The onset of ankylosing spondylitis is relatively insidious. Early on, it can manifest itself as peripheral joint pain that gradually progresses to hip, hip, lower back, intermittent dull pain with stiffness or accompanied by sciatica. The disease may be prolonged for months or years and then suddenly develop persistent pain or even more severe pain. Patients often have morning stiffness when they wake up, and the symptoms may worsen in cold and wet weather and during exertion and colds. Some patients may also have unexplained iritis, generalized fatigue, anorexia, weight loss, and hypothermia. The most common cause of ankylosing spondylitis is in men, with a male to female ratio of about 5:1. With the improvement of diagnosis, more patients with mild disease are diagnosed early. 80% of patients develop the disease before the age of 30, and less than 5% develop it after the age of 45.