Sinus Node Dysfunction Requiring Permanent Pacemaker Implantation in a Young Adult with Klinefelter Syndrome

BACKGROUND Klinefelter syndrome is the most common genetic cause of male infertility and affects approximately 1 in 500 live births. Although accompanying cardiac disorder is not a specific feature of Klinefelter syndrome, rarely associated anomalies such as mitral valve prolapse, atrial septal defect, ventricular septal defect, tetralogy of Fallot, patent ductus arteriosus, and hypertrophic obstructive cardiomyopathy have been reported. A clear association between Klinefelter syndrome and arrhythmic disorders has not yet been demonstrated. CASE REPORT We report a case of a sinus node dysfunction that required permanent pacemaker implantation in a young adult with Klinefelter syndrome. The patient was consulted to cardiology clinic due to bradycardia. On physical examination, no cardiac abnormality was detected except for bradycardia. Holter results showed sinus arrhythmia with a minimum heart rate of 33 bpm and maximum of 154 Bpm. There were 3612 ventricular premature beats, 30 ventricular pairs, 804 supraventricular premature beats, 7 supraventricular pairs, and 4 supraventricular runs, the longest of which was 5 beats. The patient had defined dizziness and nausea during Holter monitoring. Electrophysiological study (EPS) was planned because existing findings indicated risk of cardiac syncope. Findings of EPS were interpreted as sinus node dysfunction. A permanent pacemaker implantation was performed and the patient has been free of symptoms since. CONCLUSIONS This concomitance should be kept in mind when examining patients with Klinefelter syndrome with bradycardia and/or syncope. It is easily mistaken for epilepsy, which is a commonly encountered abnormality in Klinefelter syndrome.