Hypocellular acute myeloid leukaemia-A diagnostic conundrum

Hypocellular acute leukaemia is a rare entity with an incidence of 5-12% of all acute leukaemias. Almost all reported cases are of myeloid lineage. It is defined by bone marrow hypocellularity (less than 20% of cellularity in trephine biopsy) with increase of bone marrow blasts (20% or more) and peripheral blood blastopenia. It is termed as a secondary disease in a pre-existing haematologic disorder or prior cytotoxic or radiation therapy and is often misdiagnosed as Myelodysplastic Syndrome (MDS). In this report, we describe an unusual case of Hypocellular Acute Myeloid Leukaemia (H-AML) without any past haematologic disease or radio/chemotherapy in an elderly male. The diagnosis of H-AML can be difficult and may be confused with Hypocellular MDS (H-MDS) and Aplastic Anaemia (AA). Presence of dysplasia and abnormal localization of immature precursors may not be able to differentiate between H-AML from H-MDS. Strict diagnostic criteria must be followed to arrive at correct diagnosis which includes counting atleast 100 leukocytes on peripheral smear and 500 leukocytes in Bone Marrow Aspirate (BMA).