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PA27.5-6 | Glomerular Diseases — Summary & Reflection

REFLECT

A 35-year-old woman with a 10-year history of Type 2 diabetes and hypertension now has 4 g/day of proteinuria and creatinine of 2.1 mg/dL. She also mentions noticing frothy urine for 6 months. Her ophthalmologist has previously documented background diabetic retinopathy.

Before you read further — take 3 minutes to:
1. Identify the syndrome (nephrotic or nephritic?) and state your reasoning.
2. List TWO glomerular diseases you would include in your differential, given her background.
3. Specify what finding on renal biopsy LM would be pathognomonic for one of them.
4. Decide whether you would recommend a renal biopsy in this patient. Justify in one sentence.

Write your answers before checking. Self-assessment after: What did you miss? What did you reason correctly?

KEY TAKEAWAYS

Core principles of this module:

  1. Four mechanisms of glomerular injury: in-situ IC (granular IF), circulating IC (granular IF), anti-GBM (linear IF), podocyte injury (negative IF). Complement is consumed by the first three, not the last.
  1. Nephrotic vs Nephritic: proteinuria > 3.5 g/day + oedema + lipiduria = nephrotic; RBC casts + haematuria + hypertension + oliguria = nephritic.
  1. Nephrotic triad by age: MCD (children) → FSGS (adults, poor prognosis) → Membranous NP (adults, PLA2R, spikes/domes).
  1. PSGN hallmarks: latent period 1-3 weeks, subepithelial humps on EM, lumpy-bumpy IF, low C3, self-limiting in children.
  1. RPGN types I/II/III: memorise IF (linear / granular / negative) + serology (anti-GBM / variable / ANCA).
  1. IgA nephropathy (PA27.6): commonest GN worldwide; synpharyngitic haematuria (simultaneous with infection); normal complement; dominant mesangial IgA on IF; mesangial deposits on EM; HSPN is the systemic form. Oxford MEST-C score for prognosis.
  1. The diagnostic triad (LM + IF + EM) is the gold standard for all glomerular diseases — each modality adds a dimension: LM shows structure, IF shows immune deposits, EM shows ultra-fine deposit location.