Diffuse Idiopathic Skeletal Hyperostosis

Widespread calcification and ossification of the anterolateral ligaments of the spine, which may give rise to ankylosis.

The incidence is about 0.5%/year in elderly patients. The male/female distribution is 2:1.

Widespread calcification and ossification of the anterolateral ligaments of the spine are characteristic and may result in bony ankylosis. Peripheral joints may also be involved, with evidence of osteophyte or spur formation and ligamentous calcification (enthesopathy).

The pathogenesis is unknown. Some studies have found a possible link to increases in the plasma concentrations of insulin and growth hormone. Others have postulated a relationship to increases in the concentration of vitamin A and retinoic acid derivatives; this finding is interesting because the x-ray abnormalities of diffuse idiopathic skeletal hyperostosis (DISH) resemble those of chronic hypervitaminosis A.

Symptoms, Signs, and Diagnosis

Typically, patients report stiffness and pain (usually mild) localized mainly to the thoracic spine. Pain may be noted years before x-ray manifestations appear. In about 15% of patients, cervical spine involvement leads to dysphagia. More than one third of patients exhibit peripheral joint manifestations; the most commonly involved sites are the heels (characterized by spur formation), elbows, knees, and shoulders. Spinal stenosis and neurologic manifestations are uncommon.

Physical examination shows few abnormalities. Thoracolumbar and cervical spine mobility may be mildly or moderately decreased, and tenderness may be present over the thoracic spine. Occasionally, anterior cervical osteophytes can be palpated at the posterior aspect of the pharynx. Laboratory findings are usually normal; about 40% of patients have asymptomatic hyperglycemia or overt diabetes mellitus.

Early in the disease, x-rays of the peripheral joints may suggest DISH, but x-rays of the spine may show normal findings. Later in the disease, rheumatic abnormalities are extensive, but pain is often minimal and spinal motion is only moderately limited. X-rays of the peripheral joints show new bone formation (whiskering) and large bone spurs, particularly on the calcaneus and olecranon process. Advanced ligamentous calcification can be seen in the iliolumbar and patellar ligaments. Periarticular osteophytes are usually conspicuous. X-rays of the spine typically show flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies, preservation of disk height, and the absence of marginal sclerosis and apophysial joint ankylosis.

Treatment

Treatment is symptomatic; physical therapy, massage, and nonopioid analgesics may be sufficient. Painful spurs may be managed by orthotics or local corticosteroid injections. Patients should be reassured that DISH does not cause permanent disability.