Cardiac Registry screening for DiGeorge Critical Region deletion using loss of heterozygosity analysis

DiGeorge (DGS), velocardiofacial, and conotruncal anomaly face syndromes comprise a phenotypic spectrum that is associated with a submicroscopic 22q11.2 deletion in the majority of cases. These syndromes variably express complex congenital heart disease, cellular immune deficits, hypocalcemia, craniofacial anomalies, and learning disabilities. This retrospective study correlates the presence of a deletion in this region with autopsy and clinical findings in a cohort of patients selected from the Cardiac Registry at Boston Children's Hospital. DNA was extracted from formalin-fixed paraffin-embedded cardiac tissue sampled from 189 patients with conotruncal anomalies. Polymerase chain reaction (PCR) was performed using 4 fluorescently labeled oligonucleotide primer pairs for unique short tandem repeat polymorphisms in the DGS critical region. The PCR products were analyzed for loss of heterozygosity (LOH), and a deletion was assumed when at least 3 consecutive loci demonstrated homozygosity. Of the 189 cases, 16 (8%) met our criteria for LOH and were assumed to have a deletion. These patients included 6 (35%) of 17 patients diagnosed clinically with DGS prior to death. Of the 10 non-DGS patients with LOH, 4 had aortic atresia and 3 had tetralogy of Fallot, both frequently seen in DGS. Polymerase chain reaction is a useful screening alternative to fluorescence in situ hydridization for detecting 22q11.2 deletions in archived tissue samples. This study identified a probable deletion in a subset of cases from a cardiac registry with cardiac defects associated with the DGS phenotype.