A 49-year-old male presented with a 9-month history of multiple anatomical site pain, a localized mass, and swelling of thighs (Figure 1) and calves, which gradually increased in size and quantity without systemic symptoms, such as fever, poor appetite, malaise, weight loss, or perspiration during sleep or after strenuous exercise. One month before admission, he complained of similar symptoms that occurred in the left forearm but to a lesser degree and with no mass present. He had a history of pulmonary tuberculosis. One year previously, the patient presented non-infectious posterior uveitis and had been treated with steroid for half a year. There were no systemic symptoms and no history of trauma, family history, or other disease history. His systemic physical examination was normal. Multiple anatomical sites on the thighs and calves contained masses, the borders of which were well-demarcated and cystic in consistency, but they were not fluctuant and there was no tenderness of the mass or increased local temperature. The skin over the mass was normal, with no rash observed. Musculoskeletal ultrasound examination suggested substantive bilateral lesions in the calves. Chest computed tomography (CT) revealed previous pulmonary tuberculosis. The patient underwent a musculoskeletal magnetic resonance imaging (MRI) examination in a local hospital; the results were reported as suggestive for rhabdomyolysis, only according to his history of strenuous exercise. The patient was admitted to the Department of Neurology, Wuhan University, Renmin Hospital, for diagnosis and treatment. Further examinations, including those for hemogram, rheumatoid factor (RF), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), aldolase, lactate dehydrogenase (LDH), fungal G-test, and tumor marker levels, were within normal limits. Anti-nuclear antibodies (ANA) were positive at a dilution of 1:100, and blood parasites were negative. Musculoskeletal MRI (Figure 2) examination showed diffuse abnormal signals on the bilateral calf and thigh muscles, suggesting infectious lesions or myopathy. Electromyography (EMG) examination showed that sensory and motor conduction are normal. There was no abnormal spontaneous activity in the anterior muscles of the double tibia and right medial thigh muscles. Paraspinal muscles [L5, S1] have little abnormal spontaneous activity. Motor unit potentials increased in duration and amplitude in the anterior muscles of the double tibia and right medial thigh muscles. It suggested nerve root damage of both lower limbs (may be root damage). In combination with the clinic, there is a great possibility of considering degeneration. A pelvis and lumbar spine MRI showed mild lumbar disc herniation without other abnormal findings. A deep biopsy (including skin, subcutis, fascia, and muscle) was performed on the right gastrocnemius (including the mass and nearby muscles), and the results showed lymphocytes and plasma cell infiltration into and around non-necrotic muscle fibers without muscle fiber necrosis and regeneration. Moreover, inflammation granulomas (including Langerhans cells, epithelioid cells, and lymphocytes) were visible under the microscope (Figure 3), and CD4(+), CD8(-), MHC-I(+), C5b-9(+) (Figure 4), and acid-fast stain(-) results were observed. Sputum examination revealed no evidence of tuberculosis bacilli, and a tuberculin skin test was negative. However, PCR for the M. tuberculosis complex presented positivity, and a tuberculosis T-SPOT test(+); M. tuberculosis was found in biopsy tissue culture of the mass on the calf. A CT scan revealed no bony erosion. A high-probability diagnosis of granulomatous myositis with M. tuberculosis infection in the thighs and calves was considered on the basis of clinical, MRI, culture, histopathology, and gene test results. Therefore, the patient was prescribed standard oral anti-tubercular treatment with four drugs, isoniazid, rifampicin, ethambutol, and pyrazinamide, for 2 months. After treatment, the patient's symptoms were relieved, and the swelling in the thighs and calves appeared to decrease in size. Further isoniazid and rifampicin were given. Currently, the patient is undergoing follow-up.