Neurinomas are tumors of Schwann cells of the peripheral nerve sheath. Sacral location is rarely reported especially in spondyloarthritis patients. Herein, we report a case of uncommon pygalgia in a 25-year-old man with history of a non-radiographic axial spondyloarthritis and in whom the diagnosis of sacral neurinoma was established.

Primary synovial chondromatosis is an uncommon and benign metaplastic condition that usually affects large joints. Though shoulder involvement is scarce, and there are only a few cases in the pediatric population.