Distal 17p13.3 microdeletion syndrome

Distal 17p13.3 microdeletion syndrome (also known as isolated lissencephaly sequence when involving specific genes, or sometimes referred to as distal 17p deletion syndrome) is a rare chromosomal disorder caused by a small deletion at the distal end of the short arm of chromosome 17, in the 17p13.3 region. This region is distinct from the Miller-Dieker syndrome critical region, though there is overlap. The deletion typically involves the YWHAE gene and may include other neighboring genes, but critically does not extend to include the PAFAH1B1 (LIS1) gene, which distinguishes it from Miller-Dieker syndrome. When the PAFAH1B1 gene is not deleted, the severe lissencephaly characteristic of Miller-Dieker syndrome is typically absent. Clinical features of distal 17p13.3 microdeletion syndrome include mild to moderate intellectual disability, learning difficulties, speech and language delay, and behavioral problems such as autism spectrum features. Affected individuals may also present with mild facial dysmorphisms including a prominent forehead, midface hypoplasia, and subtle craniofacial asymmetry. Growth retardation, postnatal short stature, and mild structural brain anomalies (such as mild gyral abnormalities or corpus callosum anomalies) have been reported in some patients. Seizures may occur but are less common and less severe than in Miller-Dieker syndrome. There is currently no cure or specific targeted therapy for distal 17p13.3 microdeletion syndrome. Management is supportive and symptom-based, including early intervention programs, speech therapy, occupational therapy, behavioral support, and educational accommodations. Seizures, if present, are managed with standard antiepileptic medications. Regular developmental and neurological follow-up is recommended. Genetic counseling is important for affected families to understand recurrence risks.

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