Etretinate-induced heterotopic bone formation about the hip joint. A case report including ultrastructural study.

Despite considerable documentation for retinoid-induced hyperostosis, sufficient knowledge regarding its management and histologic features is not available. In a 26-year-old man with etretinate-induced heterotopic bone formation about the hip joint, the use of etidronate disodium was unsuccessful. Surgical excision of the heterotopic bone dramatically improved restricted motion of the hip joint without initiating significant postoperative heterotopic ossification. Ultrastructural study showed abundant myofibroblasts in the fibrous tissue close to the heterotopic bone. Their role in local biologic events should be determined.