Glomerulonephritis, Acute

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DESCRIPTION

  • Acute glomerulonephritis (GN) is an inflammatory or immune-mediated process involving the glomerulus of the kidney, resulting in a clinical syndrome consisting of sudden-onset of hematuria, proteinuria, and renal insufficiency (1).
  • Acute GN may be caused by primary glomerular disease or secondary to systemic disease.
  • Clinical severity ranges from self-limited asymptomatic microscopic or gross hematuria to a rapidly progressive loss of kidney function over days to weeks.
ALERT

Urgent investigation and treatment are required to avoid irreversible loss of kidney function and subsequent progression to chronic kidney disease and end-stage renal disease.

EPIDEMIOLOGY

  • Infection-related GN
    • Acute poststreptococcal GN (APSGN) most commonly manifests children and occurs about 2 weeks after resolution of group A β-hemolytic Streptococcus infection. This occurs in high frequency in highly populated and economically disadvantaged communities around the world. As APSGN has sharply declined in the Western world, the number of Staphylococcus infection-associated GN (SAGN) cases has increased in patients aged 50 to 80 years (2).
    • Can also occur as a result of other bacterial infections, such as infective endocarditis, VP shunt nephritis, or less commonly with viral, helminthic or parasitic infections
  • IgA nephropathy
    • Most common primary GN in the world
    • Median age at diagnosis is 40 to 45 years in Western nations.
    • Incidence differs geographically: Asia > United States
    • HSP, the form with extrarenal manifestations, typically occurs in children <10 years old.
  • Anti-GBM disease
    • Goodpasture syndrome: a notable cause of pulmonary–renal syndrome
    • Peak distribution in 3rd and 6th to 7th decades
  • ANCA-associated GN
    • Often has a relapsing and remitting course
    • Four disease presentations:
      • Granulomatosis with polyangiitis (GPA), formerly Wegener granulomatosis
      • Microscopic polyangiitis (MPA)
      • Isolated pauci-immune GN—when isolated to kidneys
      • Eosinophilic GPA, formerly Churg-Strauss disease—GN relatively common but renal involvement rarely severe
  • MPGN
    • May be primary or secondary to systemic diseases
    • Epidemiology varies depending on the mechanism of injury and is more often a subacute or chronic presentation.
  • Lupus nephritis (LN)
    • About 20%–60% of systemic lupus patients will have renal involvement.
    • Incidence of LN is higher among black and Hispanic populations in comparison to white populations.
    • 6 classes
      • Minimal mesangial LN
      • Mesangial proliferative LN
      • Focal LN (can be proliferative [active] and/or sclerosing [chronic] disease)
      • Diffuse LN (can be proliferative [active] and/or sclerosing [chronic] disease)
      • Membranous LN
      • Advanced sclerotic LN
  • Cryoglobulin-associated vasculitis
    • 80% of cases with hepatitis C virus (HCV) infection
    • May also be associated with autoimmune disease or dysproteinemia

Prevalence

  • In patients >65 years of age, with an average age of 75 years, about 1.2% of people are affected by either primary or secondary GN.
  • In patients between the ages of 37 and 65 years, GN was much less commonly seen, with only about 0.12% of people affected by either primary or secondary GN (3).
  • The incidence and prevalence of GN in children is unknown. ASPGN is the most common type, but has diminished over the years.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Systemic and/or local immune activation causes glomerular injury.
  • Immune complex mediated: antigen–antibody formation and deposition in the kidneys; immune complexes are seen on immunofluorescence.
    • APSGN
    • SAGN
    • IgA nephropathy
    • MPGN
      • Cryoglobulin-associated GN
    • LN
  • Direct antibody-mediated injury, linear staining on immunofluorescence
    • Anti-GBM disease
  • Pauci-immune GN, not seen on immunofluorescence staining
    • ANCA-associated GN
  • Alternative complement pathway dysregulation
    • C3 glomerulopathy

RISK FACTORS

  • Epidemics of nephritogenic strains of streptococci are triggers for APSGN.
  • Anti-GBM disease has been associated with prior pulmonary injury and inhalation exposures, such as hydrocarbon solvents.
  • ANCA-associated GN may be drug induced (e.g., hydralazine, levamisole-contaminated cocaine) and is also associated with environmental exposures such as silica.
  • Hepatitis B is associated with MPGN. Hepatitis C is associated with both MPGN and cryoglobulinemic GN.

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