Effects of retinoids in bone.

Skeletal effects of retinoids on the spine were studied in two clinical trials. In the first study, spinal radiographs of 96 patients who had been treated with isotretinoin for 4 to 9 months were reviewed. The average age of these patients was 25 years, and during treatment or within 2 1/2 years after the end of treatment, 26% of the patients showed progressive formation of small bony spurs consisting of tiny horizontal excrescences that arose at the anterior margin of one or more vertebral bodies adjacent to the intervertebral disk. In a second study, the radiographs of 241 patients with psoriasis who were treated continually for 1 to 2 years with acitretin were examined. Many of these patients had abnormal radiographs at the start of therapy. These preexisting conditions included psoriatic arthritis, degenerative arthritis, and diffuse idiopathic skeletal hyperostosis. Five percent of the patients showed progression of their abnormalities during the study. The difference in the rate of spur formation in the two groups may be due to multiple factors and not simply to retinoid therapy. Because of the extensive amount of preexisting disease in the psoriasis group compared with the relatively normal appearance of the spine in the isotretinoin group, the underlying disease process may be more important than the retinoid therapy. The development of the spinal spurs was not associated with specific clinical symptoms. Since there was no control group, it is unknown whether the spurs would have developed or progressed in the absence of retinoid therapy.