Background.. Tenosynovitis of the hand and forearm of mycobacterial etiology is an extremely rare form of extrapulmonary tuberculosis, this nosology occurs in 5% of cases of tuberculosis of the musculoskeletal system and can lead to permanent disability of patients. Case report. We present a rare clinical case of widespread tenosynovitis of tendons of all flexors of the hand and fingers of the right upper limb caused by Mycobacterium tuberculosis (MBT). The patient came to the consultative department with complaints about the presence of a formation on the palm surface of the right hand, from which a discharge in the form of "rice grains" periodically spontaneously arises. According to the results of the MRI examination, a picture of peritendinal, synovial, cystic formation along the volar surface of the hand, wrist joint, with the presence of multiple chondromic bodies, tendinitis and tenosynovitis of the flexors of the IV, V fingers of the hand was revealed. He has surgical treatment: removal of neoplasms, pathological tissues and total synovectomy. The intraoperative material was sent for PCR examination, the DNA of the mycobacterial tuberculosis complex was revealed. Conclusion. The presented clinical case demonstrates the importance of performing an MRI examination for tenosynovitis of unclear etiology before surgery and the need for histological and bacteriological examination of intraoperative material. The transportation of the obtained tissues for the above studies should be carried out without the use of formalin in order to exclude false negative laboratory results. In the treatment of patients with immunocompromising diseases, there should be caution against non-specific infections, including Mycobacterium tuberculosis. The presence of limb neuropathy in the patient, instrumental signs of the second or third stage of tuberculous tenosynovitis according to the Kanavel A.B. classification are indications for surgical treatment.