CLINICAL ANALYSIS OF OSTEOARTICULAR NONTUBERCULOUS MYCOBACTERIAL INFECTION.

Objective: The incidence rate of nontuberculous mycobacterial (NTM) infection has been increasing globally in recent years. However, reports of osteoarticular NTM infection are relatively rare. We report the characteristic clinical features of patients with osteoarticular NTM infection.

Patients and methods: We examined 14 patients with osteoarticular NTM infection (mean age, 68 years) were treated in our hospital in the 20 years between 1995 and 2015.

Results: The rate of osteoarticular NTM infection in whole osteoarticular infection during the same period in our hospital was 2.7%. The NTM species. isolated from the 14 patients included Mycobacterium avium (n = 7), M. intracellulare (n = 5), M. fortuitum (n = 1), and M. kansasii (n = 1). Twelve patients had spinal involvements, and their levels were categorized as thoracic (n = 3), lumbar (n = 4), thoracolumbar (n = 1), and cervicothoracic (n = 4), with an average number of affected vertebra of 4.4. Nine patients had pulmonary lesions, including fibrocavitary (n = 5) and nodular/ bronchiectatic types (n = 4). Nine patients had lesions in sites other than the spinal and pulmonary regions, including the skin (n = 6), rib (n = 2), ilium (n = 2), humerus (n = 2), ulna (n = 1), wrist (n = 1), knee joint (n = 1), femur (n = 2), tibia (n = 1), toe (n = 1), and kidney (n = 1). In the initial examination, 11 patients were misdiagnosed, which delayed the final diagnosis in 7 patients. Six patients received chemotherapy with rifampicin, ethambutol, and clarithromycin, and 8 patients received other macrolide-based therapy. Five patients underwent surgical treatments in former hospitals, and 8 patients underwent surgical treatments (including salvage surgeries) in our hospital. With regard to outcome, 9 patients achieved healing, 2 patients with relapse were healed after retreatment, 1 patient was undergoing treatment, 1 patient had interrupted treatment, and 1 patient died during the treatment period.

Discussion: Osteoarticular NTM infection presented widely spread lesions in the spine and other various locations, mostly developed as a part of disseminated infection. Most patients were aged or immunosuppressed, but some patients were healthy individuals with no relevant medical history. Thus, if a patient is diagnosed with disseminated NTM infection, examination for possible lesions in other sites, including the bone and joint, should be performed. Cutaneous lesions, including subcutaneous abscess, were also characteristic. It is worth mentioning that such lesions can develop even under chemotherapy. Given the increasing trend in the overall incidence of NTM infection, awareness that NTM is a causative organism of osteoarticular infection is important.