Polyarteritis Nodosa

Overview
  • Polyarteritis Nodosa is a suspected autoimmune disease which primarily manifests as a vasculitis. Medium to small-sized systemic arteries of any organ can be affected with sparing of large arteries, arterioles, or smaller vasculature. Additionally, the pulmonary vasculature, regardless of size, is completely spared.
Epidemiology
  • Polyarteritis Nodosa is very rare but can affect any age group.
Morphology
  • Polyarteritis Nodosa is characterized by a necrotizing inflammation of the entire vascular wall which develops in a segmental pattern. Initially, the inflammatory infiltrate is largely neutrophilic but evolves to one dominated my mononuclear cells. Fibrinoid necrosis is frequently observed which can weaken the vascular wall and thus render it prone to aneurysmal dilations and in some cases rupture, leading to hemorrhages. Additionally, thrombosis is frequently observed in involved segments which can compromise downstream blood flow. Over time, a healing phase begins which ends in fibrotic remodelling of the entire vascular wall and may worsen luminal occlusion. Importantly, lesions can affect vasculature in virtually every organ and the different morphological stages of the disease can be observed simultaneously.
Pathogenesis
  • The pathogenesis of polyarteritis nodosa in most patients is still being understood. In roughly 20% of patients, polyarteritis nodosa may be associated with chronic viral hepatitis caused by Hepatitis B Virus infection. Here, it is thought that immune complexes between HBV surface antigen and host immunoglobulins deposit in blood vessels, resulting in vasculitis (Esentially a Type III Hypersensitivity reaction). In general, no association between polyarteritis nodosa and ANCAs has been observed.
Clinical Consequences
  • Overview
    • Polyarteritis Nodosa typically presents with non-specific constitutional symptoms and paints a complex clinical picture. In some cases, organ-specific symptomology may arise due to occlusion and downstream hypoperfusion of specific vascular beds. The kidneys are the most common organ affected. In general, disease severity relapses and remits over a lifetime.
  • Organ-specific Symptomology
    • Kidney: Characteristically there is inflammation of renal arteries without glomerulonephritis which can result in hypertension
    • Heart: Involvement of coronary arteries can result in Myocardial Infarction
    • Muscles and Joints: Myalgia, arthralgia, and arthritis
    • GI System: Abdominal pain and GI bleeding
    • Peripheral Nervous System: Peripheral Neuritis