[Early lesions of the human kidney in paraproteinemie an electron microscopic study (author's transl)]

In paraproteinemia, especially in multiple myeloma, the origin and morphology of lesions in the kidneys still remain controversial. In many studies mostly of tissue obtained post mortem and examined with light microscopy, a discrepancy between impairment of renal function and minimal pathomorphological findings is often striking. The few studies done with the electron microscope up to now present a wide variety of morphological findings probably due to the different stages of kidney lesions examined, generally in patients with renal insufficiency and nephrotic syndrome. We have therefore tested the question whether early lesions are detectable in the nephron of patients with paraproteinemia who do not show any impairment of renal function.

Kidney biopsies were obtained from 8 patients with an average age of 58 years. 6 had multiple myeloma (3 IgG-, I IgA-, 2 Bence-Jones plasmacytoma), 1 Waldenström's disease and 1 an idiopathic paraproteinemia. Confirmation of the diagnoses was obtained by immunoelectrophoresis, bone marrow biopsy, and sternal puncture. In all cases creatinine clearance was normal and proteinuria was not increased substantially even in patients with a slight Bence-Jones-proteinuria. For electron microscopy small pieces from the renal biopsies were fixed in aldehydes followed by osmium tetroxide and embedded in Epon. The thin sections were stained with uranyl acetate followed by lead citrate...