Copy number variation analysis in 189 Romanian patients with global developmental delay/intellectual disability.

BACKGROUND: Developmental delay and intellectual disability represent a common pathology in general population, involving about 3% of the pediatric age population, the genetic etiology being often involved. The aim of this study was to determine the clinically relevant copy number variants in patients diagnosed with global developmental delay/intellectual disability in our population, using the chromosomal microarray analysis. METHODS: We analyzed 189 patients diagnosed with global developmental delay/intellectual disability, presented in Clinical Emergency Hospital for Children, Cluj-Napoca. The patients were completely clinically investigated, including dysmorphic and internal malformations evaluation, psychiatric, neuropsychological and metabolic evaluation, standard karyotyping. Genomic analysis was done using chromosomal microarray analysis. RESULTS: Pathogenic findings (including uniparental disomy) and variants of unknown significance were detected in 53 of 189 patients (28.04%). Pathogenic copy number variants and uniparental disomy were observed in 35 of 189 patients (18.51%). Two patients presented uniparental disomy for chromosome 15, one with clinical phenotype of Prader-Willi syndrome and the other with clinical phenotype with Angelman syndrome. Within the category of pathogenic findings, the recurrent copy number variants were seen in 21 of 35 patients (60%). CONCLUSIONS: The increased percentage of pathogenic structural variants observed in patients with global developmental delay/intellectual disability analyzed by chromosomal microarray technique supports its use in patients with a non-specific phenotype such as these neurodevelopmental disorders. The high percentage of recurrent pathogenic variants between these findings is a finding that support their initial evaluation when a genetic testing algorithm could be a useful option.

Diagnostic Usefulness of MLPA Techniques for Recurrent Copy Number Variants Detection in Global Developmental Delay/Intellectual Disability.

BACKGROUND: Genetic testing has become a standardized practice in the diagnosis of patients with global developmental delay/intellectual disability (GDD/ID). The aim of this study is to observe the frequency of recurrent copy number variations (CNVs) in patients diagnosed with GDD/ID, using MLPA technique. METHODS: A total of 501 paediatric patients with GDD/ID were analysed using SALSA MLPA probemix P245 Microdeletion Syndromes-1A, and the technical steps were performed according to the MRC Holland MLPA general protocol. RESULTS: Twenty-five of 501 patients (5%) were diagnosed with a microdeletion/microduplication syndrome. Amongst them, 7 of 25 (30%) with clinical suggestion have a confirmed diagnosis, for the other cases the clinical features were not evocative for a specific syndrome. CONCLUSION: This study showed that in cases with a specific clinical diagnosis the MLPA technique could be a useful alternative, less expensive and more efficient to indicate as first intention of a targeted diagnostic test, as it is the case of Williams syndrome, Prader-Willi syndrome or DiGeorge syndrome.