Transformation of congenital neutropenia into monosomy 7 and acute nonlymphoblastic leukemia in a child treated with granulocyte colony-stimulating factor.

A cytogenetically normal infant with Kostmann syndrome (severe congenital granulocytopenia) was treated with granulocyte colony-stimulating factor, which resulted in a rapid improvement in his neutrophil count and a resolution of recurrent infections. After 11 months of therapy, splenomegaly developed, with thrombocytopenia, anemia, circulating nucleated erythrocytes, and acquired monosomy 7, which evolved during a period of 7 months into acute nonlymphoblastic leukemia. The use of granulocyte colony-stimulating factor in patients with congenital marrow failure disorders may induce or hasten the onset of a malignant transformation.