Objective: To explore the role of HLA-DRB1 genes in determining disease severity in rheumatoid arthritis.
Design: Case series of patients with seropositive rheumatoid arthritis.
Setting: The outpatient clinic of the Division of Rheumatology, Mayo Clinic.
Patients: One hundred and two patients with seropositive, erosive rheumatoid arthritis and a minimum disease duration of 3 years.
Measurements: Patients were genotyped for both HLA-DRB1 alleles and were categorized according to the expression of one or two disease-linked HLA-DRB1 alleles. Identification of HLA-DRB1 alleles was done by the polymerase chain reaction and subsequent oligonucleotide hybridization. Homozygosity for allelic variants was confirmed by sequence analysis. Immunogenetically defined patient subgroups were retrospectively evaluated for joint destruction and patterns of disease manifestation, including rheumatoid organ disease.
Results: Of 102 patients, 98 (96%) expressed the disease-linked sequence polymorphism. Forty-seven patients (46%) carried a double dose of the relevant sequence stretch: Twenty-eight patients expressed HLA-DRB1*04 variants on both alleles, and 19 combined an HLA-DRB*04 variant with HLA-DRB1*0101 or DRB1*1402. Nodular disease was present in 100% of patients typed as HLA-DRB1*04/04 and in 59% of patients typed as HLA-DRB1*04 and who had inherited only a single dose of the disease-linked sequence polymorphism (P < 0.0001). Major organ systems were involved in 61% and 11% of these two patient groups, respectively (P < 0.0001); and joint surgery was required in 61% and 25% (P < 0.002), respectively. Patients typed as HLA-DR*04/01 had intermediate clinical courses.
Conclusion: Genotyping patients with rheumatoid arthritis for both HLA-DRB1 alleles identifies clinical subsets with distinct profiles of disease manifestations.