The 22q11 PRODH/DGCR6 deletion is frequent in hyperprolinemic subjects but is not a strong risk factor for ASD

The proline dehydrogenase (PRODH) gene maps to 22q11.2 in the region deleted in the velo-cardio-facial syndrome (VCFS). A moderate to severe reduction (>50%) in PRODH activity resulting from recessive deletions and/or missense mutations has been shown to cause type 1 hyperprolinemia (HPI). Autistic features have been reported as a common clinical manifestation of HPI. Here we studied the frequency of a recurrent small 22q11.2 deletion encompassing PRODH and the neighboring DGCR6 gene in three case-control studies, one comprising HPI patients (n = 83), and the other two comprising autism spectrum disorder (ASD) patients (total of n = 2800), analyzed with high-resolution microarrays. We found that the PRODH deletion is a strong risk factor for HPI (OR = 50.7; 95%CI = 7.5-2147) but not for ASD (P = 0.4, OR = 0.6-3.3). This result indicates either that the suggested association between ASD and HPI is spurious and results from a bias leading to the preferential inclusion of patients with autistic features in HPI series, or that HPI is present in only a very small subset of ASD patients. In this latter case, a very large sample size would be required to detect an association between the PRODH deletion and ASD in a case-control study.