Dissection of the genetic basis of Aicardi–Goutières syndrome has highlighted a fundamental link between nucleic acid metabolism, innate immune sensors and type I interferon induction. This had led to the concept of the human interferonopathies as a broader set of Mendelian disorders in which a constitutive upregulation of type I interferon activity directly relates to disease pathology. Here, we discuss the molecular and cellular basis of the interferonopathies, their categorization, future treatment strategies and the insights they provide into normal physiology.