General Pathology Practice Questions

Q: Mutation in Marfan's syndrome is associated with which gene?

Fibrillin I. **Explanation:** **Marfan’s Syndrome** is an autosomal dominant disorder of connective tissue caused by a mutation in the **FBN1 gene** located on chromosome **15q21**. This gene encodes **Fibrillin-1**, a glycoprotein that serves as a major structural component of extracellular microfibrils. These microfibrils form a scaffold for the deposition of elastin and are essential for maintaining the structural integrity of tissues such as the aortic wall, skeletal system, and the suspensory ligaments of the lens. **Analysis of Options:** * **Fibrillin-1 (Correct):** Mutations lead to mechanical weakness of connective tissues and excessive activation of **TGF-β**, which contributes to the clinical manifestations (e.g., aortic root dilation) [1]. * **Collagen I:** Mutations here are associated with **Osteogenesis Imperfecta** (brittle bone disease) and certain types of Ehlers-Danlos Syndrome. * **Collagen IV:** This is a key component of the basement membrane; mutations are associated with **Alport Syndrome**. * **Fibrillin-2:** Mutations in the FBN2 gene (chromosome 5) cause **Congenital Contractural Arachnodactyly** (Beals Syndrome), which mimics Marfan’s but lacks the cardiac and ocular complications. **Clinical Pearls for NEET-PG:** 1. **Skeletal:** Dolichostenomelia (long limbs), arachnodactyly (long fingers), and pectus excavatum [1]. 2. **Ocular:** **Ectopia lentis** (dislocation of the lens), typically **upward and outward** (superior-temporal). 3. **Cardiovascular:** The most life-threatening complication is **Aortic Dissection** preceded by cystic medial necrosis. Mitral Valve Prolapse (MVP) is also common [1]. 4. **Diagnostic Sign:** Steinberg sign (thumb sign) and Walker-Murdoch sign (wrist sign). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 153-154.

Q: What is the initiating mechanism in endotoxic shock?

Endothelial injury. The initiating event in endotoxic (septic) shock is **Endothelial injury**. Endotoxic shock is primarily triggered by **Lipopolysaccharide (LPS)**, a component of the cell wall of Gram-negative bacteria [2]. 1. **Why Endothelial Injury is Correct:** When LPS enters the bloodstream, it binds to Lipopolysaccharide-binding protein (LBP) and interacts with **CD14 and TLR-4 receptors** on macrophages and endothelial cells. This triggers a massive release of inflammatory cytokines (TNF-α, IL-1) [3]. These mediators cause direct damage to the vascular endothelium [1]. This injury exposes the subendothelial collagen, activating the coagulation cascade (leading to DIC) and causing the release of nitric oxide (NO), which is the primary driver of the subsequent systemic effects. 2. **Why Other Options are Incorrect:** * **Peripheral vasodilation (A):** This is a *result* of the endothelial injury and the release of potent vasodilators like Nitric Oxide. * **Increased vascular permeability (C):** This occurs *after* endothelial injury and activation [1]. The "leaky" capillaries lead to edema and hypovolemia, but this is a secondary structural consequence. * **Reduced cardiac output (D):** In the early (hyperdynamic) phase of septic shock, cardiac output is actually **increased**. **High-Yield Clinical Pearls for NEET-PG:** * **Key Mediator:** **TNF-α** is the primary cytokine mediator of septic shock [3]. * **Receptor:** **TLR-4** (Toll-like receptor 4) is the specific pattern recognition receptor for LPS. * **Nitric Oxide (NO):** Produced by inducible Nitric Oxide Synthase (iNOS) in response to cytokines, it is responsible for the characteristic hypotension. * **Warm Shock:** Septic shock is initially a "warm shock" due to peripheral vasodilation, unlike hypovolemic or cardiogenic shock.

Q: Iron in tissues is stained with which of the following stains?

Prussian Blue. **Explanation:** **Prussian Blue (Perls' Stain)** is the correct answer because it is the gold-standard histochemical stain used to detect **ferric iron (Fe³⁺)** in tissues [1]. The underlying chemical principle involves the reaction of ferric iron with potassium ferrocyanide in an acidic medium, resulting in the formation of a bright blue pigment called ferric ferrocyanide (Prussian Blue). This stain is primarily used to visualize iron stored in the form of **hemosiderin** within macrophages (siderophages) or parenchymal cells [1]. **Analysis of Incorrect Options:** * **Sudan O (Sudan III/IV):** These are lipid-soluble dyes used to stain **neutral fats (lipids)** and triglycerides. They are commonly used on frozen sections to diagnose fat embolism or steatosis. * **PAS (Periodic Acid-Schiff):** This stain detects **glycogen** and mucopolysaccharides. It is widely used to visualize basement membranes, fungal walls, and glycogen storage diseases. **Clinical Pearls for NEET-PG:** * **Hemochromatosis vs. Hemosiderosis:** Prussian Blue is essential for grading iron overload in the liver and heart [1]. * **Sideroblastic Anemia:** This stain identifies "Ringed Sideroblasts" in the bone marrow (iron-laden mitochondria surrounding the nucleus). * **Heart Failure Cells:** In chronic passive congestion of the lungs, Prussian Blue identifies hemosiderin-laden macrophages in the alveoli. * **Note:** It does **not** stain iron in hemoglobin or ferritin directly; it specifically targets the insoluble hemosiderin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 854-855.

