A new type of idiopathic glomerular disease is reported in a 49-year-old Italian woman who presented with uncharacteristic renal symptoms, i.e., hypertension and slight proteinuria. Clinical investigation excluded a familial renal disease and more specifically nail-patella syndrome. Diagnostic renal biopsy by light microscopy showed a picture similar to membranoproliferative glomerulonephritis. The enlarged glomeruli were lobulated, the peripheral basement membranes were thickened by the deposition of light-microscopically undefined material, cell proliferation was lacking. By electron microscopy, the material was nonhomogenous, partly granular partly fibrillar, containing typical collagen fibers. The latter were identified as collagen type III, to a lesser extent collagen type I. Review of the literature resulted in 12 similar or identical cases reported from Japan and one additional case reported in a white American female. Evidence of systemic disease is lacking. Etiology and pathogenesis are elusive. A progressive deterioration of renal function must be expected. Collagen type III glomerulopathy is suggested as term of this new type of idiopathic glomerular disease.

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