Polyarteritis nodosa (PAN) is a systemic inflammatory necrotising vasculitis that involves small to medium sized arteries (larger than arterioles).
Polyarteritis nodosa (PAN) is commoner in males and typically presents around the 5th to 7th decades. Twenty to thirty percent of patients are hepatitis B antigen positive.
Patients can present with systemic and focal symptoms.
Non-specific systemic signs and symptoms are almost always present and include fever, malaise and weight loss.
Localised symptoms relate to ischaemia and infarction of affected tissues and organs. The most commonly involved vessels, are the renal arteries 1, with visceral involvement also considered relatively common. The pulmonary circulation is typically spared, although bronchial arteries may occasionally be involved.
Frequent sites of involvement are 3,5:
- renal: 80-90%, tends to be the prominent site and major cause of death
- cardiac: ~70%
- gastrointestinal tract: 50-70%
- hepatic: 50-60%
- spleen: 45%
- pancreas: 25-35%
- CNS complications: 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 .
- pANCA: levels can correlate with disease activity
- hepatitis B
- hepatitis C
Routine contrast enhanced CT may be entirely normal, or may demonstrate focal regions of infarction or haemorrhage in affected organs.
Angiography / CT angiography
Direct catheter angiography is far more sensitive to changes within small vessels, although a good quality CTA can also demonstrates changes. Findings include:
- multiple microaneurysms
- characteristic but not pathognomonic
- typically 2-3 mm in size but can be up to 1cm
- in the kidneys, the micro aneurysms typically involve the inter lobar and arcuate arteries
- haemorrhage may be evident due to focal rupture
- occlusion may also be evident
Treatment and prognosis
Polyarteritis nodosa is usually fatal if untreated, often as a result of progressive renal failure or gastrointestinal complications. Prompt treatment with corticosteroids and cyclophosphamide can results in remission, and a remission or cure able to be obtained in 90% of patients 3.
History and etymology
It was initially described by Kassmaul and Maier in 1866
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- 3. Ha HK, Lee SH, Rha SE et-al. Radiologic features of vasculitis involving the gastrointestinal tract. Radiographics. 20 (3): 779-94. Radiographics (full text) - Pubmed citation
- 4. Provenzale JM, Allen NB. Neuroradiologic findings in polyarteritis nodosa. AJNR Am J Neuroradiol. 17 (6): 1119-26. AJNR Am J Neuroradiol (abstract) - Pubmed citation
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