Acute myelomonocytic leukemia (AMML) is a subtype of acute myeloid leukemia (AML) marked by differentiation toward both granulocytic and monocytic cell lines. AML is more common than acute lymphocytic leukemia (ALL) in neonates and infants, and AMML is the second most common subtype of AML seen in this population, accounting for approximately 17% of reported cases. Most cases of congenital and infant leukemia are thought to be secondary to chromosomal aberrations acquired in utero.

The presenting sign is of leukemia cutis in about half of patients, with leukemia cutis preceding other signs of leukemia by as long as 4 months. Patients with AML also show a high leukocyte count, hepatosplenomegaly, and a high likelihood for central nervous system (CNS) involvement. With leukemias that present later in infancy, signs and symptoms are often less specific and can include low-grade fever, pallor, lethargy, hepatosplenomegaly, bleeding diathesis, diarrhea, and failure to thrive. CNS involvement and male sex are independent adverse prognostic factors. The prognosis of neonatal / infant AML is generally bleak with or without chemotherapy; the overall survival is only 25% at 3 years.