Despite their heterogeneity, the main clinical characteristics of patients with PWS or 22q11.2 deletion syndrome are relatively well recognized by psychiatrists. The non inclusion of patients with clear dysmorphic features in our study could explain at least in part why we were unable to detect any subjects with such deletions. However, patients with atypical or minimal phenotype (i.e., patients without the congenital heart defects, palate anomalies and distinctive facial features of the 22q11 deletion syndrome or without the characteristic obesity of PWS), would not have been recognized by the psychiatrists and in principle could have been included in the OCD sample. The fact that patients with significant mental retardation were absent from our sample also contributes to explain why we did not identify any subjects with 15q11-q13 or 22q11 microdeletions. Indeed, recent findings have shown that pathogenic CNVs are more frequent among individuals with moderate to severe intellectual disability [30].
