Autoimmune diseases present with a wide range of symptoms able to affect nearly all body organs. Differential diagnosis of these symptoms can be difficult, as a particular presenting symptom may be encountered in distinct autoimmune diseases, and at the same time many non-rheumatic diseases may share similar clinical manifestations. In the large overlapping field of infections and rheumatology, many autoimmune diseases may present as fever of unknown origin, and on the other hand, many different infectious agents cause signs and symptoms mimicking a systemic autoimmune disease. Clinical manifestations affecting the skin and its annexes, oral cavity, joints, and periarticular structures but also major organs such as the heart and vascular system, lung, liver, spleen, and gastrointestinal tract can be initial symptoms of a systemic autoimmune disease. The use of immune checkpoint inhibitors for the treatment of different types of cancers has radically changed