Baseline characteristics of a nationwide cohort of pediatric patients with acute leukemias of Down syndrome.

Down syndrome (DS) or trisomy 21, brings together some unique aspects from clinical pediatrics. Among the hematological disorders present in DS, by far the most important is the predisposition for developing acute leukemia. Acute myeloid leukemia (AML) of DS has a preleukemic state with the onset in the neonatal period, rarely symptomatic but with the presence of blasts in peripheral blood smear and apparently a spontaneous remission. The unique tumor profile of DS underlines the importance of chromosome 21 in hematopoiesis and it can help understanding leukemogenesis in general. The purpose of this study was to present the very rare cases with DS and transient leukemia and/or acute leukemia that were found in a nationwide survey of Romania, in three centers of pediatric hematology and oncology. A nationwide analysis of the very rare cases of transient leukemia of DS are described, involving the three major pediatric hematology centers of Romania: Cluj Napoca, Bucharest and Timisoara. Data analysis was performed using R 3.5.3. Categorical variables were presented as absolute value (percent). Contingency tables were analyzed using the Fisher test. Normality of the distribution was assessed using the Shapiro test and histogram visualization, but also took into consideration the sample size. Non-normally distributed variables were presented as median (quartile 1, quartile 3). Wilcoxon test was used to determine the differences between two non-normally distributed groups. A p value under 0.05 was considered statistically significant. It appears that the more aggressive entity at presentation is represented by CD45 positive leukemia, which is the more frequent of the myeloid lineage and has lower counts at diagnosis. We address this manuscript to pediatricians and neonatologists in order to emphasize the importance of diagnosing hematological disorders in children with DS, especially neonates, even if they are asymptomatic.