Reiter's disease and ankylosing spondylitis.
D016918:Arthritis, Reactive / Q000175:diagnosis*; D005500:Follow-Up Studies; D006801:Humans; D008161:Lumbosacral Region; D011859:Radiography; D012446:Sacroiliac Joint; D013167:Spondylitis, Ankylosing / Q000175:diagnosis*