Autoinflammatory diseases (AID) are clinical entities characterized by recurrent inflammatory attacks in absence of infection, neoplasm or deregulation of the adaptive immune system. Among them, hereditary periodic syndromes, also known as monogenic AID, represent the prototype of this disease group, caused by mutations in genes involved in the regulation of innate immunity, inflammation and cell death. Based on recent experimental acquisitions in the field of monogenic AID, several immunologic disorders have been reclassified as polygenic/multifactorial AID, sharing pathogenetic and clinical features with hereditary periodic fevers. This has paved the way to new treatment targets for patients suffering from rare diseases of unknown origin, including Behçet's disease, Still disease, Schnitzler's disease, PFAPA (periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis) syndrome, chronic recurrent multifocal osteomyelitis (CRMO), non-infectious uveitis and scleritis. Gathering information on such rare conditions is made difficult by the small number of patients, along with the difficulty of obtaining an accurate diagnosis in non-specialized clinical settings. In this context, the AIDA project promotes international collaboration among clinical centres to develop a permanent registry aimed at collecting demographic, genetic, clinical and therapeutic data of patients affected by monogenic and polygenic AID, in order to expand the current knowledge of these rare conditions.