Polymorphic ventricular tachycardia with mutation in KCNJ2: case report.

Polymorphic ventricular tachycardia (VT), particularly in the absence of structural heart disease, has a strong genetic foundation primarily rooted in mutations affecting cardiac ion channels and associated regulatory proteins. Here, we report two patients with polymorphic VT harboring potassium channel subfamily J member 2 (KCNJ2) gene mutations. The first case is a 13-year-old girl presenting with periodic paralysis, polymorphic VT, and a prolonged QT interval. She was sequentially treated with metoprolol, verapamil, amiodarone, moricizine, and mexiletine, along with three radiofrequency catheter ablation sessions, but the therapeutic effect was unsatisfactory. Genetic testing revealed a de novo c.406T > C (p.S136P) variant in the KCNJ2 gene. During a 10-year follow-up period, she never experienced syncope. The second patient is a 5-year-old boy presenting with thumb adduction, polymorphic VT, and a prolonged QT interval. He was treated sequentially with metoprolol and flecainide, and his premature ventricular contraction burden decreased significantly after flecainide therapy. Genetic testing identified a de novo c.652C > T (p.A218T) variant in the KCNJ2 gene. This case report updates our understanding of KCNJ2 gene mutations. Arrhythmias due to KCNJ2 mutations respond poorly to antiarrhythmic drugs, but flecainide may be a promising therapeutic option. Arrhythmias associated with KCNJ2 mutations tend to have a more benign clinical course, but identifying mutation carriers at risk of life-threatening arrhythmias remains challenging.