Proximal 16p11.2 microdeletion syndrome

Proximal 16p11.2 microdeletion syndrome (also known as 16p11.2 deletion syndrome, BP4-BP5 deletion) is a chromosomal disorder caused by a recurrent deletion of approximately 600 kilobases (kb) on the short arm of chromosome 16 at the 16p11.2 region. This deletion encompasses roughly 25–30 genes and results in a clinically variable neurodevelopmental condition. The syndrome is one of the most common recurrent copy number variants associated with autism spectrum disorder (ASD), though not all individuals with the deletion meet criteria for ASD. The condition primarily affects the nervous system, leading to developmental delay, intellectual disability (often mild to moderate), speech and language delays, and behavioral difficulties including autism spectrum features, attention deficit hyperactivity disorder (ADHD), and anxiety. A hallmark physical feature is a predisposition to obesity, which typically becomes apparent in childhood and may be associated with increased appetite. Macrocephaly (large head size) is frequently observed. Seizures or epilepsy occur in a subset of affected individuals. Some patients may have minor dysmorphic facial features, vertebral anomalies, or other congenital malformations, though these are variable and often subtle. There is no cure for proximal 16p11.2 microdeletion syndrome, and management is supportive and symptom-based. Early intervention services including speech therapy, occupational therapy, behavioral therapy, and special education support are cornerstones of treatment. Weight management programs may be recommended to address obesity risk. Seizures are treated with standard antiepileptic medications. Regular developmental and neuropsychological assessments are important for optimizing outcomes. Genetic counseling is recommended for affected families, as the deletion may be inherited from a mildly affected or apparently unaffected parent, or may arise de novo.

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