A 50-year-old woman presented with a mass in the right calf for 4 months. There were no symptoms of cough or weight loss, and no history of intramuscular injection at the site concerned or of any contact with TB. Physical examination revealed an indurated nodule with no tenderness or elevation of local temperature, about 8 x 5 cm in size. The borders of mass were not well-demarcated. There was no abnormality of distal vascularity or sensation, and no limitation of movement. Laboratory tests revealed a normal blood count, and liver function tests, ASO titers, and renal functions were not deranged. An extensive laboratory workup, including ANA, ANCA, CRP, tumor marker levels, thyroid function tests, and inflammatory markers, returned results within normal limits. The outcomes of several infection tests for syphilis, hepatitis B, hepatitis C, and HIV were negative.
Ultrasound of the right calf was performed in case 2 and suggested a hypoechoic lesion. The patient in case 2 also underwent musculoskeletal MRI examination, and the result showed similar lesions to case 1 in the soleus muscle and medial posterior part of the right tibia and fibula (Figures 1E, F). According to radiological imaging findings, both patients had other painless muscular nodules at multiple sites throughout their entire bodies.
Resections and histopathologic observations of lesions were performed in case 2. Granulomatous inflammation, mainly composed of epithelioid histiocytes and Langerhans giant cells, was observed under the microscope (Figure 1H). Histopathologic examination showed the presence of non-necrotizing epithelioid granulomas compatible with TB. Immunohistochemistry against CD4/CD8, MHC-I, and MAC (C5b9) was negative. Moreover, the acid-fast bacilli stain was negative. PCR for TB was positive in case 2 in paraffin-embedded and frozen sections of muscles. A diagnosis of MT was considered in case 2, despite the lack of detectable focus of tubercular infection except in the PCR and histopathology results.
Many differential diagnoses were considered in both cases, including deep vein thrombosis, a soft tissue tumor, or a pyogenic abscess. Based on the diagnosis of MT, the patients in cases 1 and 2 were both prescribed standard oral antituberculosis treatment with four drugs, namely, isoniazid, rifampicin, ethambutol, and pyrazinamide, for 2 months. After treatment, the patients' symptoms were relieved, and the nodules in the calves appeared to decrease in size. Further courses of isoniazid and rifampicin were administered. At the time of writing, the patients are undergoing follow-up.