[Clinical phenotype and genetic analysis of a child with Intellectual developmental disorder and epilepsy due to variant of CLTC gene].

Objective: To explore the clinical features and genetic basis for a child with Intellectual developmental disorder (IDD) and epilepsy.

Methods: A child who was admitted to the Children's Medical Center of the Affiliated Hospital of Guangdong Medical University in February 2021 was selected as the study subject. Clinical data of the child was collected. Peripheral blood samples of the child and her parents were collected and subjected to whole exome sequencing (WES). Candidate variant was verified by Sanger sequencing.

Results: The patient, a 3-month-and-27-day female infant, had developed the symptoms in the neonatal period, which included severe developmental delay, respiratory difficulties and pauses, increased muscle tone of four limbs, feeding difficulty, and seizures. Cerebral MRI revealed bilateral cerebellar hypoplasia, and video EEG showed slightly increased sharp waves emanating predominantly from the right parietal, occipital, and posterior temporal regions. WES revealed that she has harbored a missense c.3196G>A (p.Glu1066Lys) variant of the CLTC gene, which was confirmed to be de novo by Sanger sequencing. Based on the guideline from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PS2+PM2_Supporting+PP3).

Conclusion: The c.3196G>A (p.Glu1066Lys) missense variant of the CLTC gene probably underlay the pathogenesis in this child. Above finding has facilitated her diagnosis and treatment.