*3.2.1 Polyarteritis nodosa (PAN)*

It is a rare necrotizing systemic vasculitis that affects small- and medium-sized vessels and is not usually associated with ANCA [8, 9], although there are reports in the literature of patients with PAN and positive ANCA. Several treatments are suggested for this condition, and the control is still a challenge [9].

Cutaneous involvement and peripheral nerves are the favorite sites of the disease, cutaneous and gastrointestinal vasculitis have specific histopathological characteristics, and until now, it has no development glomerulonephritis described. Gastrointestinal tract involvement is common and is one of the predictors of disease morbidity and mortality. There is cutaneous PAN without systemic involvement, and it very rarely progresses to the systemic form of the disease. According to the new classification, PAN is subdivided into idiopathic PAN and hepatitis B-associated PAN [9].

Treatment of PAN is usually based on the combination of systemic corticosteroids and immunosuppressants. The most commonly used medications are cyclophosphamide, azathioprine, methotrexate or mycophenolate mofetil [9].

The use of biological medications is reserved for cases of refractory PAN without association with hepatitis B. The use of rituximab, an anti-CD20 monoclonal antibody, has not been formally indicated for patients with PAN, but its use is supported in patients with ANCA-associated vasculitis. There are case reports using anti-TNF-alpha, such as etanercept and infliximab, and tocilizumab, but only in refractory cases [8].
