Electron microscopic studies. (A) Homozygous κ-CHEB mice. Electron microscopy, original magnification × 4000: numerous crystalline (arrows) and osmiophilic inclusions within the cytoplasm of proximal tubular cells. Note the alteration of apical brush border membrane (*) and duplication of the tubular basement membrane (white arrow). (B) κ-CHEB/κ-del mice. Electron microscopy, original magnification × 4000: proximal tubular cells contained few crystalline inclusions (arrows) and morphology of the brush border was preserved. (C) Homozygous κ-CHEB mice. Electron microscopy (original magnification × 12 000). Crystalline inclusions bound in a single membrane, probably related to lysosomes. Note the morphologic alterations of mitochondria. (D) Homozygous κ-CHEB mice. Electron microscopy (original magnification × 50 000) and (E) Patient CHEB. Kidney biopsy. Electron microscopy (original magnification × 80 000). Similar ultrastructural appearance of osmiophilic crystalline inclusions in patient CHEB and κ-CHEB mice, with an 80-Å periodic striation.