Immune-mediated disease of the kidneys affecting the glomeruli

Aetiology

• Majority are idiopathic (see notes)
• Secondary causes include:
  • Goodpastures
  • Circulating immune complexes
    • Infection - hepatitis, bacteria (post strep), HIV
    • Drugs - gold, penicillamine
    • Cancer - any but often lymphomas
  • Vasculitis
    • GPA - cANCA
    • MPA - pANCA

Pathophysiology

• Disruption to the glomerular capillary wall leads to haematuria and/or proteinuria
• Site and type of injury determines clinical presentation

Damage to endothelial or mesangial cells

• Damage to endothelial or mesangial cells leads to a proliferative lesion and red cells in urine
• Inflammation within the mesangium results in proliferation, release of Ang2 and chemokines and attraction of inflammatory cells
• Damage to endothelial cells results in vasculitis

Damage to podocytes

• Damage to podocytes leads to a non-proliferative lesion and protein in urine
• When cells are damaged they will atrophy, resulting in loss of size/charge specific barrier

Histological classification

• Proliferative or non-proliferative - usually refers to presence or absence of proliferation of mesangial cells
• Focal/diffuse - less or more than 50% of glomeruli are affected
• Global/segmental - all or part of glomerulus affected
• Cresentic - presence of crescents (epithelial cell extracapilalry proliferation e.g. RPGN in vasculitis)

Clinical features