Electron microscopy of nephropathia epidemica. Renal tubular basement membrane.

Tubular basement membranes in kidney biopsies from 18 patients with nephropathia epidemica were studied by electron microscopy. Both in the cortex and in the medulla there was splitting of the basement membrane. Thickened basement membrane around occasional tubules contained membrane vesicles, usually empty but also with a core and a diameter of approximately 180 nm. Membranous convoluted structures and light finely fibrillar areas in the basement membranes were seen. Splitting of the basement membrane was most prominent in the medulla, and the membrane was filled with round to oval particles 55 to 470 nm in diameter. Of the possible mechanisms of damage at the basement membrane level in this disease, the findings suggest liberation of antigen from the tubular cells and reaction of circulating antibodies with the antigen in the basement membrane.