A 73-year-old male with history of multiple myeloma (in remission for 3 years after thalidomide and dexamethasone treatment) and chronic cough, presented to the Emergency Department with 3 days of left elbow swelling, which was diagnosed as olecranon bursitis based on clinical presentation and X-ray (Fig. 1). There was no history of elbow trauma. His bursitis improved with a steroid injection but recurred 2 months later and was treated with a repeat steroid injection. Unfortunately, his bursitis recurred again 2 months later, and bursa aspirate yielded a white blood cell (WBC) count of 45,708 with 98% neutrophils, suspicious for septic bursitis. Bacterial cultures were negative, and he had not been on antibiotics previously. He received a 14-day course of cephalexin.
Because the elbow was still edematous after 8 days of cephalexin, he underwent elbow debridement, which revealed purulent fluid with erythematous grayish-brown tissue. Histology showed acutely inflamed synovium consistent with infection. 2 out of 3 samples were smear-positive for acid-fast bacilli. All 3 operative mycobacterial cultures and the initial aspiration grew MAC.
On review of systems, he mentioned a chronic productive cough. The patient smoked a pipe for 10 years but quit 65 years ago. He had no formal diagnosis of COPD. Sputum cultures grew MAC. A chest X-ray showed basal atelectasis and multiple bilateral calcified pleural plaques, consistent with prior asbestos exposure (Fig. 2). There was no significant change compared to a chest X-ray done 3 years prior to presentation, and tuberculosis skin testing was negative. Other exposures included gardening, hot-tub use, and a pet dog.
The MAC isolate was susceptible to rifabutin, ethambutol, and clarithromycin; intermediate to rifampin, streptomycin, and moxifloxacin; and resistant to ciprofloxacin, kanamycin, cycloserine, ethionamide, and amikacin. His initial treatment regimen included clarithromycin 500 mg PO BID, ethambutol 1600 mg PO daily, and rifabutin 300 mg once daily. The rifabutin was discontinued 3 weeks into therapy due to neutropenia and transaminitis. His bursitis resolved after a 12-month course of ethambutol and clarithromycin. Repeat sputum cultures were not obtained after completion of therapy.
One year later, his multiple myeloma recurred, and he was started on lenalidomide and dexamethasone. Around this time, he was also diagnosed with seronegative rheumatoid arthritis (RA) and initiated methotrexate. 3 years after completing his MAC treatment, he underwent an elective right total knee arthroplasty (TKA) for degenerative joint disease. This procedure was performed at an outside facility with presumed peri-operative prophylaxis. One year later, he developed right TKA pain, instability, and swelling. X-ray showed a well-seated right TKA with a large effusion (Fig. 3). C-reactive protein (CRP) was elevated at 13.5 mg/L (reference range < 8 mg/L), and erythrocyte sedimentation rate (ESR) was elevated at 65 mm/h. Synovial fluid aspiration yielded 4524 total nucleated cells; 57% neutrophils, and 39% monocytes. The synovial fluid aspirate grew MAC. He underwent TKA resection with placement of a vancomycin/tobramycin impregnated spacer. Histology was negative for acute inflammation or granulomas. All 4 surgical tissue samples grew MAC. His multiple myeloma chemotherapy and methotrexate for RA were held.
His TKA MAC isolate was still susceptible to ethambutol and clarithromycin. Although it was previously susceptible to rifabutin, it now demonstrated intermediate susceptibility. He was initially started on clarithromycin, ethambutol and rifabutin, but due to recurrent transaminitis and neutropenia, he was continued on dual therapy with ethambutol and clarithromycin for 6 months prior to consideration for reimplantation. Pre-reimplantation CRP was normal at 4.8 mg/L, and ESR was 49 mm/h. Although still on therapy, the right knee synovial fluid was aspirated prior to reimplantation and found to be negative for mycobacterial growth.
Six weeks later, he underwent reimplantation. All 4 surgical tissue samples from reimplantation remained negative for MAC. One of 4 cultures grew coagulase-negative staphylococci, which was considered a contaminant. Pathology was negative for acute inflammation. He continued ethambutol and clarithromycin for another 6 months, to complete a total of 12 months. Then, he was placed on chronic suppression with azithromycin 1200 mg orally once a week. Fifteen months later, he successfully underwent an elective contralateral TKA, again for degenerative joint disease. His multiple myeloma went into remission, precluding further chemotherapy. His methotrexate for RA was switched to hydroxychloroquine. He continues to do well at 7 years of follow-up after the 2-stage exchange of his MAC-infected right TKA.