Among high-risk cases, infant leukemias (those diagnosed at age < 1 year) are a special subgroup with distinctive clinical and biological features, including frequent MLL (Mixed Lineage Leukemia, also known as KMT2A) rearrangements, high FLT3 (FMS-like tyrosine kinase 3) expression and high sensitivity to the nucleoside analogue cytarabine (Ara-C), but a dismal prognosis [1–6]. The gene discussed is FLT3; the disease is leukemia.