Nephrotic Syndrome

Nephrotic syndrome is classically defined as a triad of

Overt proteinuria (>3.5g/24h or 1 g/m^2 per 24 hours)
hypoalbuminaemia (< 30 g/l)
oedema

Possible intravascular volume depletion with hypotension or intravascular expansion with hypertension

Other features include hyperlipidaemia, a hypercoagulable state (due to loss of antithrombin III) and a predisposition to infection (due to loss of immunoglobulins)

In children the peak incidence is between 2 and 5 years of age. Around 80% of cases in children are due to a condition called minimal change glomerulonephritis. The condition generally carries a good prognosis with around 90% of cases responding to high-dose oral steroids.

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Nephrotic syndrome + anti-PLA2R antibodies → idiopathic membranous nephropathy

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Membranous GN

Pulmonary-renal Syndromes

Diagnosis	Key Clinical Features	Primary Serology	Renal Biopsy Findings
GPA (Wegener’s)	Saddle nose, sinusitis, lung nodules/hemorrhage	c-ANCA (PR3-positive)	Pauci-immune crescentic GN
EGPA (Churg-Strauss)	Asthma, eosinophilia, mononeuritis multiplex	p-ANCA (MPO-positive)	Pauci-immune crescentic GN
Goodpasture’s	Isolated lung hemorrhage + renal failure	Anti-GBM antibodies	Linear IgG deposition
MPA	Similar to GPA but no granulomas/upper airway involvement	p-ANCA (MPO-positive)	Pauci-immune crescentic GN

Rule of thumb based on Renal Biopsy

Linear Immunofluorescence (IF)? * Yes: It is Goodpasture’s Syndrome (Anti-GBM disease).
Pauci-immune (Negative IF)?
- This indicates an ANCA-associated vasculitis. Look at the extra-renal symptoms:
  - Asthma/Eosinophilia? → EGPA (Churg-Strauss).
  - Sinusitis/Nose deformity/Nodules? → GPA (Wegener's).
  - None of the above? → MPA (Microscopic Polyangiitis).

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