Autoimmune diseases (ADs) share common mechanisms, risk factors, clinical phenotypes, and treatment. Such commonalities have been called “autoimmune tautology”. Polyautoimmunity, both overt and latent, indicates the presence of more than one AD or the presence of diverse autoantibodies in a single patient and is considered the clue for the understanding of the variability, but also similarity, among ADs. Herein, we describe the evidence of PolyA as the basis for autoimmune tautology and the implications for the development of a new taxonomy of ADs.
