Similarity between chronic reactive arthritis and ankylosing spondylitis.A 32-35-year follow-up study.

Objective: We assessed the long-term outcome of recent reactive arthritis (ReA) during 1973-2007 and ankylosing spondylitis (AS) during 1973-1997 to identify similarities in manifestations of disease.

Methods: Radiographs of the sacroiliac, hand and foot joints were taken at onset and at 8, 20, and in ReA 32 years from entry among recent-onset (<6 months) patients; 60 with ReA and 17 with AS. Sacroiliacal joints using the modified New York 1984 criteria and the Larsen score of 0-100 of 20 joints of hands and feet were assessed. The number of swollen joints, patients with orthopaedic operations or iritis or HLA-B27 or retirement because of spondyloarthritis, and ESR were recorded.

Results: The onset age of 60 ReA patients (34 men) was 17-54 years, mean 32 (SD 10) and 51 (85%) were HLA-B27 positive. The number of onset swollen joints was 1-5, mean 2.6 (SD 1.6), while in 40 patients at the 30-year check-up it was 0-3, mean 0.2 (SD 0.6). ESR was at onset mean 55 mm/h (SD 33) and at the 30-year check-up 15 mm/h (SD 11). Yersinia enterocolitica type 3 antibodies were raised in 22 (37%) patients at onset. The end-point Larsen score was 2-6, mean 4 in 6 patients. One ankle joint arthroplasty and five smaller operations had been performed. Bilateral grade 2-3 sacroiliitis developed in 9/60 (15%), and unilateral grade 2-4 in 3. The incidence of iritis was 12/60 (20%). Erosive arthritis or iritis or sacroiliitis developed in 24/60 (40%) participants. Thirteen (22%) retired because of arthritis while five died. Of 17 AS patients (8 men), whose age was initially 21-50 years, mean 33 (SD 10), 11 (65%) had rheumatic symptoms years before our first examination. All were HLA-B27 positive and developed grade 2-4 bilateral sacroiliitis during the 20-year follow-up. The end-point Larsen score was 2-22, mean 9 (SD 8) in 5 patients. Hip arthroplasties were performed in one and small-joint operations in 3. ESR was at onset mean 54 mm/h (SD 29), and at the last measurement mean 26 mm/h (SD 21). Iritis was found in 5/17 (29%); seven (41%) retired due to AS; five died.

Conclusion: Our community-based inception cohorts show that with time, among a number of similarities most often sacroiliitis, peripheral arthritis and iritis developed in both chronic ReA and AS. These HLA-B27-related diseases would appear to be identical. The differences between patients depend on the chronicity of the sickness. The hypothesis that HLA-B27 is related to chronicity of disease seems to be valid.