RESUMO
Tuberculosis [TB] is a chronic granulomatous infection which can present in an atypical form. Isolated muscle involvement is very rare. We report a 25-year-old man who presented with a massive cystic swelling on the right side of his back, extending from the lower thoracic to the gluteal region. He had a history of contact with a friend who was suspected of having TB. Magnetic resonance imaging [MRI] showed that the origin of the cyst was from the erector spinae muscles. The result of a fluid aspirate showed acid fast bacilli. The swelling disappeared after treatment with anti-tuberculous medications. Muscular involvement in TB is very rare. In our patient, the reports of an ultrasound and MRI confirmed isolated muscle and subcutaneous involvement without bony lesions. This case is reported to increase physician awareness regarding soft tissue TB. Although it is rare, similar cases may be seen in the future