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March 1, 2018

Light Chain Proximal Tubulopathy Amyloid Proximal Tubulopathy Type

The two most common morphologic variants of light chain proximal tubulopathy (LCPT) are LCPT with and without crystal formation. Two additional rare variants can also be seen, namely amyloid proximal tubulopathy and LCPT with fibrillary aggregates. The histopathologic features of amyloid proximal tubulopathy are shown here. (A and B) Proximal tubules have scattered cytoplasmic inclusions (arrows) that stain blue on (A) Masson trichrome stain and are (B) Congo red positive (original magnification × 400). (C) The cytoplasmic inclusions show lambda restriction (arrow) by immunofluorescence (fluorescein-conjugated anti-human lambda; original magnification × 400). (D) Transmission electron photomicrograph showing an aggregate in the proximal tubule cytoplasm which has the typical "fluffy" appearance of amyloid (unstained; original magnification × 8000).