Glomerulonephritis, overview


##Basic introduction:

  • Glomerulonephritis (GN) refers to several renal diseases that are mainly characterized by inflammation of either glomeruli or the small blood vessels in the kidneys.
  • GN syndromes are classified into non-proliferative that normally results in nephrotic syndrome (in which the number of cells is not changed) and proliferative types that normally results in nephritic syndrome (in which case there are increase in number of cells in the glomerulus)
  • In nephrotic syndrome, there is inflammation of podocytes, which are cells lining the Bowman's capsule. This leads to the loss of proteins from the blood through urine. Also due to the reduced oncotic pressure in the blood because of proteinuria, sodium retention in the distal nephron and increased secretion aldosterone, edema occurs
  • In nephritic syndrome, inflammatory damage to cells lining the glomerulus destroys the epithelial barrier causing the loss of blood in through the urine. The renin-angiotensin system is also activated causing the reduced perfusion of juxtaglomerular apparatus leading subsequently to hypertension and oliguria.

## Non-proliferative or nephrotic syndrome class include the following:

  • Minimal change disease

_There are no microscopically visible changes in the glomerulus on microscopy

_It is the most common cause of the nephrotic syndrome in children

_It is managed with corticosteroids

_It does not progress to chronic renal disease

  • Focal segmental glomerulosclerosis

_This is associated with sclerosis (hardening) of parts of some glomerulus

_Its causes include HIV, heroin abuse and idiopathic

_Corticosteroids can provide some relief

_50% of cases will end up with renal failure

  • Membranous glomerulonephritis, MGN

_It can manifest either nephrotic or a nephritic features

_It is caused by auto-antibodies to phospholipase A2 receptor (2/3 of cases), cancers of the lungs, cancers of GIT, hepatitis B virus infection, malaria, penicillamine, systemic lupus erythematosus and cerebral shunts among others.

_The pathology of MGN involves thickening of glomerular basement membrane with minimal hyperproliferation of the glomerular cells. Features of Type III hypersensitivity reaction are also evident.

_1/3 of patients remain with the disease, 1/3 remit, and 1/3 progress to end-stage kidney failure.

  • Thin basement membrane disease

_This is an autosomal dominant inherited disease characterized by thin glomerular basement membranes

_It is a benign disease with key presentations of persistent microscopic hematuria as well as mild proteinuria.

_It shows very good prognosis.

## Proliferative or nephritic syndrome class include the following:

  • IgA nephropathy (Berger's disease)

_It is the dominant type of glomerulonephritis

_Its pathology involves deposition of IgA in the space between glomerular capillaries

_Its clinical presentation include isolated visible or occult hematuria with or without a low-grade proteinuria

  • Post-infectious glomerulonephritis (PIGN)

_It occurs as a late complication of pharyngitis or skin infections mainly due to a nephritogenic strain of β-hemolytic streptococci (although other bacterial infections can as well)

_It is the main cause of Acute Glomerulonephritis (AGN). For the details refers to disease description “Glomerulonephritis, Acute Post-streptococcal, APSGN” in this publication.

_Its main clinical features include microscopic hematuria, brown/pink and foaming urine, proteinuria, edema (with puffiness of the face), and hypertension

  • Rapidly progressive glomerulonephritis, RPGN (crescentic glomerulonephritis)

_RPGN is characterized by a rapid, progressive deterioration in renal function presenting as a nephritic syndrome

_It shows very prognosis

_There are 3 main types of RPGN: Type 1, Type 2 and Type 3

_Type 1 (or Goodpasture syndrome): it is an autoimmune disease of the lung where IgG antibodies directed against the glomerular basement membrane are produced.  These IgG antibodies trigger an inflammatory reaction that culminates to the nephritic syndrome as well as the coughing up of blood. It managed with high dose methylprednisolone (or any other steroid), cyclophosphamide and plasmapheresis.

_Type 2 RPGN is caused by the immune-complex-mediated reaction associated with systemic lupus erythematosus, post-infective glomerulonephritis, IgA nephropathy, and IgA vasculitis

_Type 3 RPGN (Pauciimmune type): It is associated with vascular inflammation

  • Membranoproliferative glomerulonephritis, MPGN (mesangiocapillary glomerulonephritis)

_The pathology of this disease involves increased number of cells in the glomerulus and changes in the glomerular basement membrane

_Two primary subtypes exist namely Type 1 MPGN and Type 1 MPGN

_Type 1 MPGN (caused by circulating immune complexes) is caused by diseases such as systemic lupus erythematosus, hepatitis (B & C) infection among other infections. Circulating immune complexes may activate the complement system, leading to inflammation and an influx of inflammatory cells

_Type 2 MPGN (Dense Deposit Disease) is caused by an excessive activation of the complement system.

_It presents with features of nephritic syndrome as well as hypocomplementemia.

_The condition has a poor prognosis

  • As GN is somehow a conglomerate of diseases its symptoms and signs depend on the specific disease entity
  • Hematuria and/or proteinuria
  • Acute renal injury
  • Chronic renal disease

## Nephrotic syndrome:

  • The distinguishing factor is proteinuria
  • Edema
  • Reduced protein in the blood (especially albumin)
  • Hypercholesterolemia/hyperlipidemia (due to increased production of lipids by the liver)

##Nephritic syndrome

  • The distinguishing factor is the presence of blood, mainly RBC casts and some dysmorphic RBC.
  • Oliguria
  • Hypertension
  • Urinalysis
  • Blood urea (normal but it may be elevated in oliguric phase)
  • Throat and/skin swab (for streptococcus)
  • Renal ultrasound
  • Antistreptolysin O titer
  • Renal biopsy (not always)
  • Renal cancer
  • Bladder cancer
  • Pre- or post-renal failure
  • Nephrolithiasis
  • Prevention depends on the type of GN, but generally, the available effective measures are minimal
  • Management depends on the type of GN
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