Acitretin-induced enthesitis in a patient with psoriatic arthritis

A patient with psoriatic arthritis and cutaneous psoriasis took acitretin for 10 years to treat his skin lesions. Radiographs disclosed exuberant ossifications in several entheses. Their features were not typical for psoriatic arthritis but were consistent with acitretin-induced hyperostosis. Retinoids are known to induce hyperostosis, most notably when they are used in high dosages and over long periods. The concomitant presence of two conditions affecting the entheses may explain the exuberant nature of the ossifications in our patient.