Amyloid proximal tubulopathy: a novel form of light chain proximal tubulopathy

Light chain proximal tubulopathy is a paraproteinemic-related kidney disease most commonly seen in patients with a plasma cell dyscrasia. The classic description is that of proximal tubules with kappa-restricted intracytoplasmic crystals in a patient with a clinical Fanconi's syndrome. Recently, other variants of light chain proximal tubulopathy have been described including those without crystal formation. We expand the morphologic spectrum in this report of a patient who presented with acute renal failure, proteinuria and hematuria. Biopsy revealed proximal tubulopathy in which the proximal tubules show intracytoplasmic amyloid formation. This is the first description, to our knowledge, of amyloid proximal tubulopathy.