Detection of a subtle rearrangement of chromosome 22 using molecular techniques

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Abstract
Conventional cytogenetics is a useful clinical tool that has a lower limit of sensitivity of 2–5 Mb for detection of duplications of deletions. Because the threshold of clinically significant aneusomy is below this range, there is a need for approaches to improve the sensitivity of the detection of aneusomy. We have implemented a system of screening for subtle unbalanced translocations in children with multiple congenital anomalies of unkonwn cause. Our approach uses subtelomeric microsatellite markers to detect small areas of segmental aneusomy due to unbalanced translocations. Herein we report a patient with severe multiple congenital anomalies and a normal karyotype who was diagnosed by this approach. Microsatellite markers from 41 telomeres were analyzed and were normal with the exception of those on distal chromosome 22. Further analysis with additional microsatellites and fluorescent in in situ hybridization confirmed duplication of 22q13.2‐qter. We conclude that microsatellite screening can detect subtle unbalanced translocations in children with severe anomalies.