Fig. 1

Pathologic findings of kidney biopsy tissue in Case 1. An ordinary protein cast with a “fractured” appearence and peripheral cellular reaction, which was weakly stained in PAS staining (a) (original magnification× 1000). A cast with an unique shape, that had a lightly stained central area and a deeply stained burr-like edge in PASM-Masson trichrome double staining (b), PAS staining (c) and Masson trichrome staining (d) (original magnification × 1000). The above unique casts stained with Congo red under ordinary light microscope (e), polarized light microscope (f) and fluorescence microscope (g) (original magnification × 400). The unique casts with strong staining of κ light chain (h) and no staining of λ light chain (i) (fluorescence micrographs × 400). Numerous randomly arranged unbranched fibrils with a diameter of 8–12 nm in a unique cast (j) (electron micrograph × 50,000)