Kidney nontumor / medical renal

• Diabetic kidney disease is a morphologic structural change in the kidney induced by longstanding hyperglycemia manifested as relentless matrix expansion

Contributed by Khaled A. Murshed, M.D., Noheir M. Taha, M.B.B.Ch., M.D. and Mohammed Akhtar, M.D.

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Contributed by Khaled A. Murshed, M.D., Noheir M. Taha, M.B.B.Ch., M.D. and Mohammed Akhtar, M.D.

Contributed by Khaled A. Murshed, M.D., Noheir M. Taha, M.B.B.Ch., M.D. and Mohammed Akhtar, M.D.

• Renal amyloidosis:
  • Mesangial nodules are Congo red positive with apple green birefringence under polarized light (Adv Anat Pathol 2020;27:87)
• IgA nephropathy:
  • IgA dominant immunofluorescent pattern
• Renal monoclonal immunoglobulin light chain deposition disease or monoclonal immunoglobulin heavy chain deposition disease:
  • Immunofluorescence reveals diffuse linear staining of the glomerular basement membrane with monoclonal immunoglobulin light or heavy chains
  • Electron microscopy shows a continuous band of electron dense granular powdery deposits within the mesangial nodules, subendothelial space and along external side of the tubular basement membranes
• Membranoproliferative glomerulonephritis (MPGN):
  • Marked endocapillary proliferation with double contouring of the peripheral capillary loops identified on PAS and Jones methenamine silver stains
  • Immunofluorescence shows diffuse granular glomerular capillary loop and mesangial deposition of C3 with variable immunoglobulin deposition
  • Electron microscopy shows mesangial and subendothelial electron dense deposits
• Dense deposit disease:
  • Light microscopic features may resemble MPGN, immunofluorescence reveals deposition of C3 only
  • Ultrastructurally characterized by large intramembranous nonimmune complex type electron dense deposits
• Fibrillar glomerulonephritis:
  • Deposition of usually polyclonal IgG by immunofluorescence, corresponding haphazardly arranged fibrils measuring 12 - 24 nm diameter by electron microscopy and DNAJB9 positivity by immunohistochemistry
• Immunotactoid glomerulonephritis:
  • Deposition of usually monotypic IgG by immunofluorescence and corresponding haphazard to parallel arranged fibrils with hollow core measuring ≥ 30 nm diameter by electron microscopy
• Fibronectin glomerulopathy:
  • Glomerular nodules are PAS positive but silver and Congo red stains are negative
  • Electron microscopy shows electron dense deposits in the mesangium that are finely granular or have a fibrillary substructure with randomly arranged 12 - 16 nm fibrils
  • Diagnosis confirmed by intense immunohistochemical staining for fibronectin in the mesangium and along the glomerular capillaries

A 57 year old woman was found to have proteinuria. A renal biopsy showed the findings in the image above (PAS). Which of the following conditions is the most important differential diagnosis?

1. Lupus nephritis
2. Membranous glomerulonephritis
3. Minimal change disease
4. Postinfectious glomerulonephritis
5. Renal amyloidosis

E. Renal amyloidosis. The image shows diabetic kidney disease. In renal amyloidosis, mesangial nodules similar to those seen in diabetic kidney disease can occur. Answer A is incorrect because although lupus nephritis can have a wide morphological spectrum, mesangial nodules are very uncommon. Answer B is incorrect because in membranous glomerulonephritis, there will be mainly thickening of glomerular basement membranes. Answer C is incorrect because in minimal change disease, mesangial nodules do not occur. Answer D is incorrect because the main histologic change in postinfectious glomerulonephritis is endocapillary hypercellularity.

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Reference: Diabetic kidney disease

On immunofluorescent microscopy, what is the usual finding in diabetic kidney disease?

1. Diffuse coarse granular staining of C3 along the glomerular capillaries and mesangium
2. Diffuse coarse granular staining of IgG along the glomerular capillaries
3. Diffuse mesangial staining for IgA
4. Dull linear staining of glomerular and tubular basement membranes for IgG
5. Immunofluorescent microscopy is typically negative

D. Dull linear staining of glomerular and tubular basement membranes for IgG. In diabetic kidney disease, there will usually be linear staining along glomerular and tubular basement membranes of IgG. Answer C is incorrect because mesangial staining for IgA is seen in IgA nephropathy. Answer A is incorrect because coarse granular mesangial and capillary staining of C3 is seen in C3 glomerulonephritis. Answer B is incorrect because granular staining of IgG along the capillary walls is seen in membranous glomerulonephritis. Answer E is incorrect because immunofluorescence studies are negative in minimal change disease.

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Reference: Diabetic kidney disease

In a patient suspected to have diabetic kidney disease, what is the earliest structural change in a kidney biopsy recognized by electron microscopy?

1. Deposits of randomly oriented nonbranching fibrils in the mesangium
2. Diffuse effacement of podocyte foot processes
3. Diffuse thickening of the glomerular basement membrane
4. Electron dense subepithelial deposits
5. Expansion of the mesangial regions

C. Diffuse thickening of the glomerular basement membrane. In patients with diabetic kidney disease, the earliest ultrastructural change seen is thickening of glomerular basement membrane, which precedes other morphological changes. Answer A is incorrect because deposits of nonbranching fibrils are seen in amyloidosis. Answer B is incorrect because effacement of podocyte foot processes is seen in minimal change disease and focal and segmental glomerulosclerosis. Answer D is incorrect because electron dense subepithelial deposits are seen in membranous glomerulonephritis. Answer E is incorrect because although expansion of mesangial region occurs in diabetic kidney disease, it develops later.

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Reference: Diabetic kidney disease