Polyarteritis Nodosa

 

• Belongs to a group of diseases characterised by necrotizing inflammation of the walls of blood vessels
• Immune mediated
• Affects small and medium sized muscular arteries (not arterioles, capillaries or venules)
• Clinical manifestations result from ischaemia and infarction of the affected tissue and organs

 

Morphology

• Occurs as segmental transmural necrotising inflammation
• Most commonly affects kidney, heart, liver and GIT
• Rarely affects the lung
• Often affects vessel branchings and bifurcations
• Segmental erosion may occur resulting in vessel weakness. This may cause aneurismal dilations or ruptures
• Areas supplied by affected vessels may undergo ulceration, infarcts, ischaemic atropy or haemorrhage
• Histology of acute phase show transmural inflammation with neutrophils, eosinophils, mononuclear cells and is frequently accompanied by fibrinoid necrosis
• Vessel lumen may become thrombosed
• Later the acute inflammatory infiltrate is replaced with fibrous thickening of the vessel wall that may extend into the adventitia
• Particularly characteristic of PAN is that all stages of activity may coexist in different vessels or even within the same vessel

 

Clinical Course

• Generally a disease of young adults

• Course may be remitting and episodic
• Most common clinical manifestations are;
  • Malaise
  • Fever of unknown origin
  • Weight loss
  • Hypertension
  • Abdominal pain and melena
  • Diffuse muscular aches and pains
  • Peripheral neuritis – predominantly motor
• No glomerulonephritis (no small vessel disease)
• No association with ANCA
• Renal arterial involvement is the most common cause of death
• Therapy with corticosteroids or cyclophosphamide results in remission/cure in 90% of cases