Diffuse Idiopathic Skeletal Hyperostosis: Addressing Confusion with Ankylosing Spondylitis/Spondyloarthropathy

Diffuse idiopathic skeletal hyperostosis (DISH) is an idiopathic florid enthesial reaction, especially recognized in the presence of ossification of the anterior longitudinal ligament of the spine. It is essentially an asymptomatic phenomena, rather than a disease. DISH, however, is not the only phenomenon responsible for florid enthesial reaction and recognition of such reaction, and it is important to assure that hypervitaminosis A (idiopathic or iatrogenic) or spondyloarthropathy is not actually responsible for the ossification. The paravertebral ossification in DISH is separate in space from the vertebral body, allowing it to be distinguished from the syndesmophytes of spondyloarthropathy, which produce anulus fibrosis ossification. The presence of erosion and fusion of zygapophyseal and costovertebral joints in spondyloarthropathy also facilitates distinguishing between the two phenomena. One seeks abnormalities on X-rays in attempting to explain the source of a patient’s back pain. It is critical however to determine whether a given radiologic finding (e.g., DISH) actually could be responsible. In the case of DISH, it is not and its recognition should not deter the healthcare provider from pursuing a complete evaluation.