A Cytogenetic Study of Turkish Children with Global Developmental Delay

Global developmental delay (GDD)/intellectual disability (ID) is common in children and its etiology is unknown in many cases. Chromosomal abnormalities are predominant genetic causes of GDD/ID. The aim of this study is to determine the genetic risk factors that may be involved in the etiology of GDD/ID. In this study, 810 children with moderate to severe, clinically unexplained GDD/ID for whom cytogenetic analysis were performed were retrospectively rescreened. The results showed that GDD/ID affected more females than males (2 girls:1 boy). A total of 54 children (6.7%) with GDD showed chromosomal aberrations (CAs): 59.3% of these CAs were structural aberrations, and the rest were numerical aberrations (40.7%). Specifically, inversions, deletions, and reciprocal and robertsonian translocations, which were detected in 1, 0.7, 0.8, and 0.4% of the children, respectively, constituted important categories of structural CAs. Among numerical CAs, classic Turner and mosaics were detected in 1.2% of all children. Trisomy 21 and mosaic trisomy 21 were detected in 1% of the children. Marker chromosomes and 47,XXY karyotypes were found in two children each. Our results suggest that female sex is more affected by CAs among GDD/ID cases, and cytogenetic analysis is useful in the etiological diagnosis of GDD/ID.