title: Osteoarticular tuberculosis in patients with systemic lupus erythematosus.
abstract: BACKGROUND
  Systemic lupus erythematosus (SLE) patients are at increased risk of developing tuberculosis (TB), particularly extrapulmonary TB (ExP-TB).
  
  
  OBJECTIVE
  The present study was undertaken to investigate whether SLE patients showed increased susceptibility to develop osteoarticular TB (OA-TB).
  
  
  METHODS
  We retrospectively reviewed and compared the frequency of ExP-TB, in particular OA-TB, in patients with SLE at a tertiary hospital in South Africa, to a non-SLE control TB group seen at the same hospital.
  
  
  RESULTS
  TB was diagnosed 111 times in 97 (17%) of the 568 SLE patients. The relative frequency of ExP-TB in the SLE group (25.2%) was significantly lower than in the control group (38.5%) (OR = 1.9, P = 0.006). In contrast, OA-TB was diagnosed in the SLE group in nine (8.1%) patients (seven with peripheral arthritis and two with TB spine) compared to 54 (0.4%) in the overall control group (OR = 20.8, P < 0.001) and 13 (0.2%) in the subgroup of known HIV positive patients in the control group (OR = 44.4, P < 0.001). Within the SLE group, Black ethnicity (P = 0.003), lymphopaenia (P = 0.001), C3/C4 hypocomplementaemia (P = 0.05), corticosteroids [maximum dose (P = 0.002) and duration of treatment (P = 0.02)] and immunosuppressive agents (P = 0.02) were risk factors for TB. Duration of corticosteroid therapy was the only risk factor for OA-TB (P = 0.04).
  
  
  CONCLUSIONS
  While the relative frequency of ExP-TB was lower in the SLE group compared to the control group, our findings suggest that SLE patients are at particular risk of developing OA-TB. Further prospective studies are needed to better understand the mechanisms that predispose SLE patients to OA-TB.
authors.affiliation: Department of Medicine, Division of Rheumatology, Chris Hani Baragwanath Hospital, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: B
authors.initials: B
authors.lastname: Hodkinson
authors.forename: E
authors.initials: E
authors.lastname: Musenge
authors.forename: M
authors.initials: M
authors.lastname: Tikly
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004198:Disease Susceptibility; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications*; D008875:Middle Aged; D009894:Opportunistic Infections / Q000453:epidemiology*; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D014394:Tuberculosis, Osteoarticular / Q000453:epidemiology*; D055815:Young Adult