Lipofuscin-like granules of the juxtaglomerular apparatus of the kidney. The diagnostic significance of a quasi-normal subcellular structure incidentally encountered in the course of routine ultrastructural evaluation of renal biopsies

Lipofuscin-like granules, first described by Biava and West in 1965, are a subcellular, quasi-physiologic finding mainly seen in the smooth muscle cells of renal arterioles, but also in juxtaglomerular cells and the lacis cells of human kidneys. They increase in number in subjects affected by arterial hypertension and diabetes. They do not correlate with a specific primary renal disease. Lipofuscin-like granules are not related to renin granules. The world literature on this subject is almost non-existent, and the awareness of this finding or its clinical significance among either pathologists or nephrologists is very poor. We incidentally observed these lipofuscin-like granules in 8 cases during the routine electron microscope examination of 440 renal biopsies, and report herein on their ultrastructural features. Six of these 8 patients were affected by arterial hypertension, one of whom was also concomitantly affected by diabetes mellitus. These lipofuscin-like granules appear as dense bodies with a lipid component, a coarsely granular matrix, and a crystalloid component which may appear in a band or dot pattern, according to the plane of sectioning. The pathologist has to be aware of these lipofuscin-like granules in order not to confuse them with the semicircularly organized (fingerprint) linear immune deposits associated with some specific glomerulopathies.