Round “virus-like” extracellular particles in glomerular tufts

The round “virus-like” extracellular particles (REP), observed in 86 of 190 renal biopsies are round or oval entities with an outer diameter ranging from 400 to 1200 A. Sometimes they are electron-dense, homogeneous particles; sometimes they assume the shape of small vesicles with or without an electron-dense core. The REP are localized between the podocytes or the mesangial cells on one side and membranous material (glomerular basement membrane or mesangial matrix) on the other side. Their number ranges from a few units to several hundreds. They occur in widely differing instances. No evidence supports the hypothesis of their viral identity; a localized degenerative process is more likely.