We present a rare case of tuberculous myositis in a 36-year-old man with long-standing ankylosing spondylitis treated with adalimumab. We review the association between antitumor necrosis factor therapy and tuberculous myositis. Our case illustrates that the index of suspicion of tuberculosis in these patients, even with atypical clinical features, must be very high and emphasizes that this rare infection may occur even with negative tuberculosis screening before therapy was started.