The gradual identification of genetic vasculopathies that may have been ‘misdiagnosed’ as vasculitis (with mutations in adenosine deaminase 2 or in the gene encoding stimulator of interferon genes being the two most recently described entities) may reveal new pathways in the pathogenesis of inflammatory vascular disorders that can also justify changes in their grouping and treatments [51, 52, 113]. The gene discussed is ADA2; the disease is vasculitis.