Objective: To explore the pathogenic genes of long QT syndrome and the correlation between gene mutation and clinical phenotype. Methods: Clinical data of a child with suspected long QT syndrome were retrospectively analyzed

and whole exome sequencing ( WES) was performed to screen the mutations that could lead to long QT syndrome. Pathogenicity scoring

genetic inheritance patterns and Sanger sequencing were used to validate the identified mutation. Results: Genetic testing revealed the heterozygous mutation in KCNH2 gene c. 3100 _ 3109delGACACGGAGC. Various prediction software indicated that the mutation was deleterious. Alphafold analysis suggested that the mutation could lead to protein truncation. Conclusion: The heterozygous mutation c. 3100 _3109delGACACGGAGC in KCNH2 gene is the pathogenic mutation in the child

which may affect the stability of the KCNH2 protein.