Childhood-onset polyarteritis nodosa is an autosomal recessive systemic vascular inflammatory disorder characterized mainly by involvement of the skin, nervous system, kidney, and gastrointestinal tract. There is considerable variability in the severity and age at onset, although most patients have onset of symptoms in the first decade. Features include recurrent ischemic stroke affecting the small vessels of the brain and resulting in neurologic dysfunction, recurrent fever, elevated acute-phase proteins, myalgias, and livedo racemosa or reticularis with an inflammatory vasculitis on biopsy. Some patients develop hypertension, aneurysms, or ischemic necrosis of the digits (summary by Zhou et al., 2014 and Navon Elkan et al., 2014). Some patients present with clinical immunodeficiency (van Eyck et al., 2014). The disease or phenotype is polyarteritis nodosa, childhoood-onset (EFO_0009295, an Experimental Factor Ontology identifier). Also known as: ADA2 deficiency.