NRXN1 deletion syndrome; phenotypic and penetrance data from 34 families.

The spectrum of phenotypes associated with heterozygous deletions of neurexin-1 (NRXN1) is diverse and includes: autism spectrum disorder, attention deficit hyperactivity disorder, intellectual disability, seizures, schizophrenia, mood disorders and congenital malformations. Reduced penetrance and variable expressivity of deletions in this gene remain a challenge for genetic counselling. We clinically reviewed 67 NRXN1 deletions from 34 families to document the phenotype and determine odds ratio. Thirty-four probands (5 adults, 29 children (<16 years)) were initially identified from a cohort clinically referred for arrayCGH. A further 33 NRXN1 deletions (16 with established phenotype) from the families were identified following cascade screening. Speech and language delay was a consistent clinical presentation. Pedigree analysis of the inherited group revealed numerous untested relatives with a history of mental health and developmental issues, most notably in the NRXN1β isoform patients. Our study highlights the complex nature of the NRXN1 phenotype in this population.