title: Familial vs sporadic rheumatoid arthritis (RA). A prospective study in an early RA inception cohort.
abstract: OBJECTIVE
  To study potential differences in demographic, process and outcome variables between familial and sporadic rheumatoid arthritis (RA) in an early RA inception cohort.
  
  
  METHODS
  In 1998, we ascertained the familial status of all collaborative patients in a large early RA inception cohort at our department. Familial RA was defined by the presence of at least two siblings fulfilling the American College of Rheumatology criteria for RA. Baseline demographic data and prospectively recorded disease activity variables, therapies and radiological damage during the first 6 yr of disease were included in the analysis. A regression analysis was performed to assess whether familial clustering is a prognostic factor.
  
  
  RESULTS
  We identified 142 patients with sporadic and 36 with familial RA. The most striking difference between these groups was the larger sibship size in multicase families (8.2 +/- 2.5 vs 5. 5 +/- 2.8; P < 0.0001). Age at onset was similar in both groups, although males with familiar RA were younger at disease onset than those with sporadic RA (median 50 vs 57 yr; P=0.03). No differences were found in gender, presence of rheumatoid factor (RF), antinuclear factor and HLA-DR typing or in disease activity, interventions and outcome over 6 yr of follow-up. Early radiological damage and disease activity, but not familial history of RA were prognostic for X-ray damage.
  
  
  CONCLUSIONS
  We show that sibship size is the only relevant risk factor for familial RA. No differences in genotypic and phenotypic characteristics, disease severity or radiological damage were observed among familial and sporadic RA. Familial history of RA is not a poor prognostic factor. This prospective study confirms previous cross-sectional findings in the Dutch population.
authors.affiliation: Department of Rheumatology, University Hospital, Nijmegen, The Netherlands.
authors.forename: T R
authors.initials: TR
authors.lastname: Radstake
authors.forename: P
authors.initials: P
authors.lastname: Barrera
authors.forename: J M
authors.initials: JM
authors.lastname: Albers
authors.forename: H L
authors.initials: HL
authors.lastname: Swinkels
authors.forename: L B
authors.initials: LB
authors.lastname: van de Putte
authors.forename: P L
authors.initials: PL
authors.lastname: van Riel
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000235:genetics* / Q000503:physiopathology / Q000628:therapy; D001175:Arthrography; D015331:Cohort Studies; D003710:Demography; D005260:Female; D020022:Genetic Predisposition to Disease; D006684:HLA-DR Antigens / Q000235:genetics; D006801:Humans; D007596:Joints / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D006684:HLA-DR Antigens