Background: Microdeletions within chromosome 15q13.3 are associated both with a recently recognised syndrome of mental retardation, seizures, and dysmorphic features, and with schizophrenia.
Methods and results: Based on routine diagnostic testing of ∼8200 samples using array comparative genomic hybridisation, we identified 20 individuals (14 children and six parents in 12 families) with microdeletions of 15q13.3. Phenotypes in the children included developmental delay, mental retardation, or borderline IQ in most and autistic spectrum disorder (6/14), speech delay, aggressiveness, attention deficit hyperactivity disorder, and other behavioural problems. Both parents were available in seven families, and the deletion was de novo in one, inherited from an apparently normal parent in four, and inherited from a parent with learning disability and bipolar disorder in two families. Of the 14 children, six in five families were adopted, and DNA was available for only one of these 10 biological parents; the deletion was very likely inherited for one of these families with two affected children. Among the unavailable parents, two mothers were described as having mental retardation, another mother as having “mental illness”, and one father as having schizophrenia. We hypothesise that some of the unavailable parents have the deletion.
Conclusions: The occurrence of increased adoption, frequent autism, bipolar disorder, and lack of penetrance are noteworthy findings in individuals with deletion 15q13.3. A high rate of adoption may be related to the presence of the deletion in biological parents. Unconfirmed histories of antisocial behaviours in unavailable biological parents raise the concern that future research may show that deletion 15q13.3 is associated with such behaviours.
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Funding: This work was supported by US National Institutes of Health grants HD-037283, M01-RR00188 (General Clinical Research Center), HD-024064 (Mental Retardation and Developmental Disabilities Research Center) and RR-019478 (Rare Disease Clinical Research Consortia) and by generous support from the William Stamps Farish Fund.
Competing interests: Many of the authors are faculty members in the Department of Molecular and Human Genetics at Baylor College of Medicine (BCM) which offers extensive genetic laboratory testing including use of arrays for genomic copy number analysis, and the department derives revenue from this activity.
Patient consent: All family specific information about social behaviour and all photographs of children and parents have been omitted from this article in order to minimise any potential for stigmatisation