Case Presentation: 64-year-old female with non-insulin-dependent type 2 diabetes mellitus presented to the emergency room with a 2-week history of progressive pain and swelling of her left index finger. Prior outpatient evaluation with X-rays and MRI resulted negative, and a Cortisone injection and anti-inflammatories provided no relief. She reported difficulty moving her finger, increased warmth and redness, but denied fever, chills, preceding trauma, drainage, skin rash, or other joint involvement. Examination revealed a swollen, exquisitely tender, erythematous left index finger with edema limiting range of motion. It was fluctuant but with no active drainage. An X-ray showed only soft tissue swelling. ESR, CRP and WBC count were normal. An incision and drainage (I+D) was performed, and the purulent fluid obtained was sent for culture. Pending culture results, empiric antibiotic coverage with Cefazolin and Vancomycin was administered. Her symptoms did not improve, and required a second I+D for samples to be sent for histopathology, acid-fast bacilli (AFB) and fungal testing. An MRI done later revealed a prominent lobulated infectious/inflammatory tenosynovitis involving the second flexor tendons and circumferential soft tissue edema/swelling of the second digit. She was discharged home on Augmentin and Doxycycline to await outstanding culture results. Her histopathology report revealed ‘fragments of fibrinous necrosis with mild acute inflammation and fragments of densely inflamed tissue composed of chronic inflammatory cells, histiocytes and poorly formed granulomas.’ AFB and Grocott’s methenamine silver (GMS) stains were negative for organisms, but AFB culture resulted in Mycobacterium Avium Complex (MAC) sensitive to Ethambutol and Clarithromycin. She was then started on this regimen as outpatient, and had repeat surgical debridements 2 and 5 months later which have been negative.
Discussion: Mycobacterium Avium Complex (MAC) is an atypical mycobacterium that usually manifests as pulmonary infection in immunocompetent adults. In immunocompromised hosts, it is the most common opportunistic non-tuberculous mycobacterial infection seen in patients with Acquired Immunodeficiency Syndrome (AIDS). However, skin and joint involvement are quite rare, particularly in immunocompetent individuals, in which case the causative organisms are usually other atypical mycobacteria. In the literature, there have only been a handful of cases of granulomatous tenosynovitis caused by MAC, and these had a suspected source of inoculation such as hand trauma or previous surgery. Here, we present a rare case of MAC-associated tenosynovitis with a non-apparent inoculation source, a case that has not been described in the literature to date.
Conclusions: Although rare, atypical mycobacterial infection should be considered in patients with soft tissue and musculoskeletal infections unresponsive to broad-spectrum antibiotic therapy, particularly in patients with progressive and prolonged signs and symptoms of infection. These infections are most commonly seen in immunocompromised hosts, but consideration should be given to immunocompetent individuals unresponsive to usual treatment options.