Medium vessel Vasculitides

Question 1

POLYARTERITIS NODOSA

Answer 1

General features

• In middle aged adults who may had previous HBV or other viral infection; seems mediated by immune complex deposition (eg., HBsAg-HBsAB) in arteries
• Necrotizing arteritis involving most often renal arteries > heart >liver > GI > muscles > other
• Negatives: does not involve pulmonary arteries and glomerular capillaries; negative for ANCA autoantibodies

Morphology

• Simultaneous presence of early and healed lesions
• Early lesions: segmental fibrinoid necrosis of arterial wall with transmural and periadventitial inflammatory infiltrates; consequences:
  1) vessel wall weakening: microaneurysm formation, rupture, hemorrhage in the adjacent tissues;
  2) endothelial necrosis: thrombosis and distal infarcts
• Healed lesions: fibrous thickening of the arterial wall, scars at sites of infarction

Clinical features

• Fever, malaise, weight loss, eosinophilia in peripheral blood + presentation related to the tissues involved
• Multiple small infarcts in the kidneys: increased se-creatinine, hypertension, hematuria, proteinuria
• Multiple small infarcts in the heart  progressive heart failure (ECG changes, serum elevation of creatine kinase MB, coronarography: significant stenosis is not present at the orifices) • Etc.,

Question 2

KAWASAKI DISEASE

Answer 2

General features

• Pathomechanism: mediated by anti-endothelial cell antibodies?
• Usually self-limited illness in infants and children

Morphology

• Affects medium and small arteries; coronary arteries are often involved
• Necrotizing arteritis with thrombosis and aneurysm formation + rupture

Clinical features

• Acute febrile illness, oral/conjunctival erythema, skin rash, and lymphadenomegaly
• Myocardial infarction