Erythema induratum in a patient with active tuberculosis of the axillary lymph node: IFN-gamma release of specific T cells.

A 57-year-old woman with tender nodular lesions on her legs, arms, buttocks and face is reported as a case of erythema induratum (EI) with active tuberculosis of axillary lymph nodes. Both skin nodular lesions and lymph nodes responded positively to antituberculous therapy. The patient's peripheral blood mononuclear cells showed a high proliferation and produced interferon-gamma (IFN-gamma) in response to purified protein derivative (PPD). These findings indicate the possibility that PPD-specific T cells, capable of producing IFN-gamma, are likely to be involved in the formation of EI as a type of delayed-type hypersensitivity response to mycobacterial antigens at the site of skin lesions.