3. Glomerular diseases Flashcards
Clinical manifestations of glomerular diseases
1) nephrotic syndrome
2) nephritic syndrome
3) rapidly progressive glomerulonephritis
4) microscopic hematuria
5) chronic renal failure
Characteristics of nephrotic syndrome
- Heavy proteinuria
- >3.5g of protein loss/24 hours
- Urine appears frothy
- May be selective or non-selective in nature - Hypoalbuminemia
- Plasma albumin <3g/dL
- Albumin loss in urine overwhelms liver capacity to maintain normal serum albumin - Anasarca
- Generalized edema due to decrease in plasma oncotic pressure
- Marked periorbital edema, pedal edema, facial & abdominal swelling - Hyperlipidemia
- Due to compensatory increase in synthesis of lipoproteins by liver - Lipiduria
- Due to hyperlipidemia as well as a leaky glomerular filter allowing leakage of lipoproteins into urine - Others
- Loss of immunoglobulins: increased susceptibility to Staphylococcal & Pneumococcal infections
- Loss of anticoagulants & antiplasmins: thrombotic & thromboembolic complications
Causes of nephrotic syndrome
- Primary glomerular diseases
- Minimal change disease
- Membranous glomerulopathy
- Focal segmental glomerulosclerosis
- Membranoproliferative glomerulonephritis - Systemic disease
- Diabetes mellitus
- Amyloidosis
- Systemic lupus erythematosus
- Drugs (NSAID, penicillamine, street heroin)
- Infection (HBV, HCV, malaria, syphilis, HIV)
- Malignancies (multiple myeloma, lymphoma)
- Heterozygous Alport disease
Clinical features of nephrotic syndrome
Age is important in differential diagnosis of cause of
nephrotic syndrome
- Childhood nephrotic syndrome is almost always sensitive to steroid treatment (minimal change disease)
- Only when the child does not respond to steroid treatment is a renal biopsy performed
Characteristics of nephritic syndrome
- Oliguria
- Decrease in urine volume due to poor filtration - Azotemia
- Elevation of serum creatinine & blood urea nitrogen levels - Gross hematuria
- Presence of red blood cells in the urine
- Often with red cell casts under microscopy - Edema
- Due to fluid retention increasing plasma hydrostatic pressure
- Usually not as prominent as in nephrotics - Hypertension
- Due to fluid retention - Proteinuria
- Mild to moderate, sometimes in nephrotic range
Causes of nephritic syndrome
- Primary glomerular diseases
- Post-streptococcal glomerulonephritis
- IgA nephropathy - Systemic disease
- Goodpasture syndrome
- Systemic lupus erythematosus
- Systemic vasculitis (e.g. polyarteritis nodosa)
- Infective endocarditis
- Henoch-Schonlein purpura
Clinical features of nephritic syndrome
- 3 possible outcomes:
- Complete resolution with no residual damage
- Rapid progression to rapidly progressive glomerulonephritis causing acute renal failure
- Slow progression to chronic renal failure (chronic glomerulonephritis) - Light microscopy often shows focal segmental proliferative glomerulonephritis (hence differential diagnosis depends on the immunofluorescence pattern)
Characteristics of rapidly progressive glomerulonephritis
- Rapid development of anuria/severe oliguria with a rise in serum creatinine over 3 months or less
- Light microscopy exhibits crescents in >50% of glomeruli (thus aka crescenteric glomerulonephritis)
Causes of rapidly progressive glomerulonephritis
- Type 1 (anti-glomerular basement membrane Abs)
- Goodpasture syndrome - Type 2 (immune complex)
- Post-streptococcal glomerulonephritis
- Systemic lupus erythematosus
- Henoch-Schonlein purpura - Type 3 (pauci-immune)
- ANCA-associated
- Systemic vasculitis (Wegener granulomatosis, microscopic polyangiitis)
Clinical features of rapidly progressive glomerulonephritis
- Shares common etiologies with nephritic syndrome
- Results in acute renal failure
- Exclude other causes of acute renal failure:
- Prerenal causes: shock, renal hypoperfusion
- Renal causes: acute tubular necrosis, tubulointerstitial nephritis
- Postrenal causes: urinary tract obstruction
Characteristics of microscopic hematuria
- Hematuria not visible to the naked eye
