5q35 microduplication syndrome

5q35 microduplication syndrome (also known as NSD1 duplication syndrome or 5q35.2-q35.3 microduplication syndrome) is a rare chromosomal disorder caused by a microduplication of the 5q35 region, which includes the NSD1 gene. This condition is considered the reciprocal of Sotos syndrome, which is caused by deletions or loss-of-function mutations in the same region. In contrast to the overgrowth seen in Sotos syndrome, 5q35 microduplication syndrome is typically characterized by undergrowth, including short stature, microcephaly (small head size), and delayed bone age. The syndrome affects multiple body systems, particularly the skeletal, neurological, and craniofacial systems. Key clinical features include proportionate short stature, microcephaly, mild to moderate intellectual disability or learning difficulties, and delayed speech and motor development. Craniofacial features may include a small, narrow face and clinodactyly (curved fingers). Some patients may also exhibit feeding difficulties in infancy and behavioral issues. The severity of symptoms can vary considerably among affected individuals, even within the same family, likely depending on the size of the duplicated segment and other genetic modifiers. There is currently no specific cure or targeted therapy for 5q35 microduplication syndrome. Management is supportive and symptom-based, involving multidisciplinary care. This may include growth monitoring, developmental assessments, speech therapy, occupational therapy, educational support, and regular follow-up with pediatric specialists. Genetic counseling is recommended for affected families, as the duplication can be inherited from a mildly affected or apparently unaffected parent.

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