Copy Number Variations in a Turkish Cohort of Children with Intellectual Disability*

Objective: Intellectual disability (ID) is a complex, variable, and clinically heterogeneous neurodevelopmental disorder that affects 1% – 3% of the global population. Copy number variations (CNVs) contribute to approximately 15%–20% of ID cases. Array comparative genomic hybridization (aCGH) is the first-line test for diagnosing patients with ID with/without multiple congenital anomalies (MCAs). This study aimed to present CNVs identified in a retrospective aCGH cohort of Turkish patients with ID with/without other medical conditions. Materials and Methods: The study population consisted of 210 patients (139 male, 71 female) aged 2–18 years. aCGH analysis was performed using oligo and bacterial artificial chromosome (BAC)-based microarray platforms. CNVs were interpreted using public databases and literature mining and categorized according to international guidelines. Results: Forty-five CNVs were detected in 38 (18%) patients. Among these CNVs, 21 (46.6%) were pathogenic, 4 (8.8%) were likely pathogenic, and 8 (17.7%) were variants of uncertain clinical significance (VUS). Nineteen CNVs corresponded to rare microdeletion/ microduplication syndromes. Conclusions: This study reports rare CNVs or syndromes among Turkish patients with ID with/without other medical conditions. Data revealed an overall diagnostic rate of 11.43%, which confirms aCGH as the first-line technology allowing geneticists to diagnose complex phenotypes, identify candidate genes involved in ID, and explore novel CNV effects.