[Incorrect diagnosis of peripheral arthritis in ankylosing spondylitis]

We present a case of female patient who's been treated 28 years, under the diagnosis of rheumatoid arthritis because of the symmetric polyarthritis. After 28 years radiography of sacro-iliac joints and thoracolumbar vertebra was taken and showed changes typical for ankylosing spondylitis with asymmetrical affection of peripheral joints and with irreversible changes only in knees joints. Rheumatoid factor in serum was always negative, and the patient has also an iridocyclitis. We conclude that the diagnosis is surely ankylosing spondilitis.