Prevalence of 22q11 microdeletions in DiGeorge and velocardiofacial syndromes: implications for genetic counselling and prenatal diagnosis.

TLDR

Deletions of chromosome 22q11 are associated with DiGeorge syndrome and velocardiofacial syndrome. The study analyzed 76 patients with DGS or VCFS to determine the prevalence of 22q11 deletions. The authors used probes and cosmids from the DiGeorge critical region for DNA dosage analysis and fluorescence in situ hybridisation, and performed prenatal FISH testing in two pregnancies. They found 83 % of DGS and 68 % of VCFS patients had 22q11 deletions, rising to 88 % and 76 % when including prior cases, and concluded that FISH is an efficient, direct method for detecting these deletions in affected individuals and high‑risk pregnancies.

Abstract

Deletions of chromosome 22q11 have been seen in association with DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS). In the present study, we analysed samples from 76 patients referred with a diagnosis of either DGS or VCFS to determine the prevalence of 22q11 deletions in these disorders. Using probes and cosmids from the DiGeorge critical region (DGCR), deletions of 22q11 were detected in 83% of DGS and 68% of VCFS patients by DNA dosage analysis, fluorescence in situ hybridisation, or by both methods. Combined with our previously reported patients, deletions have been detected in 88% of DGS and 76% of VCFS patients. The results of prenatal testing for 22q11 deletions by FISH in two pregnancies are presented. We conclude that FISH is an efficient and direct method for the detection of 22q11 deletions in subjects with features of DGS and VCFS as well as in pregnancies at high risk for a deletion.