[Periodic fever].

Periodic fever can be defined as recurrent episodes of fever lasting from a few days to several weeks separated by symptom-free intervals of variable duration, recurring throughout several months. Although these clinical pictures are unusual in clinical practice, in some instances the differential diagnosis with recurrent infections, malignancies and connective tissue diseases is difficult. The aim of this review is to group together these different clinical pictures, which are dispersed in the literature, to obtain an overall and detailed perspective.We classified these processes in two categories: hereditary (familial Mediterranean fever, hyper-IgD syndrome, tumor necrosis factor-receptor-associated periodic syndrome, Muckle-Wells syndrome and familial cold urticaria) and non-hereditary (periodic fever, aphthous stomatitis, pharyngitis, and adenopathy syndrome [PFAPA syndrome], cyclic neutropenia, chronic infantile neurological cutaneous and articular syndrome [CINCA syndrome], Castleman's disease, early onset sarcoidosis and Blau syndrome). Although diagnosis is essentially clinical, in recent years many advances have been made in the knowledge of the molecular and genetic bases of hereditary diseases, which may be of considerable help in establishing the diagnosis and improving treatment.