title: Sarcoid arthritis: clinical characteristics, diagnostic aspects, and risk factors.
abstract: OBJECTIVE
  (a) To describe the clinical characteristics of acute sarcoid arthritis and the diagnostic value of its presenting clinical features; (b) to evaluate whether disease onset is seasonal; and (c) to evaluate whether smoking behaviour or the presence of HLA class II alleles is a risk factor for the disease.
  
  
  METHODS
  579 consecutive patients with recent onset arthritis who had been newly referred to a rheumatology outpatient clinic were included in a prospective cohort study. The presenting clinical features, the smoking behaviour, and the results of HLA-DQ and HLA-DR DNA typing of 55 patients with sarcoid arthritis, 524 patients with other arthritides of recent onset, and samples of the normal population were compared.
  
  
  RESULTS
  In all cases the disease showed a self limiting arthritis and overall good prognosis. The diagnostic ability of a combination of four clinical features--symmetrical ankle arthritis, symptoms of less than two months, age below 40 years, and erythema nodosum--was exceptionally high. When test positivity is defined as the presence of at least three of four criteria the set rendered a sensitivity of 93%, a specificity of 99%, a positive predictive value of 75%, and a negative predictive value of 99.7%. The disease clustered in the months March-July. The disease was negatively associated with smoking (odds ratio (OR) 0.09; 95% confidence interval (95% CI) 0.02 to 0.37) and positively associated with the presence of the DQ2 (DQB1*0201)-DR3 (DRB1*0301) haplotype (OR 12.33; 95% CI 5.97 to 25.48).
  
  
  CONCLUSIONS
  The disease entity acute sarcoid arthritis has highly diagnostic clinical features. The seasonal clustering, the protective effect of smoking, and the association with specific HLA class II antigens support the hypothesis that it results from exposure of susceptible hosts to environmental agents through the lungs.
authors: Department of Rheumatology, Leiden University Medical Centre, Leiden, The Netherlands. F.C.Breedvel@LUMC.nl
authors: H
authors: H
authors: Visser
authors: K
authors: K
authors: Vos
authors: E
authors: E
authors: Zanelli
authors: W
authors: W
authors: Verduyn
authors: G M Th
authors: GM
authors: Schreuder
authors: I
authors: I
authors: Speyer
authors: F C
authors: FC
authors: Breedveld
authors: J M W
authors: JM
authors: Hazes
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D001168:Arthritis / Q000175:diagnosis* / Q000188:drug therapy / Q000209:etiology; D015331:Cohort Studies; D005260:Female; D006683:HLA-DQ Antigens / Q000235:genetics; D015803:HLA-DR3 Antigen / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012507:Sarcoidosis / Q000175:diagnosis* / Q000188:drug therapy / Q000209:etiology; D012621:Seasons; D012907:Smoking / Q000009:adverse effects
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D006683:HLA-DQ Antigens; C053186:HLA-DQ2 antigen; D015803:HLA-DR3 Antigen