# Anti-MDA5 Antibody-Positive Dermatomyositis-Associated Interstitial Lung Disease With a False-Positive Tuberculosis-Targeted RNA Capture (TB-TRC) Result: A Multimodal Management

## TL;DR

A patient with a specific type of muscle disease and lung complications had a false test for tuberculosis, requiring careful treatment with multiple therapies.

## Contribution

This case highlights the importance of multimodal therapy and careful interpretation of false-positive TB-TRC results in anti-MDA5 RP-ILD.

## Key findings

- False-positive TB-TRC results can delay appropriate treatment in anti-MDA5 RP-ILD.
- Multimodal therapy including plasma exchange and JAK inhibition improved outcomes in refractory cases.
- Repeat testing confirmed the initial TB-TRC result was a false positive.

## Abstract

Anti-MDA5 antibody-positive dermatomyositis often causes rapidly progressive interstitial lung disease (RP-ILD) with high mortality. We present a 59-year-old man with three weeks of fever and dyspnea whose chest CT images showed bilateral subpleural ground-glass and reticular opacities. A markedly elevated anti-MDA5 titer and skin biopsy confirmed anti-MDA5 anti-positive dermatomyositis-associated RP-ILD. Tacrolimus plus nintedanib was initiated. Initial bronchoalveolar lavage fluid (BALF) testing on admission was unexpectedly positive for Mycobacterium tuberculosis by targeted RNA capture (TB-TRC), precluding cyclophosphamide and prompting plasma exchange, followed by intravenous immunoglobulin (IVIG). Repeat BALF TB-TRC and all sputum cultures remained negative for M. tuberculosis, confirming a false-positive result. On day 28, tofacitinib replaced tacrolimus due to persistent hyperferritinemia. The patient was discharged without home oxygen therapy on day 54. This case highlights the importance of interpreting rapid assays in context and using multimodal therapy - steroids, calcineurin inhibition, antifibrotics, plasma exchange, IVIG, and Janus kinase (JAK) inhibition - for refractory anti-MDA5 RP-ILD.