While Corynebacterium ulcerans can mimic classical diphtheria, extrapharyngeal infections are extremely rare. Sequencing of the diphtheria toxin (DT)-encoding tox gene of two C. ulcerans isolates from extrapharyngeal infections revealed differences from C. diphtheriae DT sequences, mainly in the translocation and receptorbinding domains. C. ulcerans supernatants were much less potent than supernatant from C. diphtheriae. A C. ulcerans DT-specific PCR is described below.Among the pathogenic nondiphtheria corynebacteria, Corynebacterium ulcerans has only rarely been reported to cause disease in humans (8,15). Nearly all cases which had come to clinical attention were characterized by pharyngeal infections mimicking classical diphtheria. This has been explained by the fact that in similarity to Corynebacterium diphtheriae and Corynebacterium pseudotuberculosis, C. ulcerans may harbor lysogenic -corynephages coding for the diphtheria toxin (DT) which is responsible for the systemic symptoms caused by C. diphtheriae. Recently, several reports of severe C. ulcerans infections causing pseudomembrane formation (3,6,14,21) and the isolation of C. ulcerans from domestic cats (20) alerted public health professionals involved in diphtheria control in Europe and the United States and prompted a change in the guidelines on control of toxigenic C. ulcerans in the United Kingdom (J. M. White, N. S. Crowcroft, A. Efstratiou, K. Engler, G. Mann, and R. C. George, Abstr. Publ. Health Lab. Serv. Annu. Conf., abstr. 50, 2001). In contrast to C. ulcerans infections leading to classical diphtheria-like symptoms, extrapharyngeal manifestations of C. ulcerans are extremely rare (22).As a consequence of increased awareness of potentially severe C. ulcerans infections, the German Consiliary Laboratory on Diphtheria, which was established at the Max von Pettenkofer-Institute in 1997, started to characterize and collect C. ulcerans strains sent from different German laboratories for further differentiation and DT determination. Since 1997, isolates from two cases of human C. ulcerans infections came to the attention of our institute. In both cases, patients presented with an extrapharyngeal manifestation of C. ulcerans infection. One patient died from a severe necrotizing sinusitis caused by a toxigenic C. ulcerans strain (designated A2911) detected by tox PCR and Elek testing (23). The other patient was infected by a tox-positive C. ulcerans strain named A6361.Case reports. A 40-year-old homeless alcoholic and drugusing patient received a deep skin ulceration on his right leg after falling down an escalator in the station area of a major German city. The patient denied having had contact with animals (including cattle and sheep), visiting rural areas, and traveling outside Germany in the previous few months. There was no fever and only slight redness of the wound. A swab that was obtained from the skin wound showed coryneform, grampositive rods after Gram staining. After 24 h of incubation on sheep blood agar at 37°C in 5% CO 2 , whitish,...