Transient Leukemia in a Case of Mosaic Trisomy 21

The incidence of leukemia in Down syndrome is 10 to 20 folds higher than that in the general population. If the leukemia occurs in a newborn, 30% to 50% are transient leukemia and will spontaneously go into remission. We describe here a female neonate who presented with an elevated white blood cell counts, associated with a high percentage of blast cells. A cytochemical stain of the bone marrow revealed properties of acute myeloblastic leukemia , which is rare in childhood. Although the baby had a nearly normal phenotype, chromosome analysis revealed constitutional mosaicism for trisomy 21. Supportive management was given without use of chemotherapeutic agents. Complete remission occurred within 2 months.