CRLF2 and acute lymphoblastic leukemia: DS–ALL also has a higher proportion of rearrangements affecting the CRLF2 locus (~50% in DS–ALL vs 4–5% in non-DS–ALL), with interstitial deletion of the pseudoautosomal region PAR1 (that fuses CRLF2 to the first non-coding exon of P2RY8) or chromosomal translocation to the immunoglobulin heavy chain (IgH) locus [64–66].