Juvenile myelomonocytic leukemia (JMML) is a clonal hematopoietic disorder of early childhood characterized by excessive growth of monocytes and granulocytic cells. This disorder accounts for 2-3% of all childhood hematologic malignancies. Patients with JMML have a median age at diagnosis of 2 years (range 4 months – 6 years). Clinical features include pallor, fever, infection, skin bleeding and cough along with marked enlargement of spleen and liver as well as leukemic skin infiltrates. Peripheral blood smear shows elevated monocyte count and bone marrow with <30% blasts.
JMML is a rapidly fatal disorder for most children if left untreated. The median survival time without transplant is about 1 year.