Approximately 90% of nontuberculous mycobacterium (NTM) infections involve the pulmonary system; NTM infections involving areas of the musculoskeletal system such as the joints or spine are uncommon. This report describes a case of refractory knee swelling in a patient with systemic lupus erythematosus (SLE). Indolent arthritis of the knee eventually progressed to spondylitis and a paraspinal abscess requiring surgical incision and drainage. The cause of the infectious arthritis and spondylitis was diagnosed as NTM infection, specifically Mycobacterium kansasii. This case emphasizes the importance of a high index of clinical suspicion for mycobacterial infection, as well as repeated attempts to isolate the organism, in patients with SLE who present with atypical chronic arthritis.
Abscess ; Arthritis* ; Arthritis, Infectious ; Drainage ; Humans ; Joints ; Knee ; Lupus Erythematosus, Systemic ; Musculoskeletal System ; Mycobacterium kansasii ; Nontuberculous Mycobacteria* ; Spine ; Spondylitis*

Background/Aims: The association between symptomatic knee osteoarthritis (OA) and higher cardiovascular disease (CVD) mortality is established; however, findings from studies that utilized regression analysis were limited, attributed to the strong association between OA and metabolic risk factors. This study aimed to evaluate the association between knee OA and mortality through propensity score matching. Methods: This was a cohort study including Korean National Health and Nutrition Examination Survey (2010–2013) participants aged ≥ 50 years. By linking the survey data to cause of death data (through 2019) from Statistics Korea, mortality and cause-specific mortality data were obtained. Radiographic knee OA (ROA) was defined as bilateral Kellgren–Lawrence grade ≥ 2. Propensity score matching (1:1) was conducted between asymptomatic ROA, knee pain, and symptomatic ROA groups and normal groups, balancing the confounding factors. Time to death was analyzed using Cox proportional hazard modeling. Results: A higher CVD mortality was observed in the symptomatic ROA group, but not in others; the risk estimates were asymptomatic ROA (hazard ratio [HR] 1.12; 95% confidence interval [CI] 0.77–1.65), knee pain (HR 0.61; 95% CI 0.27–1.38), and symptomatic ROA (HR 1.39; 95% CI 0.89–2.17). No association was found between the all-cause/cancer mortality and other groups. Conclusions When propensity score matching controls metabolic risk factor imbalances, the association between symptomatic knee OA and higher CVD mortality was weaker compared to results of prior studies that used regression adjustment. The results may be more precise estimates of the total risk of knee OA for mortality in Koreans.