same ultrastructural and phenotypical characteristics as those of the originally reported cases, even though our case was not examined for anti-carbonic anhydrase I antibodies. As a single marker, PPOl activity can no longer be considered specific for the megakaryocyte-platelet lineage, even though the significance of transient expression of PPO-like activity in immature erythroblastic cells at the level of CFU-E still remains to be clarified. When leukemic blasts show positivity for CD36 and negativity for megakaryocytic or monocytic markers, the diagnosis of early erythroblastic leukemia should be suspected and electron microscopical characteristics should be studied.