A previously healthy 67-year-old male presented with a swollen left hand following a laceration to his third digit after working in soil in his yard in June 2013. He also managed three large hobby aquariums. A 10-day consecutive course of cefprozil and clindamycin marginally improved his swelling. However, he returned in October 2013 with worsening stiffness and digital and hand swelling, which resulted in a diagnosis of seronegative rheumatoid arthritis (RA) after consultation with rheumatology. All autoimmune serology was negative, and inflammatory markers were normal. His swollen left hand partially resolved after pulsed dose prednisone (20 mg daily/2 weeks) but worsened again. He then received prednisone (10 mg/day) and sulfasalazine (2 g/day) with incomplete improvement followed by progression with spread to his left elbow. Several aspirations and intra-articular steroid injections of left elbow, wrist, and MCP joints were attempted with minimal improvement. On the presumption that his rheumatoid arthritis was refractory, methotrexate and leflunomide were added.
In January 2014, the patient evolved nodules located on the extensor surfaces of his left arm and hand. New nodules appeared on the ulnar aspect of his thumb, radial aspect of his index finger, styloid process, and mid shaft of the ulna. Due to ongoing disease, the biologic adalimumab (Humira) was started in February 2014. Prednisone and sulfasalazine were discontinued, but methotrexate and leflunomide were continued. Infectious prescreening for his biologic therapy screening occurred one week after receiving the first dose of Humira. A Mantoux test read at 9-millimetres was presumed to be falsely positive after a subsequent negative interferon-gamma release assay (IGRA) test (Quantiferon Gold  In-Tube) was obtained.
After three months of treatment, he continued to have a swollen left olecranon and developed lower extremity nodules also. Several joint aspirations were performed from his wrist and knee (due to swelling), but microscopy and bacterial cultures were negative.
In December 2014 he had worsening of the swelling and pain in the left wrist, metacarpophalangeal joints, elbow, and left knee. Sulfasalazine and prednisone were restarted along with rotation of his biologic to etanercept. This resulted in dramatic worsening of his nodular lesions. An urgent biopsy of a left arm nodule and a synovial fluid aspirate of his left elbow were collected and were both positive for acid-fast bacilli consistent with mycobacterium. His immunosuppressants were immediately discontinued and he was urgently referred to the Tuberculosis clinic. Subsequently, the mycobacterial species was determined by mycobacterial growth indicator tube (MGIT) culture to be Mycobacterium marinum in two additional joint aspirates (left wrist and olecranon bursa) that were grown at reduced temperature. A summary of the patient's clinical course is depicted in Figure 1.