Using array-based Comparative Genomic Hybridization (aCGH) to screen 2,400 individuals with isolated or syndromic mental retardation for copy number variation, Giorda et al. (2009) identified 8 (0.33%) unrelated individuals, 2 males and 6 females, with a microduplication at chromosome<unk> .23-p11.22. The rearrangement was familial in 3 patients. A female patient shared a 4.5-Mb<unk>  with her affected mother and sister, and an unrelated male patient shared a 4.5-Mb<unk>  with his affected mother and sister. A third unrelated male inherited a smaller 0.8-Mb<unk>  from his unaffected mother. Three additional individuals had de novo 4.5-Mb<unk> s, and 2 more had partially overlapping de novo 6.0- and 9.2-Mb<unk> s. Paternal origin of the<unk>  was demonstrated in all de novo female cases. Six affected females had selective inactivation of the normal X chromosome, whereas 3 had random X inactivation. Breakpoints could be identified in 8 individuals. The recurrent<unk>  was flanked distally by a segmental<unk>  (D-REP at 47.8-48.2 Mb) containing a cluster of genes and pseudogenes of the synovial sarcoma X breakpoint (SSX) and proximally by a complex repeat (P-REP at 52.1-53.1 Mb) rich in SSX, melanoma antigen and X antigen (XAGE) genes. Sequence analysis of the junctions demonstrated that the recurrent 4.5-Mb<unk> s were mediated by non-allelic homologous recombination (NAHR) or Alu-mediated recombination. The majority of these recombinations occurred between flanking complex segmental<unk> s. Region of<unk>  and copy number variation can be further confirmed by Fluorescence In-Situ Hybridization (FISH) and PCR.
Xp11.2 duplication
Chromosome 2q deletion
2q37 monosomy
Chromosome 15q partial deletion
Partial monosomy 13q
Distal trisomy 10q
Tetrasomy 18p
Chromosome 15q trisomy