“…The chromosome region 22q11.2 has long been recognized as a hotspot for genomic rearrangement and related disorders, such as 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome, OMIM 188400/ OMIM 192430) [DiGeorge and Harley, 1965;Shprintzen et al, 1978], der (22) t(11; 22) syndrome (OMIM 609029) and cat-eye syndrome (OMIM 115470) [Guanti, 1981;Edelmann et al, 1999a]. Der (22) syndrome and cat-eye syndrome are rare conditions characterized by increased copy-number of the most centromeric part of 22q11 [Zackai and Emanuel, 1980;McDermid and Morrow, 2002], whereas the microdeletions of 22q11.2 occur more often, with an estimated frequency of 1 in 4,000-6,000 live births [Yamagishi, 2002;Botto et al, 2003].…”