Rare Lyme Carditis Presenting With Complete Heart Block in a Young Adult.

Lyme carditis is a rare, yet highly treatable, manifestation of early disseminated Lyme disease, most commonly presenting as varying degrees of atrioventricular block. We report the case of a 27-year-old male who presented to the emergency department in Michigan, USA, on July 16, complaining of orthostatic dizziness and right-sided upper back pain. An electrocardiogram revealed third-degree atrioventricular block, requiring immediate temporary transvenous pacing and hospitalization. Intravenous ceftriaxone was then initiated. The patient's heart block progressively resolved; the temporary pacemaker was removed on day five of admission, and he was discharged on day six to complete a 21-day course of intravenous antibiotics. Approximately two weeks prior to this visit, he had developed a severe headache, neck stiffness, and tingling in his fingers. He was evaluated in a primary care setting, where serological testing confirmed the diagnosis of Lyme disease, and he began oral doxycycline on July 12. Despite initial improvement in his headache, he presented to the emergency department with orthostatic dizziness and high-grade conduction delay. This case highlights the importance of recognizing subtle extracardiac symptoms of Lyme disease in endemic and at-risk areas to prevent unnecessary permanent pacemaker implantation.