General Pathology Practice Questions

Q: Periodic acid-Schiff (PAS) stain does not typically stain which of the following?

Lipids. **Explanation:** The **Periodic acid-Schiff (PAS)** stain is a histochemical technique used to detect structures rich in **polysaccharides** (carbohydrates). **Mechanism:** Periodic acid acts as an oxidizing agent that breaks the carbon-carbon bonds between 1,2-glycols, converting them into **aldehydes**. These aldehydes then react with the **Schiff reagent** to produce a characteristic magenta/bright pink color. **Why Lipids are the correct answer:** Lipids (specifically neutral fats and triglycerides) lack the 1,2-glycol groups necessary for this reaction. Therefore, they do not react with PAS and appear clear or empty on the slide. Lipids are typically stained using specialized stains like **Sudan Black B** or **Oil Red O**. **Why the other options are incorrect:** * **Glycogen:** This is a glucose polymer with abundant glycol groups, making it highly PAS-positive. It is the classic example of PAS staining in the liver. * **Fungal cell wall:** The cell walls of fungi contain high concentrations of polysaccharides like **chitin** and glucans, which stain intensely with PAS (used to diagnose Candidiasis or Histoplasmosis). * **Basement membrane:** It is rich in **Type IV collagen** and glycoproteins (sialic acid), which are PAS-positive. This is clinically useful in identifying glomerular basement membrane thickening in renal biopsies. **High-Yield Clinical Pearls for NEET-PG:** * **Diastase Sensitivity:** To confirm if a PAS-positive substance is glycogen, the section is treated with diastase (amylase). If the staining disappears, it is glycogen (**PAS-D test**). * **Whipple’s Disease:** PAS is the stain of choice to identify **Tropheryma whipplei** (PAS-positive macrophages in the lamina propria). * **Erythroleukemia (M6):** PAS positivity is seen in the erythroblasts. * **Alpha-1 Antitrypsin Deficiency:** Characterized by PAS-positive, diastase-resistant globules in hepatocytes.

Question 1

Which of the following is associated with the amyloid pattern seen in hemodialysis?

Accepted Answer

Beta-2-macroglobulin

Answer

AA amyloid

Answer

ATTR amyloid

Answer

AL amyloid

Question 2

What is the commonest type of necrosis?

Accepted Answer

Coagulative

Answer

Fatty

Answer

Caseous

Answer

Liquifactive

Question 3

Progressive cellular damage, including to DNA, can lead to which of the following outcomes?

Accepted Answer

Necrosis or Apoptosis

Answer

Atrophy

Answer

Metaplasia

Answer

Calcification

Question 4

Deficiency of which of the following factors increases the incidence of thrombus formation?

Accepted Answer

Lipoprotein(a)

Answer

Protein C

Answer

Antithrombin III

Answer

Protein S

Question 5

All of the following are associated with increased aging, except?

Accepted Answer

Enlargement of telomere

Answer

Decrease in number of mitochondria

Answer

Glycosylation of DNA

Answer

Glycosylation of RNA

Question 6

Periodic acid-Schiff (PAS) stain does not typically stain which of the following?

Accepted Answer

Lipids

Answer

Fungal cell wall

Answer

Basement membrane of bacteria

Answer

Glycogen

Question 7

All of the following are true about apoptosis except?

Accepted Answer

A 'smeared' pattern of DNA fragmentation

Answer

Expression of caspases

Answer

Internucleosomal cleavage of DNA

Answer

Expression of phosphatidyl serine

Question 8

Fat necrosis occurs in which of the following organs?

Accepted Answer

Omentum

Answer

Brain

Answer

Heart

Answer

Kidney

Question 9

Russell bodies are found in which cell type?

Accepted Answer

Plasma cells

Answer

White blood cells

Answer

Red blood cells

Answer

Mast cells

Question 10

Immune complexes mediate which type of necrosis?

Accepted Answer

Fibrinoid necrosis

Answer

Coagulative necrosis

Answer

Liquefactive necrosis

Answer

Caseous necrosis

General Pathology — MCQs

General Pathology — MCQs

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