In this issue of Blood, Maloney et al report that the inferior outcome of ALL in children with DS is explained by the infrequency of the typical genetic subtypes characterizing common ALL. Children with Down syndrome (DS) have a markedly increased risk of both myeloid and lymphoblastic leukemias. Whereas the myeloid leukemias have unique clinical characteristics, the acute lymphoblastic leukemias (ALLs) of DS have a similar clinical appearance to the "common" B-cell precursor (BCP) ALLs seen in children without DS, with the notable absence of infant leukemias.3 The peak age is approximately 5 years. The immuno-phenotype is typical for BCP ALL, namely positive for CD 10, CD 19, and CD79a, and usually classified into the standard National Cancer Institute risk group. Yet, Maloney et al report that despite this phenotypic similarity, the spectrum of genetic anomalies in DS-ALL is markedly different from sporadic ALL (see figure).
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