Palindromic rheumatism (PR) is an autoimmune related disease characterized by sudden, multiple, and recurring attacks of joint pain and swelling, typically in the hands and feet. Each episode may last from several hours to several days. The frequency of attacks also varies, from one episode a day to several during the course of a year. Between attacks, the symptoms disappear and the affected joints appear normal on x-ray exams. The cause of palindromic rheumatism is unknown, although a possible allergic origin has been suggested. There may also be a clinical association between antiphospholipid syndrome and palindromic rheumatism. Some individuals with palindromic rheumatism develop chronic joint inflammation and go on to develop rheumatoid arthritis.