title: Linkage of rheumatoid arthritis with HLA.
abstract: OBJECTIVE
  To determine whether HLA exerts a variable influence on the predisposition of siblings of probands with clinically mild and severe rheumatoid arthritis (RA).
  
  
  METHODS
  Calculation of crude and adjusted odds ratios for concordance rates in sibships sharing two, one and no HLA haplotypes with a proband with clinically mild and severe RA, and HLA haplotype sharing in multiply affected sibships in the same clinical groups.
  
  
  RESULTS
  Compared with a reference value of 1.0 in siblings sharing no HLA haplotypes with a proband with mild RA, siblings sharing two HLA haplotypes with a severely affected proband had a sibship concordance rate odds ratio of 9.7 (95% confidence interval 2.5 to 38.2). When adjusted for age, sex, and disease duration, the odds ratio was 7.6 (1.8 to 32.4). No other sibships showed concordance rates which were significantly higher than the reference group. HLA haplotype sharing in multiply affected sibships in which the proband had severe RA deviated significantly from random (two, one, and no HLA haplotypes shared: 53.3, 40, and 6.7%, respectively; expected 25, 50, and 25%), whereas in sibships of probands with mild RA they did not (14.6, 70.8, and 14.6%).
  
  
  CONCLUSIONS
  In the predisposition of siblings to RA, sharing HLA haplotypes with a proband is only important if the proband has severe RA. Mild RA is not genetically linked to the HLA region.
authors.affiliation: Department of Rheumatology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.
authors.forename: C M
authors.initials: CM
authors.lastname: Deighton
authors.forename: P J
authors.initials: PJ
authors.lastname: Kelly
authors.forename: D J
authors.initials: DJ
authors.lastname: Walker
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D005190:Family; D005260:Female; D006680:HLA Antigens / Q000032:analysis / Q000235:genetics*; D006684:HLA-DR Antigens / Q000032:analysis / Q000235:genetics; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D008285:Major Histocompatibility Complex / Q000235:genetics; D008297:Male; D008875:Middle Aged
chemical_list: D006680:HLA Antigens; D006684:HLA-DR Antigens