Tuberculosis infection in patients with dermatomyositis.

Patients with dermatomyositis (DM) are particularly susceptible to opportunistic infections due to immunosuppression induced by the disease itself and its treatment. We describe three patients who met the diagnostic criteria for DM and developed tuberculous myositis. The first case, a 54-year-old woman, had a positive polymerase chain reaction (PCR) for Mycobacterium tuberculosis detected in a post-mortem muscle biopsy. A second patient was diagnosed with a positive Ziehl-Neelsen stain in bronchoalveolar lavage, and a third patient, with multiple collections in the thorax and lower limbs, had positive Ziehl-Neelsen stain and PCR for Mycobacterium tuberculosis. In inflammatory myopathies, muscle and soft tissue infection by tuberculosis may produce symptoms similar to the underlying disease. The differential diagnosis of tuberculosis superinfection can be difficult.