- Detectable only by urinalysis - Usually some degree of hematuria
- Below nephrotic range - Absence of:
- Change in urine volume
- Hypertension
- Azotemia
Causes of microscopic hematuria
- Usually milder forms of proliferative GNs
- IgA nephropathy
- Thin basement membrane syndrome
Clinical features of microscopic hematuria
Always exclude lower urinary tract causes of hematuria in differential diagnosis:
- Trauma, tumour, infections, stones
4 stages of progression in chronic renal failure
- Diminished renal reserve
- GFR = 50% of normal
- Normal serum creatinine & blood urea nitrogen
- Asymptomatic - Renal insufficiency
- GFR = 20-50% of normal
- Azotemia appears
- Anemia, hypertension, polyuria, nocturia - Chronic renal failure
- GFR < 20-25% of normal
- Overt uremia (azotemia + GI, neurological & cardiovascular complications)
- Edema, metabolic acidosis, hyperkalemia - End-stage renal diseases
- GFR < 5% normal
Characteristics of chronic renal failure
- Change in urine volume
- Initial polyuria as tubules cannot concentrate glomerular filtrate
- Terminal oliguria when little functioning nephrons are left - Consequences of decreased filtration
- Hypertension & edema
- Uremia (azotemia + a constellation of signs such as uremic gastroenteritis, uremic fibrinous pericarditis, peripheral neuropathy etc)
- Metabolic derangements (hyperkalemia, metabolic acidosis) - Decreased endocrine functions of kidney
- Anemia (decreased erythropoietin production)
- Secondary hyperparathyroidism (due to decreased Vitamin D activation by renal tubules leading to hypocalcemia)
Causes of renal failure
- Chronic glomerulonephritis (one of the possible outcomes of glomerular diseases presenting as nephritic syndrome)
- Tubulointerstitial diseases
- Chronic pyelonephritis
Pathogenesis of Antibody-Mediated Mechanisms resulting in glomerular injury
- In-situ formation of immune complexes
- Against native antigen
i. Goodpasture disease
- Against planted antigen that localizes in glomerulus
i. HBV, HCV, Streptococcus, syphilis, malaria - Circulating immune complex deposition in glomerulus
- Small circulating immune complexes that are formed elsewhere filtered through glomerulus & ending up lodged within it - Anti-neutrophil cytoplasmic antibodies (ANCA)
- Interacts with neutrophils within glomeruli
Pathogenesis of other pathogenic factors (apart from antibody-mediated mechanisms) that can result in glomerular injury
- Activation of alternative complement pathway (i.e. no
antibodies required)
- Seen in membranoproliferative glomerulonephritis
type II (aka dense deposit disease) - Platelets
- Aggregate in glomeruli during immune-mediated injury, can subsequently release eicosanoids & growth factors which promotes inflammation & cellular proliferation - Coagulation system
- Leakage of fibrin through damaged GBM into Bowman’s space induces proliferation of the parietal layer of Bowman’s capsule (forms crescents) - Cytokines
- Angiotensin
- Podocyte-released cytokines
Role of podocytes in the pathogenesis of glomerular injury
- Podocyte injury results in cytokine release
- TGFbeta, VEGF, PDGF
- Results in local proliferation & fibrosis - Podocytes do not normally regenerate after being injured
- Remaining pool of podocytes become abnormally stretched to maintain an appropriate filtration barrier or become unable to cover some portions of the GBM
- Results in abnormal protein filtration (leading to proteinuria) & segmental loop dilation of the glomerular capillaries (due to incompletely opposed intracapillary pressures)
Etiology & pathogenesis of minimal change disease
Postulated immune-mediated podocyte injury
Clinical presentation of minimal change disease
Nephrotic syndrome
- Usually selective proteinuria (mostly albumin)
- Most common cause of childhood nephrotic syndrome (good prognosis, typically responsive to steroid treatment)
Renal biopsy of minimal change disease
- Light microscopy: Normal
- Immunofluorescence: No immune deposits
- Electron microscopy: Effacement of podocyte foot processes
