Background Microdeletion of the BP1-BP2 region on chromosome 15q11.2 is one of the most commonly reported copy number variants (CNVs) in the clinical population. It has been suggested that this deletion may impact cognitive, behavioural, and neurological function, as it has been observed with a higher frequency in patients being investigated for neurodevelopmental disorders (NDDs) than in controls. Retrospective case reports suffer from ascertainment bias and provide limited information about specific neurobehavioural deficits.

Objectives Our study aims to collect detailed phenotypic data on proband and non-proband carriers of the 15q11.2 BP1-BP2 deletion, in particular the intellectual and behavioural profiles of these individuals.

Design/method Families with at least one member with 15q11.2 BP1–2 deletion were recruited from clinicians. Participants were examined by a clinical geneticist, and a structured medical and family history was obtained. Psychometric and behavioural testing protocol included standardised measures of intelligence, language ability, autistic symptomatology, attention, and mental health.

Results Results from the first eight participants are reported. Four participants fell within the Intellectually Disabled range (IQ <70). None of the participants met criteria for autism spectrum disorder. However, attention deficit-hyperactivity disorder (ADHD) was present in all children.

Conclusions Our preliminary data shows that individuals with 15q11.2 deletion may be more likely to have ADHD, mild intellectual disability and articulation difficulties. Further study of additional probands and non-proband carriers is ongoing.