Question
A 10-year-old female presented with sudden onset of hematuria and oliguria. Urine examination shows presence of RBC, casts and mild proteinuria.
- (a) What is your probable diagnosis 2 mark(s)
- (b) Discuss etiopathogenesis and classification of the disease 6 mark(s)
- (c) Mention the morphological features of the target organ 4 mark(s)
- (d) Laboratory diagnosis of the disease 3 mark(s)
Answer
(a) Probable diagnosis: Acute glomerulonephritis (nephritic syndrome) — presenting with the classic nephritic triad of haematuria (with RBC casts, indicating glomerular bleeding), oliguria, and mild proteinuria; likely acute post-streptococcal glomerulonephritis given the age group, though the vignette does not specify an antecedent infection.
(b) Aetiopathogenesis and classification: Aetiopathogenesis: Most cases of acute nephritic syndrome are immune-mediated glomerular injury — either (i) in-situ immune complex formation (antigen planted in the glomerulus, e.g., post-streptococcal antigens, followed by antibody binding) or (ii) deposition of circulating immune complexes in the glomerular capillary walls/mesangium. Complement activation follows, recruiting neutrophils and monocytes that damage the glomerular capillary wall, reducing GFR (causing oliguria and azotaemia) and allowing red cells to leak into the urinary space (haematuria).
Classification (of glomerulonephritis presenting with nephritic syndrome):
- Acute post-infectious (post-streptococcal) GN
- IgA nephropathy (Berger disease)
- Hereditary nephritis (Alport syndrome)
- Rapidly progressive (crescentic) GN — anti-GBM disease, immune complex-mediated, pauci-immune (ANCA-associated)
- Membranoproliferative GN (can show a nephritic/mixed picture)
(c) Morphological features of the kidney (target organ):
- Diffusely enlarged, hypercellular glomeruli due to endothelial and mesangial cell proliferation with neutrophilic infiltration (in post-streptococcal GN).
- Immunofluorescence: granular (“lumpy-bumpy”) deposits of IgG and C3 along the capillary walls and mesangium.
- Electron microscopy: subepithelial electron-dense “humps.”
- In crescentic GN: crescents (proliferating parietal epithelial cells and infiltrating monocytes) in Bowman’s space.
(d) Laboratory diagnosis:
- Urinalysis: haematuria with dysmorphic RBCs, RBC casts (pathognomonic of glomerular bleeding), sub-nephrotic proteinuria.
- Renal function tests: elevated blood urea and serum creatinine.
- Serum complement (C3) — low in post-streptococcal GN and lupus nephritis, normal in IgA nephropathy and anti-GBM disease.
- ASO titre (anti-streptolysin O) — elevated in post-streptococcal GN.
- ANA, anti-dsDNA (for lupus), ANCA, anti-GBM antibody as indicated.
- Renal biopsy with light microscopy, immunofluorescence, and electron microscopy — definitive diagnosis.