ACUTE-LEUKEMIA AND THE TRANSIENT MYELOPROLIFERATIVE DISORDER ASSOCIATED WITH DOWN-SYNDROME - MORPHOLOGIC, IMMUNOPHENOTYPIC AND CYTOGENETIC MANIFESTATIONS

Individuals with Down syndrome have an increased incidence of leukemia compared to the general population. In addition, Down syndrome childr en may acquire a myeloproliferation that resembles acute leukemia that undergoes a spontaneous, durable remission. To clarify the relationsh ip between these two disorders, the morphologic, immunophenotypic and cytogenetic characteristics of 28 patients with Down syndrome and the morphologic manifestations of acute leukemia were examined. Three cyto morphological groups were discerned. The first two groups consisted of five patients with acute lympho blastic leukemia (group I) and three patients with acute myeloid leukemia (group II). These leukemias resem bled those of non-Down individuals. The third and largest group (group III) consisted of 20 cases of acute myeloid leukemia that showed prom inent megakaryocytic and/or erythroid differentiation and occurred in children under 6 years of age. The blasts in this group were non-react ive for myeloperoxidase or non-specific esterase and expressed CD7, CD 34 and CD36 with variable expression of CD61, CD13 and CD33. Four pati ents in this group had an acquired trisomy 8. Four group III leukemias underwent a durable, spontaneous remission within 2 months of diagnos is. There were no morphologic differences between those leukemias in t his group that progressed and those that remitted; however, all remiss ions occurred in newborns. It is concluded that Down syndrome children acquire a characteristic acute myeloid leukemia that has prominent me gakaryocytic and/or erythroid differentiation and an unusual immunophe notype. This group of leukemias may undergo a durable, spontaneous rem ission in the newborn period.