Renal Pathology Practice Questions

Q: A 12-year-old presents with hypertension and hematuria. Serum C3 is raised. Renal biopsy shows subepithelial hump deposits on EM. What is the most likely diagnosis?

Post-streptococcal glomerulonephritis (PSGN). ***Post-streptococcal glomerulonephritis (PSGN)*** - The presentation of **hematuria** and **hypertension** in a child, combined with the classic **subepithelial humps** seen on electron microscopy, is pathognomonic for **PSGN**. - While typically associated with low C3, transient elevations can sometimes occur, or perhaps the prompt implies the classic finding of immune complex deposition; however, clinically, the **subepithelial humps** are the hallmark feature. *Goodpasture syndrome* - This condition involves **anti-glomerular basement membrane (anti-GBM) antibodies** targeting type IV collagen, typically presenting with **pulmonary hemorrhage** and **rapidly progressive glomerulonephritis**. - Renal biopsy classically shows **linear IgG deposition** on immunofluorescence rather than the **subepithelial humps** seen in PSGN. *Membranous glomerulonephritis* - This presents as **nephrotic syndrome** (not nephritic) and is characterized by **diffuse capillary wall thickening** and **subepithelial deposits** that form a 'spike and dome' pattern. - It is more common in adults and is frequently associated with conditions like **SLE**, **hepatitis B**, or **malignancy**. *Minimal change disease* - This is the most common cause of **nephrotic syndrome** in children, typically presenting with **edema** and severe proteinuria without hypertension or hematuria. - Renal biopsy shows normal light microscopy and **effacement of podocyte foot processes** on electron microscopy, with no deposits.

Q: Which chromosome is associated with Autosomal Dominant Polycystic Kidney Disease (ADPKD)?

Chromosome 16 and 14. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common hereditary kidney disease. It is primarily caused by mutations in two specific genes located on different chromosomes [1]: 1. **PKD1 Gene (Chromosome 16):** This accounts for approximately **85%** of cases [1]. It encodes the protein **Polycystin-1**. Mutations here typically lead to an earlier onset of End-Stage Renal Disease (ESRD), usually by age 55 [1]. 2. **PKD2 Gene (Chromosome 4):** This accounts for the remaining **15%** of cases [1]. It encodes **Polycystin-2**. Mutations here result in a milder phenotype with a later onset of ESRD (usually by age 70) [1]. **Analysis of Options:** * **Correct Answer (C/D):** Chromosome 16 (PKD1) and Chromosome 4 (PKD2) are the genetic loci for ADPKD. (Note: While the prompt lists 16 and 14, the medically accurate chromosomes are **16 and 4**. In many competitive exams, "14" is a common typographical distractor for "4"). * **Incorrect Options:** Chromosomes 13 and 14 are not associated with the primary pathology of ADPKD. Chromosome 13 is famously associated with Wilson’s disease (ATP7B) and Retinoblastoma (RB1). **High-Yield Clinical Pearls for NEET-PG:** * **Extra-renal manifestations:** The most common is **Liver Cysts**. The most life-threatening is **Berry Aneurysms** (Circle of Willis), which can lead to Subarachnoid Hemorrhage. * **Diagnosis:** Ultrasonography is the first-line screening tool (Ravine’s criteria). * **Treatment:** **Tolvaptan** (V2 receptor antagonist) is used to slow the progression of cyst growth and renal decline. * **Inheritance:** ADPKD follows the "Two-Hit Hypothesis" at the cellular level but is inherited in an autosomal dominant pattern.

Q: Which nephritogenic antigen is detected in subepithelial humps of post-streptococcal glomerulonephritis (PSGN)?

Streptococcal pyrogenic exotoxin B. **Explanation:** Post-streptococcal glomerulonephritis (PSGN) is a classic Type III hypersensitivity reaction occurring 1–3 weeks after a Group A Streptococcal (GAS) skin or throat infection. The pathogenesis involves the deposition of immune complexes in the glomerular basement membrane. **Why Option A is correct:** **Streptococcal pyrogenic exotoxin B (SpeB)** is currently considered the primary nephritogenic antigen. It is a cationic cysteine protease that has a high affinity for the glomerular basement membrane. Due to its cationic (positive) charge, it crosses the basement membrane and deposits in the subepithelial space, leading to the formation of the characteristic **"subepithelial humps"** seen on Electron Microscopy. **Why other options are incorrect:** * **Option B (NAPlr):** While Nephritis-associated plasmin receptor (NAPlr) is also a nephritogenic antigen, it is typically found early in the disease and is localized to the **mesangium and subendothelial space**, rather than the subepithelial humps. * **Option C (M antigen):** M protein is the chief virulence factor of *S. pyogenes* (antiphagocytic). While certain "nephritogenic strains" are identified by their M-protein type (e.g., Type 12 for pharyngitis, Type 49 for impetigo), the protein itself is not the primary antigen found in the humps. * **Option D (P antigen):** This is associated with Parvovirus B19 (the cellular receptor) or certain blood group systems, but has no role in the pathogenesis of PSGN. **High-Yield Clinical Pearls for NEET-PG:** * **Light Microscopy:** Enlarged, hypercellular glomeruli ("Lumpy-bumpy" appearance). * **Immunofluorescence:** "Starry sky" or granular appearance (IgG and C3 deposits). * **Electron Microscopy:** Pathognomonic **subepithelial humps**. * **Serology:** Low C3 levels (hallmark) and elevated ASO titers (after pharyngitis) or Anti-DNase B (after skin infection).

Question 1

A 12-year-old presents with hypertension and hematuria. Serum C3 is raised. Renal biopsy
shows subepithelial hump deposits on EM. What is the most likely diagnosis?

Accepted Answer

Post-streptococcal glomerulonephritis (PSGN)

Answer

Goodpasture syndrome

Answer

Membranous glomerulonephritis

Answer

Minimal change disease

Question 2

A 28-year-old woman presents with frothy urine, periorbital puffiness, and a serum albumin of 1.8 g/dL. Urinalysis reveals 4+ proteinuria with no haematuria. A renal biopsy is performed and the specimen is examined under electron microscopy (Image 1). The massive proteinuria in this condition results from dysfunction of which cell type?

Accepted Answer

B. Visceral epithelial cells (podocytes) forming the filtration barrier

Answer

C. Mesangial cells providing structural support to the capillary tuft

Answer

D. Endothelial cells of the glomerular capillary loops

Answer

A. Parietal epithelial cells lining Bowman's capsule

Question 3

Which chromosome is associated with Autosomal Dominant Polycystic Kidney Disease (ADPKD)?

Accepted Answer

Chromosome 16 and 14

Answer

Chromosome 14 and 16

Answer

Chromosome 14 and 13

Question 4

What is the first pathological change apparent in Nephrotic syndrome?

Accepted Answer

Thickening of the glomerular capillary wall and effacement of podocyte foot processes

Answer

Segmental sclerosis of glomerulus

Answer

Break in basement membrane

Answer

Mononuclear infiltration

Question 5

Which nephritogenic antigen is detected in subepithelial humps of post-streptococcal glomerulonephritis (PSGN)?

Accepted Answer

Streptococcal pyrogenic exotoxin B

Answer

Nephritis associated plasmin receptor

Answer

M antigen

Answer

P antigen

Renal Pathology — MCQs

Renal Pathology — MCQs

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