Detection of 22q11.2 microdeletions by SemiQuantitaive MultiplexPCR (SQMPCR)

22q11.2 chromosomal region is a hot spot for many cytogenetic rearrangements especially microdeletions which are responsible for DiGeorge and VeloCardioFacial syndromes. The most characteristic sign in these patients is congenital cardiac conotruncal anomalies. The gold standard diagnostic test for these microdeletions is FISH (Fluorescent In Situ Hybridization). However this diagnostic technique has some drawbacks such as high final cost and low sensitivity in smaller and uncommon microdeletions found in this region. The aim of this study was to introduce a less expensive and a priori more sensitive molecular method to help small and peripheral laboratories to find genetic causes of congenital heart diseases and DiGeorge syndrome. 10 patients with congenital conotruncal anomalies and symptoms of DiGeorge syndrome were included in this study. These patients had been analyzed by FISH probe TUPLE1 before the inclusion. 3 normal persons were included as normal controls for microdeletion region. Semi Quantitative Multiplex PCRs were designed based on known markers in and out of the region of intrest. Results were analyzed by TotalLab software. 4 patients showed a decrease in gene dosage more than 60% compared to normal persons. FISH analysis found only one patient with microdeletion. The designed method based on semi quantitative PCR was able to find 4 patients (40%) with microdeletion in a population of 10 patients with congenital cardiac anomalies. This technique was also able to find microdeletions in three FISH negative patients. Molecular diagnosis of microdeletions is supposed to be more sensitive than FISH in small microdeletions. This study confirms the presence of atypical deletions in Iranian patients and shows that the applied technique can detect some FISH negative patients. However further studies are needed to determine the sensitivity and specificity of the mentioned molecular diagnosis. It seems that this can be used at least for the patients with typical phenotypic features of 22q11DS and negative FISH results.