Objective: To determine the influence of HLA-DRB*1 genes on susceptibility to and severity of rheumatoid arthritis (RA) in patients with late onset compared with younger onset disease.
Methods: The clinical, biological, and HLA-DRB1 typing characteristics of two groups of patients were studied retrospectively. Group 1 consisted of 262 patients whose disease onset was before or at the age of 60 (young onset RA (YORA)). Group 2 included 60 patients whose illness began after the age of 60 (elderly onset RA (EORA)).
Results: The shared epitope level was similarly increased in both groups of patients compared with normal controls (195/262 (74%) in group 1 and 43/60 (72%) in group 2 v 645/1609 (40.1%) in controls). No differences were noted between the two groups of patients for each separate disease related allele. In contrast, when studying all HLA-DRB1*04 RA related alleles as a group, these alleles were underrepresented in EORA compared with YORA (22/60 (37%) v 135/262 (52%); odds ratio 2.0; 95% confidence interval 1.0 to 3.3). An inverse trend was seen for HLA-DRB1*01 alleles. There were no differences in biological characteristics or extra-articular manifestations between the patient groups. The differences noted in radiological evaluation or the number of prescribed disease modifying antirheumatic drugs seemed to be linked with differences in disease duration.
Conclusion: HLA-DRB1 RA related alleles influence both EORA and YORA. However, HLA-DRB1*04 RA linked alleles are not as closely associated with RA in the elderly as they are in younger patients. This suggests that the importance of these genes in the susceptibility to RA may be lower in elderly patients.