The performance of CGH array for the detection of cryptic constitutional chromosome imbalances

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Abstract
Ten cases with known cryptic aberrations were selected (seven cases with subtelomeric rearrangements, one case with an interstitial deletion and two cases with microdeletion syndromes: one case with DiGeorge syndrome and one case with a microdeletion of 17p11 (Smith Magenis syndrome) in 60% of the lymphocytes). The 10 cases contained altogether 16 aberrations, with sizes ranging from 1.3 to 20.5 Mb, and they were located on 15 different chromosome arms. Routine chromosome analysis (450–500 bands) had failed to detect the rearrangements in all cases. Cases 2–8 (table 1) were identified using subtelomeric FISH probes. Cases 3–6 and 8 were previously published.6, 33 Case 7, with an interstitial deletion of 15q24, was serendipitously detected during subtelomeric screening, as the 15q control probe (LSI PML) in the subtelomeric screening kit (Vysis Inc, Downers Grove, IL) was deleted. Cases 9 and 10 were detected using microdeletion FISH probes. Case 1 was identified by spectral karyotyping. Despite the large chromosome fragments involved in the unbalanced translocation in this case, repeated standard G-band analysis could not reveal this rearrangement due to the similarity in the banding pattern of the chromosome fragments involved. All chromosome imbalances were size mapped using BAC and PAC clones based on clone mapping databases (www.ensembl.org, July 2003), except for case 9, which was size mapped using a chromosome 22 specific micro-array.31

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