Case Report: Two cases of recurrent syncope caused by KCNH2 gene mutation in congenital long QT syndrome

This study presents two cases of congenital long QT syndrome caused by KCNH2 gene mutations. It highlights the critical role of genetic testing in its diagnosis and underscores the importance of early detection and personalized treatment strategies to enhance patient outcomes. Comprehensive clinical data were collected from the patients, including measurements of the QT interval and calculations of the corrected QT interval (QTc) using the Bazett correction formula. Genetic testing identified heterozygous pathogenic variants in the KCNH2 gene in both patients. The variant in Case 1 was a frameshift mutation (c.234_241dup, p.Gln81Leufs*38), located in exon 2 (NM_000238.4). Case 2 carried a missense mutation (c.1841C > T, p.Ala614Val) in exon 7 (NM_000238.4). Predictions from multiple bioinformatics tools were consistent with the pathogenicity of both variants. The findings underscore that early diagnosis and tailored therapeutic approaches are essential for improving the prognosis of individuals with long QT syndrome. It is imperative for clinicians to increase awareness of long QT syndrome, particularly in patients presenting with syncope as an initial symptom, to inform clinical diagnosis, treatment, and prognostic assessment.