General Pathology Practice Questions

Q: What is the Leiden factor?

Factor V. **Explanation:** **Factor V Leiden** is the most common inherited cause of hypercoagulability (thrombophilia) among Caucasians [1]. It is caused by a specific point mutation in the Factor V gene (G1691A), which results in the substitution of arginine by glutamine at position 506 [1]. **Why Option D is Correct:** Under normal physiological conditions, **Activated Protein C (APC)** inactivates Factor Va and Factor VIIIa to limit clot formation. In Factor V Leiden, the mutation alters the cleavage site on Factor V where Protein C normally binds. This renders Factor V resistant to inactivation by APC (**APC Resistance**) [1]. Consequently, Factor V remains active in the circulation for longer periods, leading to a prothrombotic state and increased risk of Venous Thromboembolism (VTE) [1]. **Why Other Options are Incorrect:** * **Factor VI:** This factor does not exist in the modern coagulation cascade (it was previously thought to be an activated form of Factor V). * **Factor VIII:** While Factor VIII is also inactivated by Protein C, the "Leiden" mutation specifically affects Factor V. Deficiencies in Factor VIII lead to Hemophilia A. * **Factor IV:** This refers to Calcium ions ($Ca^{2+}$), which are essential cofactors for several steps in the coagulation cascade but are not associated with the Leiden mutation. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Dominant. * **Clinical Presentation:** Recurrent Deep Vein Thrombosis (DVT) and Pulmonary Embolism [1]. * **Diagnosis:** Suspect in patients with "Activated Protein C Resistance" on screening assays; confirmed by genetic testing (PCR). * **Key Association:** It is a major risk factor for cerebral venous thrombosis in women taking oral contraceptive pills (OCPs). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 133-134.

Q: Keratinizing metaplasia of salivary glands results due to the deficiency of which vitamin?

Vitamin A. **Explanation:** **Vitamin A (Retinol)** is essential for the maintenance of specialized epithelia, particularly the differentiation of mucus-secreting columnar epithelium. When Vitamin A is deficient, these specialized cells undergo **squamous metaplasia**, transforming into a keratinizing stratified squamous epithelium [1]. This process occurs in the salivary glands, respiratory tract, and urinary tract [1]. In the salivary glands, the loss of mucus production and the buildup of keratin debris can lead to ductal obstruction and secondary infections. **Analysis of Incorrect Options:** * **Thiamine (Vitamin B1):** Deficiency primarily leads to Beriberi (Dry/Wet) and Wernicke-Korsakoff syndrome, affecting the cardiovascular and nervous systems, not epithelial differentiation. * **Riboflavin (Vitamin B2):** Deficiency is characterized by cheilosis, glossitis, and corneal neovascularization, but it does not cause keratinizing metaplasia. * **Vitamin E:** Acts as a potent antioxidant protecting cell membranes from lipid peroxidation. Deficiency leads to hemolytic anemia and neurological deficits (spinocerebellar ataxia). **NEET-PG High-Yield Pearls:** * **Metaplasia** is a reversible change where one adult cell type is replaced by another to withstand stress [1]. * **Vitamin A & the Eye:** Deficiency causes Xerophthalmia. The sequence is: Nyctalopia (Night blindness) → Conjunctival xerosis → **Bitot’s spots** (keratin plaques) → Corneal xerosis → Keratomalacia (corneal melting). * **Therapeutic use:** All-trans retinoic acid (ATRA) is used in Acute Promyelocytic Leukemia (M3) to induce cell differentiation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 49.

Q: Which of the following pigments is NOT derived from hemoglobin?

Lipofuscin. ### Explanation The correct answer is **C. Lipofuscin**. **1. Why Lipofuscin is the correct answer:** Lipofuscin is known as the "wear-and-tear" or "aging" pigment. Unlike the other options, it is **not** derived from the breakdown of hemoglobin or iron. Instead, it is a product of **lipid peroxidation** of polyunsaturated fatty acids of subcellular membranes. It represents indigestible material within lysosomes and is typically found in aging cells, particularly in the heart (brown atrophy), liver, and neurons. **2. Why the other options are incorrect:** * **Hematin (Option A):** This is an oxidation product of hemoglobin where the iron atom is converted from the ferrous ($Fe^{2+}$) to the ferric ($Fe^{3+}$) state. It is seen in conditions like malaria (hemozoin). * **Hemosiderin (Option B):** This is an iron-storage complex. When there is an excess of iron (derived from the heme portion of hemoglobin), it is stored as ferritin or aggregates into golden-yellow granules called hemosiderin. * **Bilirubin (Option D):** This is the primary catabolic product of the heme moiety of hemoglobin. After the removal of iron, the protoporphyrin ring is converted into biliverdin and then into bilirubin. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Prussian Blue Stain:** Stains **Hemosiderin** blue (Perls' reaction). It does **not** stain Lipofuscin or Bilirubin. * **Lipofuscin Appearance:** Appears as yellow-brown, finely granular cytoplasmic pigment. It is a marker of past free radical injury. * **Bilirubin Staining:** Best visualized using the **Fouchet stain**. * **Hematoidin:** A hemoglobin-derived pigment chemically similar to bilirubin but formed in tissues (e.g., old infarcts/bruises) in an anaerobic environment; it is iron-free.

