Polyarteritis Nodosa

Polyarteritis nodosa (PAN) is a medium-sized vessel primary or idiopathic systemic necrotizing vasculitis in which small vessels are not affected and anti-neutrophil cytoplasmic antibodies (ANCA) are not present. Hepatitis B virus and other viral infections may cause vascular lesions, clinically and histologically indistinguishable from PAN. Clinical manifestations of PAN are widespread and heterogeneous. Peripheral nerves and skin are the most frequently affected tissues. However, gastrointestinal tract, kidney, heart, and central nervous system involvement is associated with a worse prognosis. When biopsies of involved tissues are negative for vasculitis or cannot be obtained, visceral angiography may support the diagnosis of PAN if micro-aneurysms and/or stenotic arterial lesions are evidenced. Treatment strategies include high-dose glucocorticoids in combination with additional immunosuppressive agents in severe cases, particularly intravenous cyclophosphamide. After the 1990 American College of Rheumatology (ACR) classification criteria for PAN, the categorization of ANCA-associated vasculitides and infection-associated vasculitides as conditions different from PAN, as well as the recent discovery of monogenic autoinflammatory diseases presenting with PAN-like phenotypes, such as deficiency of adenosine deaminase 2 (DADA2) and vacuoles, E1 enzyme, X-linked, auto-inflammatory, somatic (VEXAS) syndrome, have all contributed to unveil the real rarity of PAN.