Type I interferons mediate immune defense against viral infections. The induction of type I interferons has stimulating and modulating effects on the innate and adaptive immune systems thereby reducing tolerance against self-antigens. Genetic defects that result in an inadequate activation of the type I interferon system can cause a group of inflammatory disorders, which are collectively referred to as type I interferonopathies. While the clinical spectrum of type I interferonopathies is broad and heterogeneous, neurological and cutaneous symptoms are the most frequent manifestations. Some clinical and genetic features of type I interferonopathies are shared by multifactorial diseases, such as systemic lupus erythematosus and systemic vasculitis. Advances in understanding the disease mechanisms underlying type I interferonopathies have pinpointed novel targets for therapeutic interventions.