Etiology & pathogenesis of focal segmental glomerulosclerosis
- Progression from minimal change disease (controversial)
2. Secondary causes
Clinical presentation in focal segmental glomerulosclerosis
- Nephrotic syndrome
- Non-selective proteinuria
- Poor response to steroid therapy - Many progress to chronic renal failure
- Higher incidence of decreased GFR, hematuria & hypertension than minimal change disease
Renal biopsy of focal segmental glomerulosclerosis
- Light microscopy: Focal segmental glomerular sclerosis & hyalinosis
- Immunofluorescence: Focal IgM & C3
- Electron microscopy: Effacement of podocyte foot processes
Etiology & pathogenesis of membranous glomerulopathy
- Idiopathic primary cause
2. Secondary causes (10-20% of cases)
Clinical presentation in membranous glomerulopathy
- Nephrotic syndrome
- Non-selective proteinuria
- Most common cause of nephrotic syndrome in adults (resistant to steroid treatment) - Unpredictable behaviour
- Less than half progress to renal failure
Renal biopsy of membranous glomerulopathy
- Light microscopy:
- Diffuse basement membrane thickening
- Spikes or string of pearl appearance with silver stain (due to protrusions of growth of GBM between subepithelial deposits) - Immunofluorescence: Granular IgG & C3
- Electron microscopy: Subepithelial deposits
Etiology & associations of membranoproliferative glomerulonephritis type I
Idiopathic (postulated to be due to planted HBV & HCV antigens, associated with chronic antigenemia)
Clinical presentation in membranoproliferative glomerulonephritis type I
- Nephrotic or nephritic
2. Associated with decrease in serum C3 levels
Renal biopsy of membranoproliferative glomerulonephritis type I
- Light microscopy:
- Mesangial & endocapillary proliferation, giving glomeruli an accentuated lobulated appearance
- Double contour appearance with silver stain (due to growth of new basement membrane after separation of endothelium from GBM by subendothelial deposits) - Immunofluorescence: IgG, C3
- Electron microscopy: Subendothelial deposits
Etiology & pathogenesis of membranoproliferative glomerulonephritis type II (dense deposit disease)
Activation of alternative complement pathway
Clinical presentation in membranoproliferative glomerulonephritis type II (dense deposit disease)
- Hematuria, chronic renal failure
- High incidence of recurrence in renal transplants
- Associated with decrease in serum C3 levels
Renal biopsy in membranoproliferative glomerulonephritis type II (dense deposit disease)
- Light microscopy: Similar to MPGN type I
- Immunofluorescence: C3
- Electron microscopy: Dense deposits in basement membrane
Etiology & pathogenesis of post-streptococcal glomerulonephritis
Follows infection by nephritogenic strains of Streptococci (classically S. pyogenes) of the throat
- 1-4 weeks after pharyngitis, in 6-10 year olds
- Due to planted antigen in glomerulus
Clinical presentation in post-streptococcal glomerulonephritis
- Nephritic syndrome
- Almost always resolves
- Small minority will develop RPGN
- Rarely, might progress to chronic renal failure - Associated with decrease in serum C3 levels & rise in anti-streptolysin O (ASO) titres
Renal biopsy of post-streptococcal glomerulonephritis
- Light microscopy:
- Diffuse endocapillary proliferation & leukocytic infiltration
- Red cell casts seen in tubules - Immunofluorescence: Granular IgG, C3
- Electron microscopy: Subepithelial humps of electron dense deposits
Etiology & pathogenesis of goodpasture disease
Autoantibodies produced against Goodpasture antigen (NC1 non collagenous domain of the alpha3 chain of type IV collagen)
- Type IV collagen is found in the basement membrane of the glomerulus & alveolus
Clinical presentation of goodpasture disease
- Rapidly progressive glomerulonephritis
- Can lead to acute renal failure - Often associated with pulmonary hemorrhage
- As alveolar basement membrane is attacked too
Renal biopsy of goodpasture disease
- Light microscopy: Crescents
- Immunofluorescence: Linear IgG, C3
- Electron microscopy: Disruption of basement membrane
