Diffuse idiopathic skeletal hyperostosis and isotretinoin in cystic acne.

We present the case of a 35-year-old man with thoracic back pain and stiffness, whose only medical history was cystic acne treated with repeated courses of retinoids. His thoracic spine was severely limited in range of movement and was found, on X-ray, to have unilateral hyperostosis typical of diffuse idiopathic skeletal hyperostosis (DISH)--an often asymptomatic condition rarely found in those under 50. Back stiffness in young patients with prolonged retinoid exposure should be investigated.