A 34-year-old man injured his right wrist on the tidal flats. One year later, he visited a local clinic with right wrist pain. Stenosing tenosynovitis was diagnosed and conservative treatment was performed. However, his symptoms persisted for approximately two years after the injury. At another hospital, tenosynovitis with NTM infection was suspected. Therefore, the patient was treated with a combination of radical debridement twice and antibiotics. As for antibiotics, clarithromycin, levofloxacin and rifampicin were administrated for one month from the first surgery to the second surgery. After that, clarithromycin, minocycline, ethambutol and garenoxacin were administrated for five months. However, tenosynovitis did not improve. Six months later, he was referred to our hospital. A physical examination revealed right thenar muscle atrophy and a sensory disorder in the index and middle fingers and on radial side of the ring finger. Semmes-Weinstein monofilament test was 4.56 (red). Range of motion (ROM) was restricted from the index finger to little finger (Table 1). A soft tissue defect was observed on the flexor side of the wrist, which exposed the flexor tendon and median nerve (Figure 1). Laboratory results were normal, except for a C-reactive protein level of 0.1 mg/dL. Magnetic resonance imaging (MRI) revealed hypertrophy of the synovial sheath (Figure 2). The cause was also diagnosed as NTM infection, which was consistent with the previous diagnosis, and was treated with a TPF flap. When the dead space was released during surgery, the wound was filled with an inflamed synovial sheath (Figure 3(A)). The synovium was completely debrided and the carpal tunnel was released. Tenolysis of the flexor tendon and neurolysis of the median nerve were performed. A TPF flap was harvested from the right temporal region (Figure 3(B)). After wrapping the median nerve with the flap, it was inserted between the flexor digitorum superficialis (FDS) tendon and flexor digitorum profundus (FDP) tendon, and then folded onto the FDS tendon (Figure 3(C)). The superficial temporal artery and radial artery were anastomosed end-to-side, then the superficial temporal vein and radial vein were also anastomosed end-to-end. The anastomosis was performed within the lesion, but in a relatively scarless area. A full-thickness skin graft was harvested from the abdomen and grafted onto the flap (Figure 3(D)). Pathological findings of the resected synovium stained with hematoxylin & eosin (HE) revealed epithelioid cell granuloma (Figure 4(A)); however, Ziehl-Neelsen staining did not show any specific findings (Figure 4(B)). Two types of cultures with incubations at 3 and 30  C, a polymerase chain reaction (PCR) using specific nucleotides for M. tuberculosis, M. intracellulare, and M. avium, and a genetic test targeting other bacteria did not reveal any infection. Antibiotic treatment using clarithromycin and minocycline was performed for 4 months after surgery. The ROM of the right fingers recovered in the six years following surgery (Table 2). The sensory disorder was also recovered to the degree of 2.83 (green) in Semmes Weinstein Monofilament test. No recurrence has been detected (Figure 5).