Etiology & pathogenesis of diabetic nephropathy
Advance glycosylated end-products in longstanding hyperglycemia
Clinical presentation in diabetic nephropathy
Proteinuria (nephrotic range in later stages)
- Often ends up in chronic renal failure
Renal biopsy in diabetic nephropathy
- Light microscopy:
- Kimmelstiel-Wilson lesions (nodular glomerulosclerosis – PAS-positive nodules of matrix situated in the periphery of glomeruli)
- Other associated lesions (pyelonephritis sometimes with papillary necrosis, large vessel atherosclerosis) - Immunofluorescence:
- No immune complex deposition - Electron microscopy:
- Increased basement membrane thickness
- Increased in mesangial matrix
Etiology & pathogenesis of IgA nephropathy (Berger disease)
- Associated with pharyngitis (synpharyngitic GN)
2. Most common cause of glomerulonephritis
Clinical presentation in IgA nephropathy (Berger disease)
- Microscopic proteinuria with hematuria
- Clinical course waxes & wanes, often associated with
upper respiratory tract infections - Less than half progress to renal failure
Renal biopsy of IgA nephropathy (Berger disease)
- Light microscopy: Focal mesangial proliferation
- Immunofluorescence: IgA in mesangium
- Electron microscopy: Mesangial dense deposits
Etiology & pathogenesis of lupus nephritis
Systemic lupus erythematosus
- 70% of SLE patients will develop renal disease
Clinical presentation of lupus nephritis
Any clinical presentation possible
- Aggressive forms typically present with nephritic syndrome & are associated with proliferative changes
- Those presenting with nephrotic syndrome are associated with membranous change
Renal biopsy of lupus nephritis
- Light microscopy:
- Class I: normal
- Class IIa: normal
- Class IIb: mesangial proliferation
- Class III: focal proliferations
- Class IV: diffuse proliferations
- Class V: membranous change - Immunofluorescence:
- Full house pattern (2 complements + 3 Igs): C1q, C3, IgG, IgA, IgM - Electron microscopy:
- Variable
Etiology & pathogenesis of Alport syndrome
X-linked recessive genetic condition involving mutations in the alpha3, alpha4 or alpha5 chains of type IV collagen
- Hence type IV collagen in the affected individual is defective, lacking normal cross-linking
- Type IV collagen required for glomerular basement membrane, lens & cochlea
Clinical presentation in Alport syndrome
- Hematuria +/- proteinuria with progression to chronic renal failure
- Other associated conditions (usually seen in male):
- Deafness
- Lens discolouration
- Posterior cataracts
- Corneal dystrophy
Renal biopsy of Alport syndrome
- Light microscopy:
- Normal initially
- Mesangial cell proliferation and sclerosis - Immunofluorescence:
- Absence of the type IV collagen alpha-3, alpha-4, and/or alpha-5 chains in the basement membrane - Electron microscopy:
- Splitting and alternating irregular thickening and thinning of the glomerular basement membrane (“basket-weave appearance”)
Etiology & pathogenesis of thin membrane disease (benign familial hematuria)
Hereditary condition, unclear inheritance pattern
Clinical presentation of thin membrane disease (benign familial hematuria)
- Recurrent hematuria
- Typically benign clinical course - Unlike Alport syndrome, has no hearing loss, ocular
abnormalities or family history of renal failure)
Renal biopsy of benign familial hematuria
- Light microscopy:
- Normal - Immunofluorescence:
- No immune complex deposition - Electron microscopy:
- Diffuse thinning of the lamina densa of the GBM (to 150-250nm, normal = 300-400nm)
Etiology & pathogenesis of amyloidosis
- Plasma cell dyscrasia (AL amyloid)
2. Chronic inflammatory diseases or neoplasms (AA amyloid)
Clinical presentation in amyloidosis
Proteinuria, often nephrotic range
Renal biopsy of amyloidosis
- Light microscopy:
- Extracellular accumulation of fibrillary proteins (with Congo red stain)
- Apple green birefringence under polarized light microscopy - Immunofluorescence:
- No immune complex deposition - Electron microscopy:
- Variable
