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Kidney Week

Abstract: PO1945

Simultaneous Light-Chain Proximal Tubulopathy (with Crystals), Myeloma Casts Nephropathy, and Intratubular Amyloidosis in a Patient with Monoclonal Gammopathy of Renal Significance

Session Information

Category: Pathology and Lab Medicine

  • 1600 Pathology and Lab Medicine

Authors

  • Al Shaarani, Majd, Icahn School of Medicine at Mount Sinai, New York, New York, United States
  • Salem, Fadi E., Icahn School of Medicine at Mount Sinai, New York, New York, United States
Introduction

Monoclonal gammopathy of renal significance (MGRS) is an important complication of monoclonal disease in the kidney with a spectrum of histological changes involving glomerular and tubulointersitial compartments. While MGRS is usually present as a single pathological entity, a combined two or more pathology features in a single patient is rarely reported.

Case Description

A 67 year old male admitted to the hospital for nausea and vomiting in association with AKI (creatinine 9.06 mg/dL), severe anemia (hemoglobin 6.4 g/dL) and hypercalcemia. Urinalysis showed 4-10 RBCs and proteinuria of 30 mg/dL. SPEP detected a monoclonal IgG kappa light chain. The patient received 2 units of blood transfusion pending further study and hematology consult.
Kidney biopsy showed a few thick angulated atypical casts in the distal tubules that show positive birefringent apple green staining by Congo red (Fig 1 A&B). By immunofluorescence, the casts are positive for kappa light chain with negative lambda (Fig 1 C&D). In addition, few proximal tubules show rounds or needle-shape intracytoplasmic structures (Fig 2 A&B). Ultrastructural examination demonstrates intracytoplasmic needles, rod, rhomboid or hexagonal crystals (Fig 2 C&D).

Discussion

The pathophysiological features of MGRS are distinctive, yet it can occur simultaneously in one patient. A throughout pathology and clinical assessment is essential in order to guide the treatment.

A.Atypical cast with sharp edges surrounded by epithelial cells of distal tubules (PAS). Congo red-positive intratubular casts (inset)
B.Intratubular casts are positive for Kappa light chain (Direct Immunofluorescent)
C.Renal cortex shows intracytoplasmic magenta-colored structures (arrow) in proximal tubules (PAS)
D.Ultrastructural images of proximal tubular cells show rod and rhomboid intracytoplasmic crystals (black arrow) and hexagonal and oval-shape crystal (white arrow/inset) (transmission EM)