Objectives: To determine whether patients with ankylosing spondylitis (AS) and discitis exhibit specific characteristics as compared to patients who have AS without discitis.
Methods: We retrospectively collected clinical, laboratory, and imaging data from the charts of 79 patients with AS admitted to a rheumatology department.
Results: Of the 79 patients, 14 (18%) had discitis that was not due to infection or trauma. Mean age at the diagnosis of AS was 40 years and mean duration of AS at admission was 10 years, with no difference between the two groups. In three patients, discitis was the inaugural manifestation of AS. Two patients had discitis at two levels. The lumbar and thoracolumbar segments were the most common sites of discitis. Symptoms of discitis were present in 10 of the 14 patients. Stage III sacroiliitis was significantly more common in the patients with discitis. None of the patients experienced neurological compromise.
Conclusion: The frequency of aseptic discitis in patients with AS is probably overestimated as a result of inclusion and exclusion biases. Discitis usually occurs at an advanced stage of AS under the form of an erosive condition related to both mechanical factors and osteoporosis. Inaugural or early discitis can occur, however, as a result of the inflammatory process.