Cutaneous diphtheria is a localized skin infection caused by toxigenic and non-toxigenic strains of Corynebacterium diphtheriae - a gram-positive bacillus. It more commonly causes a highly contagious upper respiratory tract infection. More recently, C. ulcerans, C. pseudodiphtheriticum, and C. pseudotuberculosis have also been implicated in cutaneous lesions. Cutaneous diphtheria is endemic in tropical countries but is being increasingly reported in developed countries due to international travel. Declining rates of adult booster vaccination against diphtheria have also played a role. Skin lesions develop when organisms are inoculated into pre-existing lesions such as abrasions, wounds, ulcers, rashes, or burns. Tattooing and intravenous drug use are risk factors. Some cases occur in normal skin. Cutaneous C. ulcerans infection may occur in those who come in contact with infected domestic or agricultural animals.