This could be explained by the reported low frequency of CRLF2 pathogenic variants in pediatric cohorts, which is approximately 2% (Chen et al., 2012), and the higher co-occurrence (about 10%) between JAK2 variants and CRLF2-r in non-Down Syndrome ALL (Harvey et al., 2010b). This evidence concerns the gene CRLF2 and acute lymphoblastic leukemia.