<qa>  What is the first appearance of symptoms of inflammatory low back pain?Patients who developed ankylosing spondylitis after age 16 may be eligible for this study. The onset of disease is dated to the first appearance of symptoms of inflammatory low back pain or restricted spinal motion. Patients with a spondyloarthropathy other than AS may not participate. Candidates will be screened with a medical history and physical examination, blood test, and review of their medical records. They will also complete a questionnaire about their disease symptoms and medical history. 