A rare subtype of acute myeloid leukaemia with recurrent cytogenetic abnormalities characterised by clonal proliferation of myeloid blasts with predominantly megakaryoblastic differentiation in the bone marrow and blood, often with extensive infiltration of the abdominal organs. It occurs typically in infants and usually presents with hepatosplenomegaly, anaemia, thrombocytopenia and nonspecific symptoms related to ineffective haematopoesis (fatigue, bleeding and bruising, recurrent infections). Myelofibrosis and fibrosis of other infiltrated organs is also characteristic of this disease. [from SNOMEDCT_US]