Cyclosporine A-Mediated renal lesion in a child with intractable proteinuria

Abstract

The histopathological observation of an 8-year-old boy who received cyclosporine A (CyA) for the treatment of persistent proteinuria is presented. In the renal biopsy specimen, typical CyA cytotoxic changes, such as juxtaglomerular apparatus hyperplasia and arteriolar hyalinosis, were observed. Electron microscopically, tubular epithelial cells and arteriolar smooth muscle cells were observed to have enlarged lysosomes, fine vacuoles, and/or enlargement and intracristal swelling of mitochondria. In the area of focal interstitial fibrosis, fibroblast-like cells (myofibroblasts) contained similar cytoplasmic vacuoles with a membranous substance. Although most vacuoles may have been formed due to dilatation of the endoplasmic reticulum, some vacuoles seemed to have originated from mitochondria or autolysosomes in tubular epithelial cells, smooth muscle cells, and fibroblast-like cells. These degenerative changes of organella may take part in the process that resulted in hyalinosis and interstitial fibrosis.