How are acute phase and late phase PAN?

Acute phase: • Transmural inflammation of the arterial wall and perivascular infiltration by neutrophils and eosinophils. • Fibrinoid necrosis • Thrombosis → infarction of the tissues supplied by the involved vessel. • Aneurysm (up to 1 cm in size) → may rupture → produce hemorrhage. Late phase: • Subacute and chronic stages: Acute inflammatory infiltrate replaced by mononuclear cells. • Fibrous thickening of the vessel wall → further occlusion of the vessel lumen.