To confirm the reported strong association between the HLA-DRB1*0401/0404 genotype and susceptibility to rheumatoid arthritis (RA), and to investigate the influence of sex, age at disease onset, and variables of disease severity on the strength of this association.
A case control design was adopted comparing the frequency of specific HLA-DRB1 genotypes between 201 Caucasian patients with RA and 139 controls. HLA typing was performed using a polymerase chain reaction based oligonucleotide approach with HLA-DR4 subtyping using an amplification refractory mutation system RFLP technique.
The risk of RA in those carrying a single shared epitope (SE) allele was 4 times, and in those carrying 2 SE alleles, 8 times that in the SE negative individuals. This increase was highest in individuals carrying 2 different SE alleles, with the risk in *0401/*0404 cases being 26 times higher. This genotype was associated with a 90-fold increased risk in men and this was more than doubled when age at disease onset was below 30. In all patients with RA, this genotype was associated with a substantially increased risk of being rheumatoid factor positive and having subcutaneous nodules and/or radiological erosion.
Possession of the HLA-DRB1*0401/*0404 genotype carries a substantially high risk for RA development specifically in its more severe forms. The risks are particularly increased in young men.