Ossification of the paravertebral ligaments: a frequent complication of hypoparathyroidism.

Various forms of paravertebral ligamentous ossification (PVLO) were detected radiologically in 9 (53%) of 17 consecutive patients with hypoparathyroidism. A significant correlation was found between the period during which the patient was untreated and the incidence of ossification. Serum levels of calcium, phosphate, and their ionic product appeared not to influence the incidence. All the patients with PVLO exhibited evidence of ectopic calcification. The fact that ectopic ossification, which is histologically distinct from ectopic calcification, is frequently associated with hypoparathyroidism suggests that similar pathogenetic mechanisms are responsible for the development of these two conditions. The high incidence of PVLO in hypoparathyroid patients in this study may explain some of the neurologic findings in hypoparathyroidism that have been hard to explain simply on the basis of altered neuromuscular excitability.