A novel stop-gain pathogenic variant in the KCNQ1 gene causing long QT syndrome 1

Background: Inherited primary arrhythmias, such as long QT (LQT) syndromes, are electrical abnormalities of the heart mainly due to variants in 3 genes. We herein describe a novel stop-gain pathogenic variant in the KCNQ1 gene in an Iranian child with LQT syndrome 1.

Methods: The patient and his family underwent clinical evaluation, electrocardiographic Holter monitoring, and whole-exome sequencing. Sanger sequencing and segregation analysis were used to confirm the variant in the patient and his family, respectively. The pathogenicity of the variant was checked via an in silico analysis.

Results: The proband suffered from bradycardia and had experienced syncope without stress. The corrected QT interval was 470 ms (the Schwartz score ≥ 3.5), and the Holter monitoring showed sinus rhythm, infrequent premature atrial contractions, and a prolonged QT interval in some leads. Whole-exome and Sanger sequencing showed c.968G > A in 3 affected family members. According to the American College of Medical Genetics and Genomics criteria, c.968G > A was classified as a pathogenic variant.

Conclusions: The KCNQ1 gene is the main cause of LQT syndromes in our population. The common genes of LQT syndromes should be studied in our country's different ethnicities to determine the exact role of these genes in these subpopulations.