Infectious Cutaneous Diphtheria on a Male's Foot

Description

Seen on the medial aspect of an adult male foot, a sharply demarcated ulcer occupies the skin overlying the distal tibia near the medial malleolus, with erythema extending into the surrounding ankle integument. The lesion sits superficial to the malleolar prominence and adjacent to the retromalleolar groove, a region where thin skin and frequent minor trauma make infections clinically conspicuous. Normal surface contours of the hindfoot and ankle remain intact, helping localize the process to the cutaneous and subcutaneous tissues rather than deeper compartments. Edges matter here. Cutaneous diphtheria from toxigenic Corynebacterium diphtheriae often presents as a chronic, slow-healing ulcer with a dirty gray base or adherent membrane, and it can coexist with pharyngeal carriage even when the skin lesion is the chief complaint. On the foot and ankle, clinicians commonly mislabel such ulcers as venous stasis, diabetic ulceration, or traumatic wounds; this view helps emphasize the characteristically sharp border and the disproportionate persistence that should trigger swab for culture on selective media, tox gene testing, and infection-control precautions. Systemic risk is not limited to the skin, diphtheria toxin can contribute to myocarditis and neuropathy, so prompt recognition supports early antitoxin consideration alongside antibiotics such as erythromycin or penicillin and verification of immunization status. Use this image in infectious disease and dermatology teaching to contrast toxin-mediated bacterial ulcers with vascular and neuropathic etiologies, and in public health materials discussing vaccine-preventable infections that still appear in vulnerable populations. It also fits clinical reference content for emergency, wound care, and travel medicine settings where a persistent ankle ulcer needs a broader differential. Anatomical accuracy verified by SciePro's Medical Advisory Board.