Complete Atrioventricular Block: An Unusual Presentation of Holt-Oram Syndrome

Abstract

Background: Holt-Oram syndrome (HOS) is a rare autosomal dominant disorder characterized by congenital upper limb malformations and cardiac anomalies. While structural cardiac defects such as atrial septal defects (ASDs) are commonly reported, isolated conduction abnormalities as the initial manifestation are unusual. Case Presentation: We report the case of an 18-year-old female who presented with exertional syncope. Electrocardiography revealed a third-degree atrioventricular (AV) block with a ventricular rate of 35 bpm. Physical examination demonstrated bilateral radial deformities and thumb hypoplasia. Genetic testing revealed a pathogenic TBX5 mutation, confirming Holt-Oram syndrome. A dual-chamber pacemaker was implanted with favorable clinical evolution. Discussion: This case underscores the importance of considering syndromic causes in young patients with unexplained conduction abnormalities, especially when skeletal anomalies are present. Early diagnosis facilitates optimal management, genetic counseling, and family screening. Conclusion: Holt-Oram syndrome should be considered in young patients with syncope and AV block, particularly in the presence of congenital upper limb deformities.