Prajapati V, Steed M, Grewal P, Mahmood MN, Verma G, Brassard A. Erythema induratum: case series illustrating the utility of the interferon-γ release assay in determining the association with tuberculosis.
J Cutan Med Surg 2013;
17 Suppl 1:S6-S11. [PMID:
24144256 DOI:
10.2310/7750.2013.wound4]
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Abstract
BACKGROUND
The interferon-γ release assay (IGRA) is a novel method for detecting previous sensitization to tuberculosis (TB). Despite having several advantages over the tuberculin skin test (TST), including higher specificity and no influence from past bacille Calmette-Guérin (BCG) exposure, there are a limited number of reports describing its application in patients with erythema induratum (EI)/nodular vasculitis (NV), which is usually but not always related to TB.
OBJECTIVES
The aim of our case series was to evaluate the usefulness of the IGRA for determining a TB association in patients with EI/NV.
METHODS
Retrospective chart reviews were conducted on four patients diagnosed with EI/NV at our institution in whom an IGRA had been performed.
RESULTS
All four subjects had positive TST results. The IGRA was also positive and therefore supported a link with TB in two cases. One patient responded completely to anti-TB therapy, whereas the second was lost to follow-up. Both cases unrelated to TB, by virtue of negative IGRAs, demonstrated complete response to immunosuppressive therapy (methotrexate), with one individual having failed anti-TB therapy first.
CONCLUSION
Our case series highlights the utility of the IGRA for establishing a TB association in patients with EI/NV. Although limited by a small sample size, we propose adjunctive use of this test at the time of EI/NV diagnosis, especially in the setting of previous BCG exposure, so that management can be tailored according to whether an underlying relationship with TB exists.
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