A cancer-predisposing syndrome is always there: a sequential occurrence of acute lymphoblastic leukemia after acute myeloid leukemia in a child with down syndrome.

INTRODUCTION: Down syndrome (DS) is the most common cancer predisposing syndrome (CPS) associated with a markedly increased risk of pediatric hematologic malignancies, specifically acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Although both AML and ALL occur more frequently in children with DS than in the general pediatric population, the sequential development of both malignancies in the same patient is extremely rare.

RESULTS: Here we report the case of a child with DS who initially developed an AML and subsequentially an ALL, while the myeloid leukemia was in remission.

DISCUSSION: This case underscores the rarity of sequential AML and ALL in DS patients and supports the hypothesis that these leukemias represent biologically distinct diseases. Trisomy 21 has a central role in predisposing to both myeloid and lymphoid leukemogenesis through profound alterations of hematopoiesis and gene deregulation.