819 LEUKEMOID REACTION IN DOWN'S SYNDROME: IN VITRO MATURATION OF CIRCULATING STEM CELLS

Abstract

A marked increase in WBC count with blast cell predominance in blood is a well known hematological abnormality seen in neonates with Down's syndrome. Differentiation of true leukemia from a transient leukemoid reaction is often difficult. Examination of in vitro colony formation and maturation by circulating stem cells may be helpful in separating the two entities. We studied a newborn infant with trisomy 21 Down's syndrome who had juandice, 5 cm palpable liver and 1 cm palpable spleen. The Hb, WBC and platelet count at day 3 of life were 12.5 gm %, 62,300 with 58% blasts and 90.5×10³/mm³, respectively. Blood group incompatibility and intrauterine infections were excluded. The marrow showed 17% blasts. Prominent large basophilic granules were present in late myeloid precursors. The patient was simply observed. During the next 6 weeks the hematological picture returned to normal. Cultures of blood stem cells using the methylcellulose system were done on two occasions at day 9 of age (WBC 38.5×10³, 47% blasts), and at day 26 of age (WBC 17.7×10³, 6% blasts). The first blood formed 1,525 myeloid and 213 erythroid, and the second blood 256 myeloid and 17 erythroid colonies/ml of blood, respectively. No maturational difficiency was observed by cytological study of representative colonies. This normal maturation pattern is consistent with the spontaneous resolution of the clinical picture. The technique may be a useful tool in predicting the outcome.

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