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

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.

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.

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.

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.