Q: A ring chromosome is a result of which chromosomal abnormality?

Deletion. **Explanation:** A **ring chromosome** is a structural chromosomal abnormality that occurs when a chromosome undergoes **terminal deletions** at both the short (p) and long (q) arms. Following the loss of these distal segments, the remaining "sticky" ends of the central portion fuse together to form a ring shape. Because the formation of a ring chromosome necessitates the loss of genetic material from the telomeric regions, it is fundamentally a result of **deletion**. **Analysis of Options:** * **A. Deletion (Correct):** As described, the breakage of both ends of a chromosome followed by fusion is the mechanism. The resulting loss of genetic material often leads to clinical phenotypes (e.g., Ring 20 syndrome). * **B. Inversion:** This involves a single chromosome undergoing two breaks, with the intervening segment rotating 180° and reinserting. There is no loss of genetic material (balanced). * **C. Duplication:** This refers to the presence of an extra copy of a segment of a chromosome. * **D. Translocation:** This involves the exchange of segments between non-homologous chromosomes (e.g., Robertsonian or Reciprocal translocations). **High-Yield NEET-PG Pearls:** * **Karyotype Notation:** A ring chromosome is denoted by the symbol **'r'** (e.g., 46,XX,r(15)). * **Clinical Significance:** Ring chromosomes are often unstable during mitosis, leading to mosaicism [2]. * **Common Example:** **Ring 14 syndrome** (characterized by seizures and intellectual disability) and **Ring X** (a variant of Turner Syndrome) [1]. * **Telomeres:** Normally, telomeres prevent end-to-end fusion; ring formation only occurs when telomeres are lost via deletion. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 175-177. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169.

Question 1

Myasthenia gravis is caused by dysfunction of -

Accepted Answer

Thymus gland

Answer

Pineal gland

Answer

Pituitary gland

Answer

Parathyroid gland

Question 2

Which of the following statements about amyloidosis is false?

Accepted Answer

It is made of proteins that calcify.

Answer

It can be a complication of chronic infections.

Answer

It is associated with extracellular eosinophilic hyaline material.

Answer

It shows apple-green birefringence under polarized light.

Question 3

A 40-year-old female presented with acute painful swelling of the left leg. Ultrasound of the left leg showed deep venous thrombosis. Which of the following abnormalities is least likely to be involved in this condition?

Accepted Answer

Hypohomocysteinemia

Answer

Factor V Leiden mutation

Answer

Prothrombin gene mutation

Answer

Protein C deficiency

Question 4

Mutation in Marfan's syndrome is associated with which gene?

Accepted Answer

Fibrillin I

Answer

Collagen I

Answer

Collagen IV

Answer

Fibrillin II

Question 5

What is the initiating mechanism in endotoxic shock?

Accepted Answer

Endothelial injury

Answer

Peripheral vasodilation

Answer

Increased vascular permeability

Answer

Reduced cardiac output

Question 6

Senescent cells are deficient in which enzyme?

Accepted Answer

Telomerase

Answer

RNA polymerase

Answer

DNA polymerase

Answer

Helicase

Question 7

A tissue preparation is experimentally subjected to a hypoxic environment. The cells in this tissue begin to swell, and chromatin begins to clump in cell nuclei. ATPases are activated, and ATP production decreases. Which of the following ions accumulating in mitochondria and the cytosol contributes most to these findings and to eventual cell death?

Accepted Answer

Ca2+

Answer

Cl-

Answer

HCO3-

Answer

K+

Question 8

Iron in tissues is stained with which of the following stains?

Accepted Answer

Prussian Blue

Answer

Sudan O

Answer

PAS

Answer

None of the above

Question 9

A ring chromosome is a result of which chromosomal abnormality?

Accepted Answer

Deletion

Answer

Inversion

Answer

Duplication

Answer

Translocation

Question 10

An embolus which passes through an arteriovenous communication and enters the systemic circulation is called?

Accepted Answer

Paradoxical embolus

Answer

Retrograde embolus

Answer

Saddle embolus

Answer

Atheroembolus

General Pathology — MCQs

General Pathology — MCQs

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