Patients with a deficiency in adenosine deaminase 2 (ADA2) due to biallelic loss-of-function mutations in CECR1 display varying immunodeficiency mainly associated with hypogammaglobulinemia but also early-onset polyarteritis nodosa.155,156 The severity of polyarteritis nodosa in those patients ranges from cutaneous vasculitis to organ involvement, including early-onset and/or recurrent strokes. This evidence concerns the gene ADA2 and immune system disorder.