Current and future advances in practice: polyarteritis nodosa and related vasculitides

Polyarteritis nodosa (PAN) is a rare vasculitis affecting predominately medium-sized vessels. Our evolving understanding of PAN, including the role of HBV and discovery of monogenic variants such as deficiency of adenosine deaminase 2 (DADA2), has resulted in idiopathic PAN becoming a very rare condition with an annual incidence of 0.6-19.9/million. The investigative approach is to assess organ involvement and confirm the diagnosis either by imaging or biopsy. Conventional catheter angiography is being replaced by CT or MR angiography, which provide increasingly good resolution of the typical fusiform narrowing and aneurysm. ANCA-associated vasculitis (AAV) should be excluded. DADA2 is being more frequently identified as causing a PAN-like illness, especially in children; cases presenting in adulthood are now recognised. In children and most adults, genotyping for DADA2 should be undertaken. There are no high-quality randomised controlled trials of treatment in idiopathic PAN. Current approaches have been adapted from those used to treat other types of vasculitis. The five-factor score may be used to stratify patients to identify those needing intensive therapy with glucocorticoids combined with CYC. In order to reduce the burden of glucocorticoid toxicity, the ACR has advocated the use of immunosuppressive drugs in addition to steroids in those not initially receiving CYC. Unlike AAV, there appears to be little role for rituximab in the treatment of idiopathic PAN, although it is occasionally used as salvage therapy. HBV-associated PAN is treated with immunosuppression and antiviral therapy. There is reasonably good evidence to support the use of anti-TNF to treat DADA2.