Mesangiocapillary Glomerulonephritis

Background and Epidemiology, and Aetiology

• Also known as membranoproliferative glomerulonephritis
• Mainly occurs in children >5/young people
• Characterised by a diffuse thickening and lobular appearance of the glomerular basement associated with increased cellularity
• Can be primary (idiopathic) or secondary (more common)
  • Idiopathic can be classed as
    • Type I- subendothelial deposits of IgG/IgM and C3 (most common)
    • Type II- dense deposits of C3 in a linear fashion along the basement membrane
    • Type III- subendothelial and subepithelial deposits (usually as a result of scarring after HUS or TTP)
• Secondary disease is usually due to
  • Autoimmune diseases e.g. SLE, Rheumatoid arthritis, Coeliac disease
  • Infections, particularly Hep B and Hep C

Pathophysiology

• Primarily due to complement activation (resulting in decreased circulating complement)
  • Type I/Secondary MCGN is via the classical pathway and type II is via the alternative pathway
  • Type II- also many patients have autoantibodies against Nephritic factor which regulates complement and may lead to its excessive activation

Presentation

• May be asymptomatic with proteinuria/haematuria on urinalysis
• Proteinuria may be sufficient to cause a nephrotic syndrome
• In some cases, patients may present with an acute nephritic syndrome (more common in children)
  • Haematuria (microscopic or gross)
  • Proteinuria
  • Hypertension
  • +/- Uraemia and oliguria
• Other symptoms can include fat atrophy (strong association with partial lipodystrophy) which most commonly affects the upper limbs, trunk and face
  • Occasionally visual problems can occur and drusen/neovascularisation may be seen on fundoscopy
  • Both of these are associated with Type II disease (dense deposit disease- complement deficiency)

Investigations

• See also nephrotic syndrome
• Other tests which may be appropriate include autoantibodies (to rule out secondary causes), complement levels
• Kidney biopsy is usually the definite test

Management

• Treat any underlying causes
• If primary disease, immunosuppressive agents e.g. cyclophosphamide/MMF are usually the treatment +/- steroids
• Reduce any cardiovascular risk i.e. BP control with ACE inhibitors/ARBs

Prognosis varies between type (type II/dense deposit disease has a worse prognosis in general).  Around 50% will develop end-stage kidney disease in 10 years.

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