[Acute myelo-monocytic leukemia with collagenous medullary fibrosis and osteosclerotic lesions].

A case of acute myelo-monocytic leukemia (M4) in a 75 year old man with multiple osteosclerotic lesions is reported. Bone metastases were clinically and radiologically suspected. A surgical bone marrow biopsy at the iliac crest revealed a massive infiltrate of blasts with medullary fibrosis, large areas of osteosclerosis and foci of necrosis. Osteosclerosis is rarely observed during acute leukemias in adults. Differential diagnosis with acute myelofibrosis is discussed.