Keeping up the beat of Kleefstra syndrome.

Long QT syndrome (LQTS) is a rare and potentially life-threatening arrhythmia characterized by delayed repolarization on electrocardiogram (EKG) evaluation. Although LQTS is primarily associated with defects in ion channels, in approximately 20% of cases the genetic cause remains unknown. Kleefstra syndrome (KS), a rare neurodevelopmental disorder caused by alterations in the EHMT1 gene, has been associated with various cardiac abnormalities, including structural defects and arrhythmias. Here we report the second case of LQT in a patient with KS, strengthening the association between these two conditions. Although rare in KS, LQT may represent a potentially life-threatening condition that requires careful monitoring. Further, we present a detailed clinical case and a literature review on cardiac rhythm abnormalities in KS, highlighting the importance of EKG monitoring in these patients. Further studies are needed to clarify the link between EHMT1 and cardiac arrhythmias and to establish the potential role of EHMT1 in the epigenetic modulation of cardiac pacemakers. These insights may have important implications in management of patients with KS and other Mendelian disorders of epigenetic machinery (MDEMs).