Diagnostic approach with genetic tests for global developmental delay and/or intellectual disability: Single tertiary center experience.

The child with global developmental delay (GDD)/intellectual disability (ID) is deserving of the appropriate evaluation available for improving the health and well‐being of patients and their families. To better elucidate the diagnostic approach of genetic tests for patients with GDD and/or ID, we evaluated the results in a cohort of 75 patients with clinical features of GDD and/or ID who were referred for diagnostic workup. A total of 75 children were investigated for GDD or ID in the pediatric neurology department. Ten patients (13%, 10/75) with a clinically recognizable syndrome were diagnosed by single‐gene analysis. Next, chromosomal microarray was performed as a first‐tier test, and 25 patients (33%, 25/75) showed structural abnormalities. Then, two fragile X syndrome (3%, 2/75) were confirmed by FMR1 gene fragment analysis. Thirty‐eight remaining patients received a gene panel by next‐generation sequencing. Eight patients were found to have an underlying genetic etiology: CHD8, ZDHHC9, MBD5, CACNA1H, SMARCB1, FOXP1, NSD1, and PAX6. As a result, 45 patients (60%, 45/75) had been diagnosed by genetic tests. Among 30 undiagnosed patients, brain structural abnormalities related to GDD/ID were observed in eight patients (11%, 8/75). However, in 22 patients (29%, 22/75), the causes of GDD/ID remained uncertain. A genetic diagnostic approach of GDD/ID by sequential molecular analysis can help in the planning of treatment, assigning the risk of occurrence in siblings, and providing emotional relief for the family. [ABSTRACT FROM AUTHOR]