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 remis-sion. 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, chro-mosome analysis revealed constitutional mosaicism for trisomy 21. Supportive management was given with-out use of chemotherapeutic agents. Complete remission occurred within 2 months. Key words: transient leukemia, mosaic trisomy 21, congenital leukemia Leukemia is very rare in a neonate. If it does occur in a newborn, it is usually associated with trisomy 21. Thirty to fifty percent of these leukemias are transient. Al-though the clinical course is generally transient and be-nign, it may also be a preleukemic disorder and need regular follow up. Identification of transient leukemia (TL) and differentiating it from congenital leukemia ca