[Genetic and clinical analysis of two children with microcephaly and mental retardation due to a frameshifting variant of CASK gene].

Objective: To explore the clinical and genetic characteristics of two children with mental retardation and microcephaly.

Methods: Two children who had visited the Anhui Children's Hospital respectively on March 12 and June 22, 2021 were selected as the study subjects. Peripheral venous blood samples were collected from them and their parents, and subjected to chromosomal karyotyping and whole exome sequencing analyses. Candidate variants were verified by Sanger sequencing and pathogenicity analysis.

Results: Chromosomal karyotyping and copy number detection of the two children had found no abnormality. Whole exome sequencing revealed that child 1 has harbored a c.471delT (p.Pro157Profs*9) frameshifting variant of the CASK gene, whilst child 2 has harbored a c.1259_1269delCTGAGAATAAC (p.Pro420fs*27) frameshifting variant of the CASK gene. Sanger sequencing confirmed that both variants were de novo in origin. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP), both variants were rated as pathogenic (PVS1+PS2+PP3).

Conclusion: The de novo variants of the CASK gene probably underlay the pathogenesis of mental retardation and microcephaly in both children.