Should anti-tuberculosis therapy be prescribed in erythema induratum? A case-controlled and incidence correlation study between 2001 to 2020 in Taiwan.

Abstract

Erythema induratum (EI) is a tuberculid associated with Mycobacterium tuberculosis (TB) infection. TB has been identified in Taiwan with a high percentage of EI using PCR. However, this pathogen has rarely been detected recently. To explore the association between EI, annual incidence of tuberculosis in Taiwan, and treatment outcomes over the past two decades. Patients diagnosed with EI between 2001 and 2020 were enrolled based on histopathology, tissue culture, and TB-PCR tests. Other cases of panniculitis with TB-PCR results were used as controls. Their clinical information was obtained. The results were correlated with the annual incidence of tuberculosis and compared between groups. Fifty-five specimens from EI patients fulfilled the inclusion criteria; three (3/55, 5%) had positive TB PCR. One patient diagnosed with erythema nodosum in the control group had positive TB PCR (1/27, 4%). There was no significant relationship between TB and EI (odds ratio = 1.5, 95% confidence interval = -0.964 to 3.964, p = 1). Correlation between the incidence of TB and number of EI cases was not significant (r = -0.185, p = 0.447). Only four patients received anti-tuberculosis therapy. They all showed clinical improvement without recurrence. One patient with PCR-positive EI was not treated with anti-tuberculosis therapy; however, the skin lesion improved 3 months later. No other patients in the EI group were diagnosed with TB infection in the follow up of 508 person-years. Most EI in Taiwan are nodular vasculitis and not tuberculids owing to well-controlled tuberculosis. This condition can be alleviated without anti-tuberculosis therapy.