Clinically detectable copy number variations in a Canadian catchment population of schizophrenia

Copy number variation (CNV) is a highly topical area of research in schizophrenia, but the clinical relevance is uncertain and the translation to clinical practice is under-studied. There is a paucity of research involving truly community-based samples of schizophrenia and widely available laboratory techniques. Our objective was to determine the prevalence of clinically detectable CNVs in a community sample of schizophrenia, while mimicking typical clinical practice conditions. We used a brief clinical screening protocol for developmental features in adults with schizophrenia for identifying individuals with 22q11.2 deletions and karyotypically detectable chromosomal anomalies in 204 consecutive patients with schizophrenia from a single Canadian catchment area. Twenty-seven (13.2%) subjects met clinical criteria for a possible syndrome, and 26 of these individuals received clinical genetic testing. Five of these, representing 2.5% of the total sample (95% CI: 0.3%-4.6%), including two of ten patients with mental retardation, had clinically detectable anomalies: two 22q11.2 deletions (1.0%), one 47, XYY, and two other novel CNVs--an 8p23.3-p23.1 deletion and a de novo 19p13.3-p13.2 duplication. The results support the utility of screening and genetic testing to identify genetic syndromes in adults with schizophrenia in clinical practice. Identifying large, rare CNVs (particularly 22q11.2 deletions) can lead to significant changes in management, follow-up, and genetic counselling that are helpful to the patient, family, and clinicians.