Schematic representation of the cryptic insertion of 11q23 sequences in Xq26.3. The 11q23 breaks occurred 2,931 bp downstream of the FXYD2 gene and 89 bp upstream of MLL exon 10, respectively (A). A large fragment of 653,099 bp from chromosome 11q23 was inserted in Xq26.3 (B), leading to the transfer to Xq26.3 not only of the 5' MLL region (exons 1 to 9) but also of 16 other genes (FXYD6, TMPRSS13, IL10RA, APOO2962.2, TMPRSS4, SCN4B, SCN2B, AMICA1, MPZL3, MPZL2, CD3E, CD3D, CD3G, UBE4A, ATP5L, and AP001267.2). The insertion resulted in the disruption of the DDX26B gene (550 bp downstream of DDX26B exon 8) and placed the 5' MLL region 3,951 bp upstream of the CT45A2 gene. As a result of the insertion, the CT45A1 gene was also deleted.