To determine onset subtypes and HLA associations of juvenile rheumatoid arthritis (JRA) in a First Nations (aboriginal) population; to determine whether population frequencies of HLA antigens may explain the distribution of subtypes of JRA in this population.
All patients were children from Manitoba and Northwestern Ontario seen in a single pediatric rheumatology clinic between 1975 and 1996. Patients were identified from a clinic registry. Controls were adults of Algonkian Cree and Ojibway heritage. Class I and II major histocompatibility (HLA) typing was performed for First Nations patients and controls.
There were a total of 74 First Nations patients with JRA. The relative frequency of rheumatoid factor (RF) positive polyarticular JRA was higher and that of pauciarticular JRA was lower in First Nations compared with Caucasian patients (42 versus 3% and 22 versus 58%, respectively; p = 0.00000). HLA-DRB1*04 (63%), 08 (43%), and 1402 (25%) were the most common DRB1 antigens among controls. The main subtypes of DRB1*04 were 0404 (33% of controls) and 0407 (23%). HLA typing was 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 polyarticular JRA (n = 16) had HLA-DRB1 antigens bearing the rheumatoid arthritis (RA) shared epitope (OR 1.16, 95% CI: 0.38, 3.48). The OR for polyarticular RF positive JRA in those with DRB1*0802 and 0901 were 0.15, 95% CI: 0.02; and 1.24 and 5.83, 95% CI: 1.58, 28.38, respectively.
There was a high frequency of the RA shared epitope represented by both HLA-DRB1*0404 and 1402 in this Algonkian population. This high frequency may explain the high frequency of RF positive polyarticular JRA. DRB1*0802 may be protective, whereas DRB1*0901 may increase the risk for this subtype of JRA.