Objective: Chromosomal duplications present diverse clinical manifestations depending on the duplicated region. While full trisomies (13, 18, 21) are well-characterized, rare forms like mosaic trisomy 8, partial trisomy 15q, and partial trisomy 17p remain less defined. This study characterizes their clinical and molecular spectrum to improve diagnostic accuracy and genetic counseling.

Materials and Methods: This retrospective study evaluated four patients admitted to Pamukkale University Medical Genetics, between 2020 and 2025 with suspected chromosomal anomalies. Ethical approval was obtained from the University Non-Interventional Clinical Research Ethics Committee. Patients underwent comprehensive genetic analysis including G-banded karyotyping, fluorescence in situ hybridization (FISH), and chromosomal microarray analysis (CMA). Clinical data were retrieved from medical records and analyzed alongside cytogenetic findings.

Results: The study cohort consisted of four female patients. Cytogenetic analysis identified mosaic trisomy 8 in two patients (mosaicism rates 48% and 54%), partial trisomy 15q secondary to an unbalanced translocation in one patient, and partial trisomy 17p in one patient. Common clinical features included hypotonia (100%), developmental delay (75%), and craniofacial dysmorphism (100%). Novel findings such as leukocoria were observed in mosaic trisomy 8 cases. CMA successfully refined breakpoints in microduplication syndromes where karyotyping was insufficient.

Conclusion: Rare chromosomal duplications exhibit significant clinical heterogeneity. This study underscores the necessity of integrating conventional karyotyping with high-resolution techniques like CMA for precise diagnosis. Our findings expand the known phenotypic spectrum of these syndromes and highlight the critical role of multidisciplinary management and family-based genetic counseling in improving patient outcomes.