Electron-dense deposits in the renal arterioles of two patients with hypersensitivity vasculitis

Immune complex deposition in the vessel wall is presumed to be the major pathogenetic mechanism leading to hypersensitivity vasculitis. Despite this, histologic evidence of vascular immune complex deposition such as that provided by electron-dense deposits has been reported only rarely in dermal vessels and never in visceral organs. The cases of two patients with hypersensitivity vasculitis affecting primarily the skin and the kidney are reported. Clinical renal involvement was manifested by proteinuria, hematuria, and a moderate increase in serum creatinine in one case. Renal biopsy showed minimal glomerular changes in one patient and focal necrotizing glomerulitis in the other. The arterioles appeared normal on light microscopic examination. However, obvious electron-dense deposits in the arteriolar wall could be demonstrated electron microscopically in both cases. This observation lends strong support to the theory of immune-complex-mediated vascular damage as the main pathophysiologic mechanism in vasculitis with visceral involvement.