Renal Pathology: Exam questions and Answers

1. A 10 year old female presented with sudden onset hematuria with oliguria. Urine examination- RBC++, RBC casts+, Protein+.

a) Probable diagnosis?
b) Discuss the etiopathogenesis and classification of the disease
c) Mention the morphological features of the target organ
d) Laboratory diagnosis of the disease

a) Probable diagnosis?

Acute Nephritic Syndrome – Most probably Acute Post-Infectious Glomerulonephritis (Post-Streptococcal Glomerulonephritis)

• Differential Diagnosis:
  • IgA Nephropathy
  • Rapidly Progressive Glomerulonephritis- low chance
  • Lupus Nephritis- low probability

B)

Etiology

Nephritogenic Strains of Group A β-Hemolytic Streptococci

Other organisms: Pneumococcus, staphylococcus, viral infections (mumps, measles, chickenpox etc.)

Pathogenesis

Classification of Nephritic Syndromes

1️⃣ Infectious/Post-Infectious Glomerulonephritis

• Acute Post-Streptococcal Glomerulonephritis (PSGN)
• Non-Streptococcal Post-Infectious GN
  • Staphylococcal endocarditis-associated GN
  • Hepatitis B/C-related GN
  • Malaria-associated GN

2️⃣ Primary Glomerular Diseases (Idiopathic)

• IgA Nephropathy (Berger’s Disease)
• Membranoproliferative Glomerulonephritis (MPGN)

3️⃣ Autoimmune & Systemic Diseases (Secondary GN)

• Systemic Lupus Erythematosus (Lupus Nephritis – Class III & IV)
• Henoch-Schönlein Purpura (IgA Vasculitis)

4️⃣ Hereditary Nephritic Syndromes

• Alport Syndrome
• Thin Basement Membrane Disease (Benign Familial Hematuria)

5️⃣ Rapidly Progressive (Crescentic) Glomerulonephritis (RPGN)

• Type I (Anti-GBM Disease) – Goodpasture Syndrome
• Type II (Immune Complex) – PSGN, Lupus Nephritis, IgA Nephropathy
• Type III (Pauci-immune GN) – ANCA-associated Vasculitis

C) Morphology

Gross: Symmetrically enlarged kidneys
Petechial hemorrhages- Flea-bitten kidney

Diagram:

Light microscopy: Glomerulus is hypercellular (Diffuse Glomerulonephritis).

Diagram:

Immunofluorescence: Granular deposits of IgG and complement

Electron microscopy: Subepithelial deposits (“Humps”)

d) Laboratory Diagnosis of Acute Post-Streptococcal Glomerulonephritis

1️⃣ Urine Examination

• Oliguria
• RBC+++ → Microscopic or gross hematuria
• RBC Casts +
• Mild Proteinuria

2️⃣ Blood Tests

• Elevated Serum Urea & Creatinine
• Low Serum Complement (C3) → Hypocomplementemia

3️⃣ Streptococcal Serology

• ASO Titre (Anti-Streptolysin O Antibody) → Raised in post-pharyngitis cases
• Anti-DNase B → More reliable in post-impetigo cases

4️⃣ Microscopic Findings (Renal Biopsy)

• Light Microscopy → Diffuse glomerular hypercellularity
• Immunofluorescence (IF) → Granular deposits of IgG and C3
• Electron Microscopy → Subepithelial humps (Immune complex deposits)