Cutaneous paradoxical inflammatory reaction of erythema induratum of Bazin to standard antituberculosis treatment

Cutaneous tuberculosis (TBC) is rather rare and has diverse clinical presentations relative to host immunity and the number of bacilli present in the tissue. A group of cutaneous lesions called tuberculids represent a strong, delayed-type hypersensitivity reaction to mycobacteria. Among them, erythema induratum of Bazin (EIB) typically presents as tender erythematous nodules that ulcerate and are usually confined to the posterior aspects of the calves. Paradoxical reactions (PRs) to appropriate treatment involving the skin have mostly been described in the setting of miliary tuberculosis. These PRs are encountered in infectious and inflammatory diseases during the institution of appropriate treatment representing a worsening or relapse of disease under treatment or unmasking of subclinical disease. This case report describes a patient with EIB developing a necrotic PR shortly after initiation of antituberculosis therapy. The skin lesions cleared with a topical corticosteroid treatment and continued antituberculosis therapy. It is important to recognize cutaneous PR in the setting of treated cutaneous TBC and to reassure patients about the excellent outcome that can be achieved with continuation of treatment.