P25 Becker naevus is associated with neurocognitive abnormalities in a substantial proportion of children

Abstract

Abstract Becker naevus and Becker naevus syndrome are mosaic disorders caused in 60% of cases by postzygotic variants in the gene ACTB which encodes β-actin. We observed several patients with Becker naevus and coexistent neurocognitive abnormalities and began to study this potential association. All 51 patients seen in the last 5 years with a differential diagnosis of Becker naevus in electronic and/or photographic records were identified retrospectively. Clinical notes, photographs, radiology and histopathology were reviewed. Twenty-one patients were removed due to a different or doubtful final cutaneous diagnosis. Neurocognitive diagnoses were included only when made by a clinician, all external to the Paediatric Dermatology department. All but three patients had had their neurodevelopment assessed. Nine of the 27 patients assessed (33.3%) had a neurocognitive diagnosis, and all nine were male. Two children had autistic spectrum disorder (ASD), four had attention deficit hyperactivity disorder (ADHD) and two children had both diagnoses. MRI scans had been performed in six of the nine patients, and two had abnormal findings. A very substantial proportion of this cohort of patients with a definite diagnosis of Becker naevus have an independent diagnosis of ASD or ADHD, which in line with all-cause ASD/ADHD appears to be commoner in males. This is a new description. Germline genetic disorders caused by gain- or loss-of-function variants in ACTB are associated with neurocognitive abnormalities. Genotyping is ongoing to examine any association between the neurocognitive phenotype and mosaic ACTB variants in this clinical cohort.