Chromosomal rearrangements reported in individuals with OCD suggest that gene dosage effects could contribute to the determinism of the disorder. To our knowledge, this is the first study to systematically explore CNVs in OCD. As a preliminary study, we screened a sample of OCD patients for CNVs in the 15q11-13 and the 22q11.2 chromosomal regions. These two regions were chosen because patients with 22q11.2 deletion syndrome or PWS have an elevated incidence of obsessive-compulsive symptoms [12,18,20]. We did not detect any microrearrangement in these regions in our sample. If present, the prevalence of these chromosomal anomalies in OCD would be rare, i.e. under 2 × 10-3 (<1/472 chromosomes screened). MLPA is a highly reliable method to detect microrearrangements in the 15q11-q13 and 22q11.2 regions, and has been used with success by our group and others to screen subjects with autism spectrum disorders and mental retardation [22,23,27-29]. Thus, the negative findings in the present OCD sample cannot be ascribed to lack of sensitivity of the method to detect copy number abnormalities.
