A 48-year-old woman with breast carcinoma develops hematuria and proteinuria of 3 g/day. Light microscopy shows mesangial expansion and mild lobular accentuation. Electron microscopy reveals randomly oriented, nonbranching fibrils measuring 15 nm within the mesangium and glomerular basement membrane. Congo red stain is negative. Immunofluorescence shows smudgy polyclonal IgG and C3. The most likely diagnosis is:

• A Renal amyloidosis, AL type
• B Fibrillary glomerulonephritis ✓
• C Immunotactoid glomerulopathy
• D Diabetic nodular glomerulosclerosis

Explanation

Fibrillary glomerulonephritis shows Congo red negative, randomly arranged fibrils of 12 to 24 nm composed of polyclonal IgG with B3, now associated with DNAJB9 as a tissue biomarker, and it frequently accompanies autoimmune disease or malignancy. Amyloid fibrils are thinner (7 to 10 nm) and Congo red positive. Immunotactoid glomerulopathy shows larger microtubules over 30 nm arranged in parallel bundles with monoclonal immunoglobulin.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.