Molecular characterization of patients with clinical suspicion of 22q11.2 deletion syndrome

Background 22q11.2 deletion syndrome (22q11.2 DS) is one of the most common genetic causes of learning disability. The aim of the study was to characterize genetically the individuals with clinical suspicion of 22q11.2 DS using sequential cytogenetic approach. Patients and methods The present study was conducted on 20 patients with features suggestive of 22q11.2 DS including cardiac, velopharyngeal, craniofacial, and other dysmorphic features. Cytogenetic and molecular analyses were performed by conventional karyotyping and fluorescence in-situ hybridization (FISH). Multiplex ligation-dependent probe amplification analysis (MLPA) was done for cases clinically suspected of being affected with 22q11.2 DS and showing no deletion by FISH. Results Conventional karyotyping revealed two (10%) cases and FISH analysis revealed four cases with deletion in the 22q11.2 region. No more cases were detected by MLPA analysis compared with FISH. Conclusion The diagnosis of 22q11.2 DS is primarily suspected by clinical picture. The cytogenetic diagnosis can be greatly improved by using FISH analysis, which detects the typical deletion in the 22q11.2 low copy repeats A–B, whereas atypical or distal deletion in 22q11.2 low copy repeats B–C, B–D, or C–D can be detected by MLPA analysis, which will allow more precise determination of the size and location of the deletion.