Mycobacterium malmoense is a species of slow-growing nontuberculous mycobacteria. It causes mostly pulmonary
infections or
lymphadenitis in children, but is increasingly encountered in isolated
tenosynovitis in adults. Diagnosis is often delayed because of the rarity of the condition and the difficulty of culturing the bacteria.
CASE PRESENTATION: We report on a rare association of seronegative
polyarthritis with infectious nontuberculous mycobacteria
tenosynovitis. A 65-year-old Caucasian female was referred to our clinic because of persisting
tenosynovitis of the finger flexor tendons of her right hand, despite two previous
synovectomies. She also reported bilateral shoulder and left wrist
pain. Paraclinical investigations showed slightly elevated inflammatory parameters. Ultrasound showed
synovitis of metacarpophalangeal joints of the right hand and right knee, and a bilateral subacromial
bursitis. Hand magnetic resonance imaging also revealed an erosive carpal
synovitis. Bacteriological analysis of the second tenosynovectomy specimen showed no growths in aerobic and anaerobic cultures. An additional synovial fluid analysis of the wrist joint was negative for mycobacteria and crystals. Seronegative
polyarthritis was suspected, but the initiated immunosuppressive treatment with
prednisolone and
methotrexate resulted in no clinical improvement of the
tenosynovitis. Yet the other joints responded well, and the inflammatory parameters normalized. The immunosuppression was later stopped because of side effects. Due to massive worsening of the
tenosynovitis, a third
synovectomy was performed. Mycobacterium malmoense was identified on biopsy, leading to the diagnosis of infectious
tenosynovitis. At this point, we started an antituberculous
therapy, with incomplete response. A combination of antimicrobial and immunosuppressive treatment finally led to the desired clinical improvement.
CONCLUSION: The treatment of nontuberculous mycobacteria
tenosynovitis is not well established, but combining
antibiotics with surgical
debridement is probably the most adequate approach. Our case highlights the importance of having a high clinical suspicion of an atypical
infection in patients with inflammatory
tenosynovitis not responding to usual care.