Membranous Nephropathy

1. Know that Membranous Nephropathy is the most common cause of NS in adults

2. Name the causes of secondary Membranous Nephropathy
   

   • Drugs – penacillamine, gold, captopril

   • Infection – hepatitis B, syphilis, various parasitic diseases

   • SLE – careful to check for in young women with Membranous Nephropathy
     

   • Malignancy

• Especially in lung, breast, and GI

• Important to check for in older patients with Membranous Nephropathy
  

• Sjogren’s syndrome
• Mixed connective tissue disease
• Systemic metabolic disorders – e.g, diabetes, thyroiditis
• Sickle cell disease
  

3. Know the Light Microscopy, Immuno Fluorescense, and Electron Microscopy findings of Membranous Nephropathy
   

• LM

• Glomeruli appear normal early in disease
• Later, diffuse thickening of capillary walls occurs
• Silver stain demonstrates spikes in BM between deposits
• Trichrome stain may reveal deposits themselves

• IF – diffuse, granular pattern of IgG and C3 deposits along subepithelial surface of capillary loops
• EM - Electron dense deposits in subepithelial distribution with effacement of overlying foot processes

4. Know the age, clinical manifestations and HLA antigens of patients with Membranous Nephropathy
   

• Mean age of onset is 40-50
• Most present with nephrotic syndrome (~20% with asymptomatic proteinuria)
• Microscopic hematuria present in ~60%
• RBC casts rare
• HTN is uncommon
• Renal function is usually normal
• IC in blood is RARE – complexes are formed in situ
• Similar to Heymann nephritis in rats  linked to HLA locus  caused by susceptibility to Ab to a renal auotoantigen
  

5. Know how to work up a case of Membranous Nephropathy
   

• Determination of antinuclear and antiDNA Ab, serum complement, rheumatoid factor, cryoglobulin, Hepatitis B Ag, VDRL, and tests to exclude diabetes

• Older patients should have a clinical and radiologic search for occult malignancy

• Hematuria and flank pain may indicate pulmonary emboli

• May have other glomerular disease “ on top of ” Membranous Nephropathy
  

6. Know the prognosis of Membranous Nephropathy
   

• Widely variable clinical course

• 25% -Spontaneous remission

• 25% have persistent nephrotic range proteinuria for many years while maintaining normal renal function

• Remaining 50% show progressive deterioration of renal function that results in end-stage renal disease in about 15 years

• No criteria have been identified to predict which course an individual will follow

Category: Pathology Notes