Distal 16p11.2 microdeletion syndrome

Distal 16p11.2 microdeletion syndrome (also known as 16p11.2 distal microdeletion syndrome) is a rare chromosomal disorder caused by a recurrent deletion of approximately 220 kilobases in the distal region of chromosome 16p11.2, a region distinct from the more commonly described proximal 16p11.2 microdeletion. This genomic region encompasses the SH2B1 gene, which plays an important role in leptin and insulin signaling, as well as several other genes. The deletion is typically around 200-600 kb and is identified through chromosomal microarray analysis. The syndrome primarily affects neurodevelopment and metabolism. Key clinical features include early-onset obesity, which is often severe and begins in childhood, developmental delay, intellectual disability of variable severity, and behavioral difficulties including features of autism spectrum disorder. Affected individuals may also exhibit dysmorphic facial features, though these are often subtle and nonspecific. Hyperphagia (excessive appetite) is a prominent feature linked to the loss of SH2B1. Additional findings may include seizures, speech and language delays, and learning difficulties. There is no specific cure for distal 16p11.2 microdeletion syndrome. Management is supportive and multidisciplinary, focusing on early intervention services including speech therapy, occupational therapy, and behavioral support. Obesity management through dietary counseling, exercise programs, and close metabolic monitoring is a critical component of care. Seizures, if present, are managed with standard antiepileptic medications. Regular developmental assessments and educational support are recommended to optimize outcomes. Genetic counseling is important for affected families, as the deletion may be inherited from a parent or occur de novo.

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