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Difficulty: HardNephrology

Match each of the following patient clinical presentations with the most likely corresponding renal biopsy findings on light, immunofluorescence, or electron microscopy.

  • A 55-year-old man with a recent diagnosis of a solid organ malignancy presents with 5 g/day proteinuria, hypoalbuminemia, and severe lower extremity edema.Subepithelial electron-dense deposits with thickened glomerular capillary walls and a 'spike and dome' appearance.
  • A 48-year-old woman with chronic untreated hepatitis C infection presents with palpable purpura, hypocomplementemia, and a mixed nephritic-nephrotic urinary sediment.Subendothelial and mesangial immune complex deposits with duplication of the glomerular basement membrane ('tram-track' appearance).
  • A 62-year-old man presents with rapidly progressive renal failure, hemoptysis, negative anti-glomerular basement membrane antibodies, and normal serum complement levels.Fibrinoid necrosis and extensive crescent formation within Bowman space with absent or scant immunoglobulin staining.
  • A 25-year-old man with bilateral sensorineural hearing loss and anterior lenticonus presents with progressive renal insufficiency and microscopic hematuria.Variable thinning and thickening with longitudinal splitting and lamellation of the lamina densa on electron microscopy.

Answer

Solid tumor matches subepithelial deposits (Membranous nephropathy); Hepatitis C matches subendothelial deposits (Type I MPGN); Pulmonary-renal syndrome with normal complement matches fibrinoid necrosis and crescents without immunoglobulins (Pauci-immune GN); and Hearing loss with lenticonus matches lamellation of the lamina densa (Alport syndrome).
Each matching pair requires linking a classic systemic presentation to its definitive histologic findings. Membranous nephropathy (subepithelial deposits) is strongly tied to solid tumors. Type I MPGN (subendothelial deposits with double contours) is linked to Hepatitis C and cryoglobulinemia. Pauci-immune crescentic GN (crescents without immunoglobulin) is identified by pulmonary-renal symptoms without immune complex consumption (evidenced by normal complement). Alport syndrome (GBM splitting) presents with type IV collagen defects uniquely affecting the ears, eyes, and kidneys.

Step-by-Step Solution

1
Analyze the vignette of the 55-year-old man with solid organ malignancy and nephrotic syndrome.
Identified as secondary membranous nephropathy.
Solid tumors are classic secondary causes of membranous nephropathy, which presents with isolated massive proteinuria and pathologically shows subepithelial 'spike and dome' deposits.
2
Analyze the vignette of the 48-year-old woman with Hepatitis C, purpura, and a mixed urinary sediment.
Identified as cryoglobulinemia-associated Membranoproliferative Glomerulonephritis (MPGN).
HCV drives cryoglobulin production, which deposits in the subendothelial space, causing a 'tram-track' appearance on microscopy and hypocomplementemia.
3
Evaluate the 62-year-old man with pulmonary-renal syndrome, normal complement, and negative anti-GBM antibodies.
Identified as Pauci-immune crescentic glomerulonephritis (likely ANCA vasculitis).
Normal complement and negative anti-GBM effectively rule out Goodpasture syndrome and lupus/post-infectious glomerulonephritis, pointing strictly to pauci-immune crescentic GN.
4
Assess the 25-year-old man with hearing loss, lenticonus, and hematuria.
Identified as Alport syndrome.
Mutations in type IV collagen lead to sensorineural deafness, specific eye abnormalities, and characteristic splitting/lamellation of the glomerular basement membrane on electron microscopy.

Key Concept

Correlation of systemic clinical syndromes (malignancy, chronic infections, vasculitis, genetic disorders) with their specific glomerular histopathologic and electron microscopic biopsy patterns.
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Topics

Nephrology

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