A Novel KCNJ2 p.Glu299Ala Variant Associated with Short QT Phenotype and Persistent Atrial Fibrillation in a Child

Short QT syndrome (SQTS) is a rare, inherited cardiac channelopathy characterized by an abnormally shortened QT interval, accelerated ventricular repolarization, and an increased risk of atrial and ventricular tachyarrhythmias, including sudden cardiac death (SCD). We report the case of a 14-year-old girl diagnosed with SQTS presenting with persistent atrial fibrillation and a complex independent neurological background. The patient, with no significant family history of cardiac disease or SCD, was incidentally found to have atrial fibrillation and a markedly shortened QT interval during a routine medical evaluation. Although she remained entirely asymptomatic from a cardiovascular perspective, her medical history was notable for maternal Toxoplasma gondii infection during pregnancy, extreme prematurity, and delayed psychomotor development. Electrocardiographic (ECG) findings consistently demonstrated a short QT interval, and genetic testing revealed a likely pathogenic variant in the KCNJ2 gene, consistent with type 3 short QT syndrome (SQTS3). Despite the initiation of antiarrhythmic therapy, atrial fibrillation persisted and the QT interval remained significantly shortened throughout the 24-month follow-up. This case highlights the diagnostic and therapeutic challenges of managing short QT syndrome in pediatric patients, particularly in those who are asymptomatic yet exhibit sustained atrial arrhythmias. It also highlights the coexistence of cardiac channelopathy and neurological comorbidities, emphasizing the importance of a multidisciplinary approach for these distinct clinical entities.