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The French-American-British (FAB) classification of acute myeloid leukaemia (AML) includes a category, M6 AML, in which there is an excess of myeloblasts in an erythroid dominant marrow. 1 The erythroblasts are often dysplastic and it is generally accepted that they are part of the neoplastic clone. The FAB classification does not include a category for cases where the neoplastic cells are immature erythroid cells without there being an excess of myeloblasts. However, such cases have been described by others and have been variously designated acute erythromyelosis, acute erythremia, acute erythremic myelosis, erythroblastic leukaemia, erythroleukaemia, Di Guglielmo's syndrome, Di Guglielmo's disease, M6 AML, or M6 AML "variant". 2 - 10 We report two additional cases of aggressive acute leukaemia in which the neoplastic cells were clearly erythroid, without an excess of myeloblasts. These two cases are true erythroid neoplasms that should be recognised as a subset of acute leukaemia, as has been proposed recently by the World Health Organisation's preliminary classification of acute leukaemia. 11
Case reports
CASE 1
This patient was noted at age 30 in 1977 to have asymptomatic macrocytic anaemia when he was rejected as a volunteer blood donor. At that time, the haemoglobin concentration (Hb) was 122 g/litre with a mean corpuscular volume (MCV) of 112 fl. White blood cell (WBC) and platelet counts were normal. He required no transfusion or other treatment for several years. Past medical history revealed bilateral undescended testicles and hypogonadism, for which he had been receiving testosterone supplements. In 1983, the patient also developed rheumatoid arthritis.
In 1988, dysplastic features (anisocytosis, poikilocytosis, tear drop poikilocytes, and occasional myelocytes and blasts) were noted in the peripheral blood. Bone marrow cytogenetic analysis was normal. In 1992, his anaemia became more severe and bone marrow examination showed trilineage dysplasia consistent with refractory anaemia. By February 1998, his Hb had fallen to 90 g/litre and a trial of erythropoietin treatment was begun. His Hb continued to fall and by August 1998 he had become transfusion dependent. Repeat bone marrow examination at that time showed refractory anaemia with no excess of blasts. However, two weeks later his platelet count, which had previously been normal, had dropped to 29 x 10 9 /litre. Hepatosplenomegaly developed together with an acute deterioration in liver...