Fatal pancarditis in a patient with coexistent Lyme disease and babesiosis. Demonstration of spirochetes in the myocardium.

A 66-year-old man developed fever, chills, myalgias, three erythematous skin lesions, and transient left eyelid lag. Because of persistent fever, he was hospitalized 4 weeks after the onset of disease; a peripheral blood smear showed Babesia microti in 3% of his erythrocytes. Eighteen hours later, he died unexpectedly. Autopsy showed pancarditis with a diffuse lymphoplasmacytic infiltrate, and spirochetes were found in the myocardium. Antibody titers to both the Lyme disease spirochete Borrelia burgdorferi and Babesia microti were elevated. The finding of spirochetes in the myocardium and the elevated antibody titers to Borrelia burgdorferi suggest that the patient died from cardiac involvement of Lyme disease.