Acute monoblastic leukemia with osteosclerosis and extensive myelofibrosis.

A 4-month-old infant was admitted with a monoblastic infiltration of the skin associated with osteosclerosis. Both lesions spontaneously disappeared within a few months, but 2 years later, a monoblastic leukemia occurred that was associated with marked skin erythema and myelofibrosis. Skin and bone marrow specimens showed a monoblastic infiltration with numerous intermingled mast cells of normal appearance. Whether myelofibrosis was a feature of a systemic mastocytosis or of the leukemic process is discussed in this case.