Polyarteritis nodosa - Emerging treatments

Intravenous immunoglobulin (IVIG)

Case studies report the use of intravenous immunoglobulin (IVIG) in patients with non-HBV (hepatitis B virus)-related polyarteritis nodosa (PAN) who do not respond to conventional therapy.[86][87][88] There are also reports that IVIG can be used as a corticosteroid-sparing agent in less severe disease.[89][90] One case report demonstrated a good response with IVIG in a corticosteroid-resistant patient with HBV-related PAN.[91]

Tumour necrosis factor (TNF)-alpha antagonists

TNF-alpha antagonists are the gold standard of therapy in patients with DADA2.[92] Case studies suggest that patients with resistant PAN may respond to infliximab.[93] Some of these historic treatment refractory patients may have had DADA2. The use of etanercept in idiopathic PAN is not recommended on the basis of the findings of a study in granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis).[94]

B-cell therapy

Rituximab is a chimeric monoclonal antibody specific for human CD20-positive B lymphocytes. In patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, one trial showed that rituximab was non-inferior to oral daily cyclophosphamide for induction of remission.[95] A subsequent trial showed that regular low dose rituximab is superior to azathioprine for the maintenance of remission in patients with ANCA-associated vasculitis.[96] There have been no clinical trials with PAN, but there are a few case reports of patients with classical (non-HBV related) PAN refractory to standard therapies whom have subsequently had a good clinical response with rituximab.[97][98][99] Rituximab, especially when used concomitantly with corticosteroids, can lead to the reactivation of HBV in those who have had previous HBV infection and 'clearance' (i.e., surface and core antibody positive). There are case reports of fulminant hepatic failure in this context, and prophylactic antiviral therapy needs to be given with rituximab. Rituximab should not be used in the context of current HBV infection.[100]

Interferon alfa

In mild or moderate HBV-related PAN that is resistant to standard therapy, the addition of interferon alfa to the standard therapy has been described in case studies.[26][101]

High-dose immunosuppression with corticosteroids and cyclophosphamide in HBV-related PAN

In critically ill patients with HBV-related PAN who have uncontrolled vasculitis, one option may be to consider a course of high-dose immunosuppression with corticosteroids and cyclophosphamide. However, this approach carries the risk of promoting the underlying HBV infection, so the course should be as short as possible and accompanied by lamivudine prophylaxis.[84]