Identification of microdeletion and microduplication syndromes by chromosomal microarray in patients with intellectual disability with dysmorphism.

BACKGROUND: A retrospective analysis using chromosomal microarray in syndromic patients with intellectual disability from genetic clinics of a tertiary healthcare center in India was conducted.

AIM: To identify the spectrum of chromosomal abnormalities detected on microarray analysis.

SETTINGS AND DESIGN: Cases were identified among those with intellectual disability with dysmorphism attending genetic clinics of a tertiary care center.

PATIENTS AND METHODS: All patients attending genetic clinics over a 3-year period were analyzed. Clinical profile and baseline investigations were noted on a predesigned proforma. Among the 65 studied cases, there were 12 cases suggested to be having Prader-Willi syndrome (PWS), 27 cases with DiGeorge/velocardiofacial syndrome (DGS), and 1 case with Williams-Beuren syndrome (WBS). These were detected by fluorescent in situ hybridization (FISH) analysis with specific probes and were excluded from the final analysis. Chromosomal microarray analysis (CMA; single-nucleotide polymorphism-based array-comparative genomic hybridization) was performed as per the clinical indication in selected patients with dysmorphism, microcephaly, mental retardation, and/or multiple malformations. These patients had a negative result on FISH analysis.

RESULTS: In suspected patients with PWS, FISH and methylation testing confirmed six cases to be really PWS. FISH also detected five cases of DGS and one case of WBS. These were excluded from the final analysis. Among the 18 cases tested by CMA, in 13 patients, abnormalities with potential clinical significance were identified. Genetic counseling was done in all these cases. Prenatal diagnosis was done in one family.

CONCLUSION: In cases with dysmorphism with or without mental retardation or cardiac defect, advanced studies such as CMA can lead to a definitive diagnosis. Genetic counseling is mandatory in all these cases and a prenatal diagnosis is also feasible in selected families.