Transgenic mice kidneys by light microscopy. (A-B) Homozygous κ-CHEB mice. Semithin sections of araldite-included samples. Toluidine blue staining, original magnification × 100 (A) and × 400 (B). Numerous crystalline inclusions in the cytoplasm of proximal tubular cells (arrows and inset). Note the absence of myeloma casts in distal tubule lumens (A), and the normal appearance of glomerular tufts and Bowman capsules (A-B). Crystalline inclusions were not observed in the initial part of proximal tubules (B, asterisk). (C) κ-CHEB/κ-del mice. Semithin sections of araldite-included samples. Toluidine blue staining, original magnification × 400. Few crystalline inclusions were present within proximal tubules (arrow). (D) Patient CHEB. Araldite-inclusion, toluidine blue staining, original magnification × 1000. Massive cytoplasmic crystalline accumulation in proximal tubular cells, with some free crystals in tubular lumen (arrow). Inclusions were not observed in glomeruli.