Cutaneous ulcers revealing diphtheria: A re-emerging disease imported from Indian Ocean countries?

INTRODUCTION:Diphtheria due to Corynebacteriumdiphtheriae (C. diphtheriae) has become rare in developed countries. In France only 10 cases of toxigenic diphtheria have been reported since 1989, in all cases causing pharyngitis and all emanating from endemic countries with exception of one contact case. We report herein 13 cases with cutaneous diphtheria, in 5 of which diphtheria toxin was produced, and all imported into France between 2015 and 2018. OBSERVATIONS:Thirteen patients aged 4 to 77 years presented painful and rapidly progressive round ulcerations of the legs, that were superficial and in some cases purulent, with an erythematous-purple border covered with greyish membrane. Bacteriological sampling of ulcers revealed the presence of C. diphtheriae. Only 6 patients had been properly immunized over the preceding 5 years. DISCUSSION:These cases underline the resurgence of cutaneous diphtheria and the circulation of toxigenic strains in France following importation from Indian Ocean countries. This may constitute an important reservoir for ongoing transmission of the disease. Re-emergence of this pathogen stems from the current migratory flow and decreased adult booster coverage. CONCLUSION:Cutaneous diphtheria should be considered in cases of rapidly developing painful skin ulcers with greyish membrane, especially among patients returning from endemic areas, regardless of their vaccination status. The clinician should order specific screening for C. diphtheriae from the bacteriologist, since with routine swabbing Corynebacteriaceae may be reported simply as normal skin flora. Vaccination protects against toxigenic manifestations but not against actual bacterial infection. Early recognition and treatment of cutaneous diphtheria and up-to-date vaccination are mandatory to avoid further transmission and spread of both cutaneous and pharyngeal diphtheria.