Korean J Dermatol.  2022 Feb;60(2):115-119.

Three Cases of Erythema Induratum Diagnosed by Histopathology and Interferon-Γ Release Assay

• Jung SW
• Choi EH

Abstract

Erythema induratum (EI) is a tuberculid caused by a hypersensitivity reaction against Mycobacterium tuberculosis or its metabolic products, but it is usually absent in skin lesions. Interferon-γ release assay (IGRA) has been used for diagnosing M. tuberculosis infection instead of the tuberculin skin test and mycobacterial culture, which have limitations for accurate diagnosis. EI was clinically suspected in our cases, and all of them had a family history of tuberculosis. Histopathological findings were consistent with those of EI. Mycobacterium-reverse blot hybridization assay conducted in two cases was positive for M. tuberculosis, and all cases were positive for IGRA. Herein, we report a case series of EI diagnosed by histopathology and IGRA and then successfully treated with anti-tuberculosis treatments.

Keyword

Erythema induratum; Interferon-gamma release assay; Mycobacterium tuberculosis