In a recent teaching case published in the American Journal of Kidney Diseases, Sharma et al describes a fascinating case of fibrillary glomerulonephritis that presented as rapidly progressive glomerulonephritis.  Fibrillary glomerulonephritis is a rare disease associated with hepatitis C, autoimmune diseases, and cancers. It falls under a category of pathologic diseases with organized deposits. The following questions will test your knowledge of diseases that lead to organized deposits in the kidney biopsy.

1. A 67-year-old man with lower extremity edema for many months now presents with nephrotic syndrome and 10 g of proteinuria. He has no other past medical history. Complements are normal and other serologies including antinuclear antibody and antineutrophil cytoplasmic antibody are negative. A fat pad biopsy done to rule out amyloidosis is inconclusive. A kidney biopsy revealed amorphous eosinophilic material infiltrating the mesangium and peripheral capillary walls on light microscopy, lambda light chain staining on immunofluorescence, and randomly arranged fibrillary deposits that are 10 nm in average diameter on electron microscopy (EM). Congo Red staining is positive. What is the most likely diagnosis?

Images courtesy of Dr. Helmut Rennke

A. Fibrillary Glomerulonephritis

B. AL Amyloidosis

C. Lupus Nephritis

2. A 56-year-old man with hypertension presents with a progressive rise in creatinine over the last few weeks. All serological testing is negative except for a mild elevation of the kappa:lambda ratio and a faint M spike of immunoglobulin G (IgG)/kappa. A kidney biopsy reveals thickened basement membranes on light microscopy and monoclonal IgG/kappa staining on immunofluorescence. Congo Red staining is negative. The EM shows organized deposits composed of microtubular structures with an average diameter of 45 nm arranged like stacks. A bone marrow biopsy confirms chronic lymphocytic leukemia. What is the most likely diagnosis for the kidney disease?

Image courtesy of Dr. Helmut Rennke

A. Fibrillary Glomerulonephritis

B. Monoclonal IgG/kappa deposition disease

C. Immunotactoid Glomerulonephritis

3. A 56-year-old man with hypertension presents with a gradual rise in creatinine over the last few weeks. All serological testing is negative except for a low C3. A kidney biopsy reveals thickened basement membranes on light microscopy, and immunofluorescence of IgG, IgM, and kappa, but very weak lambda staining. The EM shows organized curved microtubular deposits with a diameter of 55 nm arranged in stacks. A hepatitis panel is positive for hepatitis C polymerase chain reaction of >1 million copies. What is the most likely diagnosis on the kidney biopsy?

A. Immunotactoid Glomerulonephritis

B. AL Amyloidosis

C. Cryoglobulinemic Glomerulonephritis

4. A 30-year-old woman has a kidney biopsy done to evaluate 2g of proteinuria. The biopsy reveals a membranoproliferative pattern of injury on light microscopy. The immunofluorescence shows interrupted staining for IgM and C3 along the capillary wall, and coarse mesangial and peripheral capillary wall staining for collagen type III. The EM shows curved/frayed fibers with periodicity of 60 nm. What is your diagnosis?

Image from Alchi el al AJKD Review

A. Immunotactoid Glomerulonephritis

B. Fibronectin Glomerulonephritis

C. Collagenofibrotic Glomerulopathy

Post by Isaac E. Stillman, MD, Beth Israel Deaconess Medical Center, Boston, MA, and Dr. Kenar Jhaveri, eAJKD Blog Editor.

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