Perrotta, F., S. Scriffignano, A. De Socio, and E. Lubrano. “Occult Axial Involvement in Patients With Psoriatic Arthritis Mutilans: A Case Report”. Reumatismo, Vol. 71, no. 2, July 2019, pp. 88-91, doi:10.4081/reumatismo.2019.1146.