Chromosome 22q11 deletions - An under-recognised cause of idiopathic learning disability

Background Velo-cardio-facial syndrome (VCFS), a syndrome of multiple congenital abnormalities including characteristic dysmorphology, congenital heart defects and learning disability is associated with small interstitial deletions of chromosome 22q22. We tested the hypothesis that VCFS may be significantly under-diagnosed by screening a learning-disabled population for chromosome 22q11 deletions. Method Two hundred and sixty-five people with learning disability residing in two learning disability hospitals in South Wales were reviewed. They were selected for inclusion in the study if they fulfilled any of the following criteria: psychotic disorder (schizophrenia or affective disorder), family history of psychotic disorder, cleft palate and/or lip, congenital heart disease, broadly defined facial dysmorphism or a history of hypocalcaemia. Fluorescence in situ hybridisation studies were performed on 74 selected individuals. Results Cytogenetic analysis revealed that two people demonstrated a previously undetected chromosome 22q11 deletion. A third person demonstrated a previously undetected cytogenetically visible deletion on chromosome 15. Conclusions VCFS appears to be aetiologically significant in a proportion of individuals with idiopathic learning disability especially in those where psychosis is associated with mild learning disability. We suggest that clinicians should consider a chromosome 22q11 deletion in people who meet selection criteria.