Application of the QuantiFERON®-TB Gold test in erythema induratum.

Erythema induratum (EI) was originally described by Ernest Bazin in 1861 as nodular lesions on the legs in association with tuberculosis (TB). A 33-year-old woman was referred to our hospital with tender ulcerative nodules on her legs. Skin biopsies revealed lobular inflammation of the subcutaneous fat with vasculitis. Although conservative treatment was given, the lesions did not improve. Several months later as the lesions persisted, we suspected a TB infection and additional tests were performed. The chest roentgenogram results were normal. The skin biopsies were negative for acid-fast bacilli (AFB). Mycobacterial cultures of the blood and skin were negative. However, the QuantiFERON®-TB Gold test was positive, which led to a diagnosis of latent TB infection being made. The patient was treated with multidrug antituberculosis therapy, which successfully resolved her skin lesions. Therefore, reported herein is the application of the QuantiFERON®-TB Gold test for the confirmation of latent TB infection in EI patients.