Feels like there is an outbreak of vasculitis recently at the SFVA with a few morning reports on palpable purpura and it’s characteristic finding on pathology: leukocytoclastic vasculitis (LCV)! Remember, LCV is typically indicative of a small vessel vasculitis, but the medium vessel vasculitis PAN can present with LCV. PAN was discussed in this case in particular given the largely unrevealing serologic workup thus far (see ZSFG post on LCV w/u earlier this week!).
Polyarteritis nodosa definition: systemic necrotizing vasculitis of medium-small sized muscular arteries.
Etiology: Most cases are idiopathic, but HBV, HCV, and hairy cell leukemia are risk factors. For HBV associated PAN, the onset of disease usually occurs within 4 months of HBV infection.
Clinical features: Weight loss, malaise, fever are most common symptoms. Also included are neuropathies (mononeuritis multiplex and polyneuropathy), arthralgias, livedo reticularis, ulcers, palpable purpura, abdominal pain (mesenteric arteritis –>ask about pain after meals aka intestinal angina), stroke, orchitis (from micro-infarcts!), pericarditis, and rarely claudication, ischemia, and tissue necrosis.
Renal involvement is common (see below) on autopsy studies. Clinically, HTN, sub-nephrotic range proteinuria, mild hematuria are commonly seen. RBC casts are rare in PAN and should make you consider one of the ANCA associated vasculidities or SLE.
Making the dx: There is no diagnostic lab test for PAN, and PAN often has normal complement, cryos, ANCA, ANA that would help define other types of vasculitis. Biopsy of affected organs can show medium sized vessel inflammation. Mesenteric or renal angiography (and sometimes CT) can make the dx with the presence of multiple aneurisms!