Confusion of roentgenographic differential diagnosis between ankylosing hyperostosis (Forestier's disease) and ankylosing spondylitis

A patient with ankylosing hyperostosis (Forestier's disease) initially diagnosed elsewhere as a case of ankylosing spondylitis with bamboo spine, is presented. The characteristic roentgenographic findings of Forestier's disease in the axial skeleton of this patient are described, including computerized tomography of the lower lumbar spine and sacroiliac joints. Major clinical and radiological distinguishing features of Forestier's disease and ankylosing spondylitis are discussed.