Acute erythremic myelosis (true erythroleukaemia): a variant of AML FAB-M6

Aims-Classic erythroleukaemia (acute myeloid leukaemia M6, or M6 AML) is de fined as an excess of myeloblasts in an erythroid predominant background. L eukaemia variants in which the primitive blast cells are demonstrably eryth roid are extremely rare and poorly characterised. Variably referred to as " true erythroleukaemia" or "acute erythremic myelosis", they are often inclu ded within the M6 AML category even though they do not meet strict criteria for this type of AML. Methods- Two cases of acute erythroid neoplasia are presented with clinical , morphological, immunophenotypic, and cytogenetic analysis. Results-Both patients presented with profound anaemia, one in a setting of long standing myelodysplasia. Bone marrow examination revealed a predominan t population of highly dysplastic erythroid cells in both cases. In one cas e, the liver was infiltrated by neoplastic erythroid cells. Both patients d ied within four months of diagnosis. Conclusions-This report illustrates that cases of acute leukaemia occur in which the dominant neoplastic cell is a primitive erythroid cell without an accompanying increase in myeloblasts. This does not preclude the neoplasti c clone originating in a multipotent haemopoietic stem cell, as suggested b y cases arising in patients with myelodysplasia. Acute erythremic myelosis should be recognised as a distinct variant of M6 AML.