Abstract

A 81-year-old female presented with a non-healing ulcerated skin lesion on the dorsum of right hand measuring 0.7 cm in greatest dimension. Patient denied any other symptoms. Wide local excision of the skin lesion was performed due to the suspicion of nonmelanoma skin cancer. Microscopic examination of sections reveals superficial and deep acute and chronic inflammation including giant cell reaction along with round to oval cystic spaces rimmed by neutrophils. Abundant Gram positive coryneform bacilli were identified in the neutrophilic cyst. GMS, AFB and FITE stains for other microorganisms are negative. The patient recalled her right hand scratched by pet cat 4 weeks ago. She is missing the second dose of TD vaccine since 1958. The clinical history in conjunction with presence of gram-positive coryneform bacilli in areas of suppuration indicates this is a rare case of cutaneous Corynebacterium species infection. Cutaneous diphtheria most commonly presents in unvaccinated individuals following travel to an endemic area. It is caused by toxin-producing strains of Corynebacterium diphtheriae. However, in rare situation, zoonotic disease can occur due to transmission of other Corynebacterium species (C. ulcerans and C. pseudotuberculosis) via close contact with domestic livestock and pet animals. Bacterial speciation in this case was precluded by the formalin fixation of the specimen when skin cancer was suspected initially. Cutaneous diphtheria rarely results in severe complications. However, if the species are found to produce toxin or the patient presents with related symptoms, the need for antitoxin administration should be evaluated immediately.

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