Polyarteritis nodosa

Last revised by Henry Knipe on 2 Oct 2022

Polyarteritis nodosa is a systemic inflammatory necrotizing vasculitis that involves small to medium-sized arteries (larger than arterioles). 

Polyarteritis nodosa is more common in males and typically presents around the 5th to 7th decades. 20-30% of patients are hepatitis B antigen positive.

Patients can present with systemic and/or focal symptoms.

  • systemic signs and symptoms are almost always present and are non-specific, including fever, malaise and weight loss

  • localized symptoms relate to ischemia and infarction of affected tissues and organs; the most commonly involved vessels are the renal arteries 1 while the pulmonary circulation is typically spared

Frequent sites of involvement are 3,5,6:

  • renal: 80-90%, tends to be the prominent site and major cause of morbidity (e.g. chronic kidney disease, hypertension, hemorrhage) and death

  • cardiac: ~70%

  • gastrointestinal tract: 50-70%

  • hepatic: 50-60%

  • spleen: 45%

  • pancreas: 25-35%  

  • CNS: 20-45% 4

Initially, there is transmural and necrotizing inflammation of medium-sized arteries, mostly involving part of the circumference which causes weakening of the wall leading to microaneurysm formation and subsequent focal rupture. There is a predilection for branch points. Fibrinoid necrosis of vessels promotes thrombosis of vessels followed by infarction of the tissue supplied. Fibrous thickening and mononuclear infiltration occur at a later stage. Different stages of inflammation can occur in the same vessel at different points.

Routine contrast-enhanced CT may be entirely normal or may demonstrate focal regions of infarction or hemorrhage in affected organs. 

Direct catheter angiography is far more sensitive to changes within small vessels, although a good quality CTA can also demonstrate changes. Findings include:

  • multiple microaneurysms

    • characteristic but not pathognomonic

    • typically 2-3 mm in size but can be up to 1 cm

    • in the kidneys, the microaneurysms typically involve the interlobar and arcuate arteries

  • hemorrhage may be present due to focal rupture

  • occlusion may be present

Polyarteritis nodosa is usually fatal if untreated, often as a result of progressive renal failure or gastrointestinal complications. Prompt treatment with corticosteroids and/or cyclophosphamide may result in remission, and a remission/cure can be achieved in 90% of patients 3

It was initially described by Kussmaul and Maier in 1866.

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