A suspected case of Lyme disease causing complete heart block

Abstract Carditis is a rare complication of Lyme disease and usually presents in the early dissemination phase, several weeks after exposure to a tick bite. Conduction abnormalities are the most common manifestation of Lyme carditis. The presentation can vary from atrioventricular conduction delay (first-degree atrioventricular conduction block) to life-threatening situations, such as a complete heart block. Although such manifestations occur late, our case report describes an interesting case where the patient developed a complete heart block in the setting of acute Lyme disease. An elevated IgM with negative IgG Lyme serology titer, an unusual finding, initially led us to face a diagnostic dilemma. Our suspicion of a tick bite was affirmed when we detected a positive titer for Babesia microti, an organism carried by the same tick and a common co-infection with Lyme disease. The patient improved with antibiotic therapy and temporary pacemaker support during the initial few days of admission.