Case Presentation: A 29 year old male presented with four months of painful swelling in his hands, ankles, and feet, along with night sweats and fevers. Work-up revealed mild elevations in ESR and CRP along with normal RF and anti-CCP antibodies. He was diagnosed with seronegative rheumatoid arthritis and started on hydroxychloroquine and prednisone. The doses of both medications were progressively increased until approximately 5 months from the initial visit, when he was prescribed etanercept given the continued lack of improvement. Three days after administration of etanercept, he began spiking fevers to 103℉ and developed worsening bilateral knee swelling and warmth. Cultures from incision and drainage of a right knee abscess and right knee arthroscopy grew Mycobacterium abscessus. He was started on IV amikacin, imipenem, and azithromycin. A week later he developed worsening pain and swelling of the left knee with recurrent fevers and underwent left knee arthroscopic irrigation and debridement with similar culture results.Based on sensitivities he was treated with amikacin, imipenem, clofazamine, and tigecycline with plans for a prolonged course.Approximately a month after beginning treatment, he was again hospitalized for fevers, rigors, and worsening swelling of the left knee. MRI revealed bilateral osteomyelitis of the distal femurs, proximal tibias, and right fibula along with numerous small abscesses, and moderate knee joint effusions with enhancing synovium. Orthopedic surgery felt that no surgical intervention would be beneficial at that time, although bilateral amputation may be necessary for source control. He was discharged with the plan for 12 weeks of IV antibiotics followed by over a year of oral antibiotics for continued suppression, in hopes of avoiding need for amputation.

Discussion: Nontuberculous mycobacteria (NTM) are opportunistic pathogens commonly found in the environment. M. abscessus is most often seen in skin and soft tissue infections occurring through direct contact of broken skin with contaminated water or soil, or secondarily via disseminated disease. This patient was an electrical linesman working in standing water during post-hurricane relief efforts and developed leg abrasions due to a wire brush. The clinical worsening after the addition of immunosuppression was evidence that an alternative diagnosis other than a rheumatologic etiology should have been considered. A study of 14 patients with NTM musculoskeletal infections revealed half of these patients were on immunosuppressive medications at the time of diagnosis and median interval between symptom onset and diagnosis was 7.5 months. In this patient’s case there was approximately a 5 month interval between symptom onset and diagnosis of NTM infection. Treatment for M. abscessus disease usually involves combination therapy with a macrolide with IV amikacin plus cefoxitin or imipenem along with surgical debridement. In our patient, macrolide resistant M. abscessus led to a more complicated regimen. The paucity of data regarding best treatment regimen in macrolide resistant NTM osteomyelitis necessitates the use of a multidisciplinary approach to tailoring antibiotic regimen based on given susceptibilities.

Conclusions: Polyarticular pain is encountered frequently in the care of adults. While often attributed to arthritis, there needs to be increased awareness that NTM infection could present similarly and that delay in diagnosis leads to increased likelihood of requiring amputation.