title: Similarities and differences between primary and secondary Sjögren's syndrome.
abstract: OBJECTIVE
  To define the clinical, serological, and histopathological characteristics of primary (pSS) and secondary Sjögren's syndrome (SS).
  
  
  METHODS
  Fifty subjects with pSS and 300 with connective tissue diseases (CTD; systemic lupus erythematosus 100, rheumatoid arthritis 100, scleroderma 100) were selected randomly from our patient registry. Selected patients were assessed for fulfillment of the American-European Consensus Group criteria for SS using a 3-phase approach: screening (European questionnaire, Schirmer-I test, wafer test), confirmatory (fluorescein staining test, nonstimulated whole salivary flow, anti-Ro/La antibodies), and lip biopsy (H&E and immunohistochemical staining for anti-CD20 and anti-CD45RO scored by morphometry).
  
  
  RESULTS
  All patients with pSS and 65 with CTD met criteria for SS. Oral symptoms (pSS = 92% and secondary SS = 84%; p = 0.02), parotid enlargement (pSS 56%, secondary SS 9.2%; p < 0.001), and higher prevalence (pSS 82%, secondary SS 41%; p < 0.001) and titers of anti-Ro/La antibodies were more common in pSS. Extraglandular manifestations were similar in both groups, except for Raynaud's phenomenon, which was more common in those with secondary SS (pSS 16% vs secondary SS 41%; p = 0.001). These results remained after 3 different sensitivity analyses. The prevalence of focal infiltration was also similar in both SS varieties; however, a higher B:T cell ratio and higher expression of CD20 cells (2922 vs 607.5 positive cells; p < 0.001) were observed in pSS.
  
  
  CONCLUSIONS
  A higher frequency of oral symptoms and parotid enlargement and stronger B cell activity (autoantibody production and lymphocyte infiltration) were observed in pSS. Whether these results reflect a true difference between the 2 disease entities or derive from underlying variables remains uncertain.
authors.affiliation: Department of Immunology and Rheumatology, Ophthalmology Service, and Dental Service, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México City, México.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Hernández-Molina
authors.forename: Carmen
authors.initials: C
authors.lastname: Avila-Casado
authors.forename: Francisco
authors.initials: F
authors.lastname: Cárdenas-Velázquez
authors.forename: Carlos
authors.initials: C
authors.lastname: Hernández-Hernández
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Calderillo
authors.forename: Verónica
authors.initials: V
authors.lastname: Marroquín
authors.forename: Virgilia
authors.initials: V
authors.lastname: Soto-Abraham
authors.forename: Claudia
authors.initials: C
authors.lastname: Recillas-Gispert
authors.forename: Jorge
authors.initials: J
authors.lastname: Sánchez-Guerrero
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000276:immunology; D003240:Connective Tissue Diseases / Q000175:diagnosis / Q000276:immunology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D012042:Registries; D012720:Severity of Illness Index; D012859:Sjogren's Syndrome / Q000145:classification* / Q000175:diagnosis* / Q000276:immunology; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires
chemical_list: D001323:Autoantibodies