How is polyarteritis nodosa (PAN) distinguished from microscopic polyangiitis (MPA)?

Updated: Nov 14, 2017
  • Author: Dana Jacobs-Kosmin, MD, FACP; Chief Editor: Herbert S Diamond, MD  more...
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Answer

The strong association of MPA with ANCA, as well as the pathologic and clinical differences between MPA and PAN, demonstrate that PAN and MPA are likely separate disorders. It was not until 1994 that histologic criteria to distinguish PAN from MPA were defined at the international Chapel Hill Consensus Conference (CHCC). [8] According to the CHCC criteria, the presence of vasculitis in arterioles, venules, and capillaries defines the diagnosis of MPA (although small- and medium-sized arteries may also be involved in MPA) and excludes the diagnosis of PAN. (See Presentation, DDx, and Workup.)


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