Ulcerative colitis (UC) and Crohn's disease are inflammatory bowel diseases often associated with extra-intestinal manifestations. Of these, neutrophilic dermatoses and arthropathies are the more frequently observed, while the occurrence of striated muscle disorders, namely, myositis, has been very rarely diagnosed in these kinds of patients. The coexistence of immuno-mediated diseases in patients with inflammatory bowel diseases and myositis suggests a common aetiopathogenetic mechanism underlying these conditions. The present report refers to a rare case of a 51-year-old female with UC and Hashimoto's thyroiditis who developed myositis.