In fact, deregulation of the CRLF2 gene, either through deletions of Xp22.33/Yp11.32 or by translocations between these regions and the immunoglobulin heavy chain locus (IGH@) at 14q32.33, both undetectable by conventional chromosome banding analysis, is substantially more common in DS-ALL than in non-DS-ALL [17,18]. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.