JUVENILE RHEUMATOID-ARTHRITIS IN A CANADIAN FIRST NATIONS (ABORIGINAL) POPULATION - ONSET SUBTYPES AND HLA ASSOCIATIONS

Objective, To determine onset subtypes and HLA associations of juvenil e rheumatoid arthritis (JRA) in a First Nations (aboriginal) populatio n; to determine whether population frequencies of HLA antigens may exp lain the distribution of subtypes of JRA in this population. Methods, All patients were children from Manitoba and Northwestern Ontario seen in a single pediatric rheumatology clinic between 1975 and 1996. Pati ents were identified from a clinic registry. Controls were adults of A lgonkian Cree and Ojibway heritage. Class I and II major histocompatib ility (HLA) typing was performed for First Nations patients and contro ls. Results, There were a total of 74 First Nations patients with JRA. The relative frequency of rheumatoid factor (RF) positive polyarticul ar JRA was higher and that of pauciarticular JRA was lower in First Na tions compared with Caucasian patients (42 versus 3% and 22 versus 58% , respectively; p = 0.00000). HLA-DRB104 (63%), 08 (43%), and 1402 (2 5%) were the most common DRB1 antigens among controls. The main subtyp es of DRB104 were 0404 (33% of controls) and 0407 (23%). HLA typing w as performed for 39 First Nations patients; 27 were Cree or Ojibway, 4 were from other tribes, and 8 were part First Nations. Among Cree and Ojibway, 59% of controls and 63% of patients with RF positive polyart icular IRA (n = 16) had HLA-DRB1 antigens bearing the rheumatoid arthr itis (RA) shared epitope (OR 1.16, 95% CI: 0.38, 3.48). The OR for pol yarticular RF positive JRA in those with DRB10802 and 0901 were 0.15, 95% CI: 0.02; and 1.24 and 5.83, 95% CI: 1.58, 28.38, respectively. C onclusion, There was a high frequency of the RA shared epitope represe nted by both HLA-DRB10404 and 1402 in this Algonkian population. This high frequency may explain the high frequency of RF positive polyarti cular JRA. DRB10802 may be protective, whereas DRB1*0901 may increase the risk for this subtype of JRA.