[Explore the value of whole exome sequencing in early diagnosis for children with language delay/disorder]

Objective: To evaluate the utility of whole-exome sequencing (WES) in early diagnosis for children with language delay/disorder. Methods: Children with language delay/disorder who were admitted to the Department of Health Care, Children's Hospital Affiliated to the Capital Pediatric Institute from January 2019 to December 2020 were analyzed retrospectively. Based on informed consent, the peripheral blood of the children and their parents was collected for WES. Combining the clinical phenotypes of the children, the candidate variants, including single nucleotide variants (SNVs) and copy number variations (CNVs), were selected for validation and family segregation analysis using Sanger sequencing, real-time PCR or CNV-Seq. The pathogenicity of variants was evaluated based on ACMG guideline following with finial genetic diagnosis. Based on whether genetic diagnosis was achieved or not, 125 children with comprehensive examination of the Children Neuropsychological and Behavioral Scale(CNBS-R2016) were sub-grouped (positive/negative group), and the total scores and the detailed scores of five developmental sections (gross motor, fine motor, adaptive ability, language and social behavior ability) between two subgroups were compared. Results: A total of 165 children with language delay/disorder were recruited, including 109 males and 56 females. The ratio of boys to girls was 1.95∶1.The age of the children was (3.2±1.2) years old, the median age was 3.0 years. 45 children carry disease-related pathogenic/likely pathogenic variants, including 36 SNVs and 9 CNVs. The genetic diagnostic yield of this cohort was 27.3% (45/165). The inheritance analysis for core family members showed de novo variant accounted for 86% of genetic diagnosis (31/36). The positive diagnosis rate in girls was 45% (25/56), which was significantly higher than that in boys (18.3%, 20/109, χ²=12.171, P<0.05). There was no significant difference in the rate of positive diagnosis among all age groups (χ²=4.349, P>0.05). Interestingly, the scores of gross motors of positive group were significantly lower than that of negative group (61.5 vs. 69.4, t=-2.610, P<0.05). Otherwise, no significant difference was seen between two groups(t=-0.933, -1.298, -0.114, -0.214, all P>0.05). Conclusions: Language delay/disorder has complex genetic heterogeneity. WES has important application value in early etiological diagnosis for children with language delay/disorder.