Kidney nontumor / medical renal

• Idiopathic glomerular disease that causes nephrotic syndrome
• Little or no light or immunofluorescent microscopic abnormalities
• Diffuse podocyte foot process effacement on electron microscopy (BMC Nephrol 2018;19:207)

• Extensive foot process effacement appears to be due to epithelial injury with loss of glomerular anionic charge (Kidney Int 1984;25:696)
• Abnormal T cell and B cell function and immune dysregulation (Pediatr Nephrol 2018;33:573, Clin J Am Soc Nephrol 2016;11:710)
• Unknown circulating factor that triggers podocyte dysfunction has been postulated (Pediatr Nephrol 2018;33:1101)
• Nephrin autoantibodies have been discovered in a subset of adults and children with minimal change disease; this aligns with published animal studies and provides further support for an autoimmune etiology (J Am Soc Nephrol 2022;33:238)
• Minimal change disease, diffuse mesangial hypercellularity and focal segmental glomerulosclerosis may be a continuum of the same disease (Kidney Int 2004;65:1690)

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• Nephrotic syndrome
• Proteinuria selective for albumin, causing hypoalbuminemia leading to severe edema
• Lipiduria, hypercholesterolemia but usually no hypertension, no hematuria and no azotemia
• Microhematuria (10 - 30%)
• Can present as acute renal insufficiency in adults (Clin J Am Soc Nephrol 2017;12:332)
• Can present with IgA nephropathy (Clin J Am Soc Nephrol 2014;9:1033)

• 2 and 15 year old boys with steroid responsive nephrotic syndrome complicated by cerebral venous sinus thrombosis (Nefrologia 2015;35:497)
• 29 year old woman with type I neurofibromatosis and complete remission after neurofibroma resection (Korean J Intern Med 2017;32:186)
• 33 year old man with severe chronic sinusitis (Intern Med 2015;54:2373)
• 43 year old man with nephrotic syndrome following the COVID-19 vaccine (BMC Nephrol 2021;22:376)
• 50 year old woman with minimal change disease after a type B influenza infection (BMC Nephrol 2018;19:162)
• 63 year old man with nephrotic syndrome (JNMA J Nepal Med Assoc 2022;60:399)
• 68 year old man with marginal zone MALT lymphoma manifesting as nephrotic range proteinuria (Clin Nephrol 2016;85:184)

• Corticosteroids
• Immunosuppressive agents in steroid resistant cases (cyclophosphamide, rituximab, abatacept) (Kidney Int 2013;83:511, Pediatr Nephrol 2015;30:469)

• Glomerulus normal by light microscopy except for variable podocyte hypertrophy
• Protein reabsorption droplets in tubules (Zhou: Silva's Diagnostic Renal Pathology, 2nd Edition, 2017)

Contributed by Ana Belén Larqué, M.D., Ph.D.

• Negative except for variable focal IgM with or without C3
• Punctate IgG podocyte staining in a subset of cases associated with antinephrin antibodies (J Am Soc Nephrol 2022;33:238)

• Extensive foot process effacement (foot processes retract into cell bodies, not actually fusion) (Nephrology (Carlton) 2014;19:392)
• Microvillous transformation of epithelial cells, cyst formation

Contributed by Ana Belén Larqué, M.D., Ph.D. and Nicole K. Andeen, M.D.


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Which of the following is true about minimal change glomerulopathy?

1. Interstitial inflammation and fibrosis are usually absent
2. It is the most common type of nephrotic syndrome in adults
3. Monoclonal antibody therapy should be the first line therapy
4. Pretreatment biopsy is always done

A. Interstitial inflammation and fibrosis are usually absent. Answer B is incorrect because membranous nephropathy is the most frequent cause of nephrotic syndrome in adults. Answer C is incorrect because corticosteroids are the first line therapy. Answer D is incorrect because in the pediatric setting, a renal biopsy is usually not performed if presentation is typical and the patient responds to therapy with oral prednisone at conventional doses.

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Reference: Minimal change glomerulopathy

Which of the following signs and symptoms is common in minimal change disease?

1. Azotemia
2. Hypertension
3. Macrohematuria
4. Selective proteinuria

D. Selective proteinuria. Minimal change disease usually presents with proteinuria selective for albumin, causing hypoalbuminemia leading to severe edema. Answers A - C are incorrect because minimal change disease is associated with lipiduria and hypercholesterolemia but usually no hypertension, no hematuria and no azotemia.

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Reference: Minimal change glomerulopathy

Which of the following renal lesions is most likely to be present in minimal change disease?

1. Acute tubular necrosis
2. Glomerular crescent formation
3. Mesangial immune complex deposition
4. Podocyte foot process effacement

D. Podocyte foot process effacement. Minimal change disease is an idiopathic glomerular disease that causes nephrotic syndrome with little or no immunofluorescent microscopic abnormalities. The pathologic hallmark of disease is absence of visible alterations by light microscopy and effacement of foot processes by electron microscopy.

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Reference: Minimal change glomerulopathy