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
- Malaise
- 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