Objective: To test the hypothesis of increased frequency of HLA-B35 in self-limiting, unclassified rheumatism (SUR).
Methods: Patients (n = 50) were included if they had swelling of one or more joints for more than 24 h and/or pain without trauma of 2 or more joints for one month or longer, and at least one of (1) history of joint swelling, (2) morning stiffness, (3) elevated erythrocyte sedimentation rate and/or C-reactive protein. Patients fulfilling diagnostic criteria sets of any rheumatic disease and patients with other identified diseases were excluded. Controls were 50 patients with rheumatoid arthritis (RA) and 199 healthy blood donors.
Results: HLA-B35 frequency (0.32) was significantly greater in SUR than in RA (0.14) and controls (0.17). HLA-DR4 frequency was significantly increased in HLA-B35 positive SUR, while that of HLA-DR1 was decreased (NS). Clinical characteristics of SUR were: history of atopy; transient, mono or oligoarticular synovitis and widespread, longlasting pain. HLA-B35 positive patients with SUR more often had hip, knee, or back pain than HLA-B35 negative patients.
Conclusion: HLA-B35 frequency is increased in SUR, while HLA-DR1 frequency is not. A likely hypothesis of attenuated immune inflammation in SUR is further supported by results in juvenile RA, adult Still's disease, and a series of mild inflammatory arthritides, and by indirect evidence of decreased Th1 response and increased Th2 response in HLA-B35 positive patients with various conditions.