Acute massive myelofibrosis with acute lymphoblastic leukemia.

Acute myelofibrosis is characterized by pancytopenia of sudden onset, megakaryocytic hyperplasia, extensive bone marrow fibrosis, and the absence of organomegaly. Acute myelofibrosis in patients with acute lymphoblastic leukemia is extremely rare. We report a 4-year-old boy who was diagnosed as having acute massive myelofibrosis and acute lymphoblastic leukemia. Performing bone marrow aspiration in this patient was difficult (a "dry tap"), and the diagnosis was established by means of a bone marrow biopsy and immunohistopathologic analysis. The prognostic significance of acute myelofibrosis in patients with acute lymphoblastic leukemia is not clear.