Only weak association between disease severity and HLA-DRB 1 genes in a Swiss population of rheumatoid arthritis patients

This study analyses the prognostic value of HLA-DRB 1 genes for Swiss patients with rheumatoid arthritis (RA). HLA-DRB 1 genotyping was performed in 83 patients using the polymerase chain reaction and subsequent oligonucleotide hybridisation. They were categorised according to the presence of one or two putatively relevant genes (DRB 1^*01 and/or DRB 1^*04) and retrospectively evaluated for sex, age at disease onset, seropositivity, erosive disease and extraarticular manifestations. Sixty-one patients (73%) had disease-associated alleles. Twenty-four patients showed HLA-DRB 1^*04 variants on both alleles or combined an HLA-DRB 1^*04 variant with HLA-DRB 1^*01, while 37 patients expressed only one relevant allele. Interestingly, 22 patients did not express any relevant allele. Some 52% of patients had nodular disease, 88% were seropositive, 96% had joint erosions and I I% expressed vasculitis and/or rheumatoid organ disease. A significant difference was observed only for the number of seropositive individuals, which was slightly higher in the group of patients expressing a double dose of disease-associated alleles than in patients who had no relevant alleles. Moreover, patients expressing homozygous DRB 1 alleles had a significantly earlier onset of disease than those who were heterozygous. We conclude from these findings that HLA-DRB 1 genotyping in a Swiss population of RA patients only weakly identifies clinical subsets with distinct profiles of disease manifestations and is not of strong prognostic value to determine disease severity in individual patients.