The challenge of managing patients with polyarteritis nodosa

Purpose of review In this short review we focus on the problems faced by clinicians caused by the changing definitions of polyarteritis nodosa. Recent findings the term polyarteritis nodosa has been used for more than 100 years as a diagnostic term for patients with systemic vasculitis, however, specific vasculitides have been singled out like branches being chopped off a tree. Now, so little is left of the trunk of that tree that it is questionable to what extent we can trust older literature with respect to clinical features, natural history and response to treatment. Many authors of case reports, as well as authors of reviews and book chapters, claim they adhere to the Chapel Hill Consensus Conference definition of polyartentis nodosa yet still cite almost exclusively studies using older definitions without highlighting this dilemma. In the past year, two proposals affecting classification have been published: one stating that cutaneous polyarteritis nodosa and hepatitis associated polyarteritis nodosa, and one providing an algorithm to separate microscopic polyangiitis from classical polyarteritis nodosa. Summary There is hope that a wide acceptance of the new classification principles will lead to a more uniform way to diagnose classical polyarteritis nodosa, which will facilitate clinical studies and eventually improve management.