Background: Although Corynebacterium diphtheriae is well known for causing diphtheria and other respiratory tract infections, in very rare cases it can lead to severe systemic disease.
Case Report: This is a case of a previously healthy young man (no prosthetic valve in situ or other known congenital defect), presenting with a Corynebacterium diphtheriae infection leading to endocarditis. The patient reported no I.V. drug use, so it can be assumed that no risk factors for infective endocarditis were present.
Conclusions: This report aims to raise suspicion for this specific infection in order to proceed with the right treatment as soon as possible.

Keywords: Corynebacterium Infections - microbiology, Anti-Bacterial Agents - therapeutic use, Corynebacterium diphtheriae - isolation & purification, DNA, Bacterial - analysis, Diagnosis, Differential, Echocardiography, Endocarditis, Bacterial - microbiology, Humans, Male, Tomography, X-Ray Computed, young adult