Corynebacterium diphtheriae Septic Arthritis: A Case Report and Literature Review

Classical respiratory diphtheria, characterised by membranous pharyngitis caused by the gram-positive bacterium <i>Corynebacterium diphtheriae</i>, has become increasingly rare due to widespread vaccination. However, invasive manifestations such as septic arthritis and bacteraemia, while still exceptionally rare, are being reported more frequently, particularly in unvaccinated or partially vaccinated individuals and in cases involving non-toxigenic strains. This case describes a 19-year-old man who presented with various systemic symptoms along with left elbow swelling, initially thought to be reactive arthritis. He was later diagnosed with septic arthritis and bacteraemia secondary to a non-toxigenic strain of <i>C. diphtheriae</i> based on the culture result. Treatment involves antimicrobial therapy and diphtheria antitoxin. This case highlights the importance of considering unusual manifestations of diphtheria and the role of antibiotics as well as diphtheria antitoxin in managing toxigenic and non-toxigenic strains of <i>C. diphtheriae</i>.