Erythema Induratum Caused by Mycobacterium chelonei in an Immunocompetent Patient.

Erythema induratum is a disease characterized by nodules on the flexural surface of the lower legs strongly associated with Mycobacterium tuberculosis infection. In the presented case, erythema induratum was found in a middle-aged woman caused by an atypical mycobacterium, Mycobacterium chelonei, identified via culture. Mycobacterium chelonei is best known for its pathogenicity in immunocompromised hosts and has been reported secondary to traumatic implantation. However, the patient described in this case did not have any comorbidities associated with erythema induratum, had a negative purified protein derivative skin test, and was immunocompetent. Disease resolution was achieved with clarithromycin and doxycycline therapy.