These are stimulators of interferon genes (STING)-associated vasculopathy of infancy (SAVI), which is a monogenic defect associated with excessive activity in interferon alpha and deficiency of adenosine deaminase 2, which is characterized by a polyarteritis nodosa-like picture.
Deficiency of adenosine deaminase 2 can present with a polyarteritis nodosa (PAN)-like picture and should be included in the differential of all pediatric cases of PAN with a family history or in cases with early stroke, or in cases resistant to conventional therapy.
Genetic screening and measurement of plasma levels of adenosine deaminase 2 should be considered for patients with uncommon systemic polyarteritis nodosa or early-onset cutaneous polyarteritis nodosa.
Additionally, although 'classic' PAN is not an inherited disease, mutations in specific genes, such as ADA2 (also known as CECR1), can result in a necrotizing vasculopathy similar to PAN.
Subjects with ADA2 deficiency (with or without symptoms) also had lower ADA2 enzyme activity compared to healthy pediatric controls (P < 0.0001) and patients with sporadic (nonfamilial) childhood polyarteritis nodosa (PAN) without CECR1 mutation (P = 0.0108).
Adenosine deaminase 2 (ADA2) deficiency due to CECR1 mutations is a recently defined disorder that involves systemic inflammation and vasculopathy often associated with polyarteritis nodosa.
Recessive loss-of-function mutations of ADA2, a growth factor that is the major extracellular adenosine deaminase, can cause polyarteritis nodosa vasculopathy with highly varied clinical expression.