Microduplication

Microduplication is the duplication of a small segment of the genome, creating an extra copy of genetic material at a specific location. It is a subset of copy number variation (CNV). Because the duplicated region is often too small for conventional karyotyping, microduplications are typically detected by chromosomal microarray analysis or sequencing-based methods rather than standard cytogenetics. Duplicated segments commonly range from a few kilobases to several hundred kilobases, and the genes involved influence potential effects on phenotype.

Microduplications can be inherited from a parent or arise de novo, and they may be mosaic in some cases. They can alter gene dosage or disrupt regulatory elements, contributing to a spectrum of clinical outcomes from no apparent effect to neurodevelopmental disorders, congenital anomalies, or other features.

Interpretation is variable. Classification follows guidelines that label findings as pathogenic, likely pathogenic, variant of uncertain significance, likely benign, or benign. Correlation with clinical information, family data, and the exact gene content is important for counseling and management.

Some well-studied loci include 16p11.2 and 15q11.2 (BP1-BP2), where duplications have been associated with neurodevelopmental phenotypes in some individuals, though many carriers are asymptomatic. Management is individualized and may involve developmental assessment, medical surveillance, and genetic counseling regarding recurrence risk.