Acute nonlymphocytic leukemia after transient myeloproliferative disorder in a patient with Down syndrome

An infant with Down syndrome (DS) and RH isoimmunization developed transient myeloproliferative disorder (TMD) during the neonatal period. At 16 months she presented with acute nonlymphocytic leukemia (ANLL). Cytogenetic studies during TMD showed trisomy 21 only but new abnormalities emerged during ANLL. She is now in complete remission 5 years after diagnosis. Patients with TMD have either trisomy 21 or mosaic 21 in blood and bone marrow but in phenotypically normal children this cell line disappears with resolution of the TMD. A review of the literature indicates that there are no clinical, hematological, or cytogenetic differences between DS children with TMD who subsequently develop acute leukemia and those who do not. However, the leukemia in the former group may differ in presentation, type, and possibly survival time from other DS children who develop leukemia de novo.