[Paget's disease: errors to be avoided].

Paget's disease of bone occurs in elderly people and resembles no other disease. The most frequent diagnostic errors are made when it is discovered in young adults, especially after an injury. Forms with osteolysis of the lower limbs are the most misleading, and it is better to avoid biopsies in such cases, as they may be followed by fractures. In geriatric pathology the failure to recognize that cerebral, spinal cord and cardiac manifestations are due to a specific vascular disorder of pagetic origin is a serious error as it deprives the patient of calcitonin which is the only effective therapy. Errors in the interpretation of laboratory results are easily avoided if a low hydroxyproline diet is prescribed during the week that precedes the tests. The biochemical activity should be correlated with the pagetic bone mass. Histology may wrongly suggest primary hyperparathyroidism, but patients with Paget's disease have no hypercalcaemia unless they are bedridden. Treatment relies on calcitonin and/or disodium etidronate (EHDP). Only 50% of the patients require this treatment the indications of which must carefully be weighed. EHDP may have adverse effects on bones, including fractures and pseudosarcomatous osteolysis, notably when it is given in high doses or for limited and/or osteolytic lesions. Pre and post-operative calcitonin therapy is recommended in patients undergoing surgery.