The concept of grouping Mendelian disorders associated with an upregulation of type I interferon is not currently recognized in the medical literature. Here, we argue that such a concept has scientific validity and clinical utility. Specifically, we discuss a group of conditions, including Aicardi–Goutières syndrome, spondyloenchondrodysplasia, and cases of systemic lupus erythematosus with complement deficiency, in which an upregulation of type I interferons is apparently central to their pathogenesis. We believe that these diseases can usefully be considered to represent a novel set of inborn errors of immunity, and that the recognition of such diseases as type I interferonopathies will have significance in the development and use of targeted therapies.