Phenotypic similarities between ADA2 deficiency (DADA2) and type I interferonopathies, such as AGS, suggest a shared pathogenic background.157 In accordance with this is the fact that DADA2 patients display a type I interferon signature correlating with disease activity, as shown in transcriptome analysis of their peripheral blood cells.157,158 The identification of DADA2 as a monogenic form of polyarteritis nodosa suggests that defects in adenosine catabolism result in inflammation by inducing the production of type I interferons. Here, ADA2 is linked to polyarteritis nodosa.