Q: Which stain is used to identify Gaucher cells?

Periodic Acid Schiff (PAS). **Explanation:** **Gaucher disease** is the most common lysosomal storage disorder, caused by a deficiency of the enzyme **glucocerebrosidase**. This leads to the accumulation of glucocerebroside (a glycolipid) within the lysosomes of macrophages, transforming them into characteristic **Gaucher cells** [1]. 1. **Why PAS is Correct:** Gaucher cells have a distinct "wrinkled tissue paper" or "crumpled silk" appearance of the cytoplasm [1]. Because the accumulated material is a **glycolipid** (containing carbohydrate moieties), it is strongly **PAS (Periodic Acid Schiff) positive**. This stain highlights the complex carbohydrates within the stored lipid. 2. **Analysis of Incorrect Options:** * **Von Kossa stain:** Used to identify **calcium** deposits (appears black). It is commonly used in conditions like Monckeberg arteriosclerosis or nephrocalcinosis. * **Oil red O:** Used to identify **neutral lipids/triglycerides**. While Gaucher cells contain lipids, the glycolipids are better demonstrated by PAS; Oil red O is typically used on frozen sections for fat emboli or steatosis. * **Sudan Black B:** Primarily used to stain **phospholipids and sterols**. It is a classic stain for identifying myeloblasts in Acute Myeloid Leukemia (AML). **High-Yield Clinical Pearls for NEET-PG:** * **Gaucher Cell Morphology:** Large macrophages with eccentric nuclei and fibrillar, "crumpled silk" cytoplasm [1]. * **Enzyme Marker:** Gaucher cells are also positive for **TRAP (Tartrate-Resistant Acid Phosphatase)**. * **Clinical Triad:** Hepatosplenomegaly, bone involvement (Erlenmeyer flask deformity), and pancytopenia [1]. * **Chitotriosidase:** A plasma marker used to monitor disease activity and response to enzyme replacement therapy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 163.

Q: Which of the following is NOT an inherited coagulation disorder?

Lupus anticoagulant. **Explanation:** The distinction between inherited and acquired thrombophilias is a high-yield topic in NEET-PG. **1. Why Lupus Anticoagulant is the correct answer:** **Lupus Anticoagulant (LA)** is an **acquired** autoimmune condition [1]. It is a type of antiphospholipid antibody (aPL) found in Antiphospholipid Antibody Syndrome (APS). Despite its name, it is a pro-thrombotic agent *in vivo*, leading to venous and arterial thrombosis, though it paradoxically prolongs the Activated Partial Thromboplastin Time (aPTT) *in vitro* [1]. **2. Why the other options are incorrect:** * **Factor V Leiden Mutation (Option C):** This is the **most common inherited cause** of hypercoagulability [1]. It involves a point mutation (G1691A) in the Factor V gene, making Factor V resistant to cleavage by activated Protein C (APC resistance) [1]. * **Protein C and S Deficiencies (Options A & B):** These are **autosomal dominant** inherited disorders. Protein C and S are natural anticoagulants (Vitamin K dependent) [2]. Their deficiency leads to an inability to inactivate Factors Va and VIIIa, resulting in a hypercoagulable state. **Clinical Pearls for NEET-PG:** * **Most common inherited thrombophilia:** Factor V Leiden [1]. * **Most common acquired thrombophilia:** Antiphospholipid Antibody Syndrome (APS) [1]. * **Warfarin-induced skin necrosis:** Classically seen in patients with **Protein C deficiency** when starting Warfarin without heparin bridging. * **Mixing Study:** Used to differentiate LA from factor deficiencies; LA will **not** correct upon mixing with normal plasma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 133-135. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 624-625.

Q: Two siblings have osteogenesis imperfecta, but their parents are normal. What is the mechanism of inheritance?

Germline mosaicism. **Explanation:** The correct answer is **Germline Mosaicism** (also known as Gonadal Mosaicism). **Why it is correct:** In this scenario, the parents are phenotypically normal (they do not carry the mutation in their somatic cells), yet they have **two** children with an autosomal dominant condition (Osteogenesis Imperfecta). If it were a simple "new mutation," it would be highly improbable for it to occur twice in the same family. Germline mosaicism occurs when a mutation happens post-zygotically during the parent's embryonic development, affecting only a subset of germ cells (sperm or eggs) but not the somatic cells [1]. Thus, the parent is healthy but can pass the mutation to multiple offspring. **Why other options are incorrect:** * **Anticipation:** Refers to the increasing severity or earlier onset of a disease in successive generations, typically seen in trinucleotide repeat disorders (e.g., Huntington’s, Fragile X). * **Genomic Imprinting:** Involves differential expression of a gene depending on whether it is inherited from the mother or father (e.g., Prader-Willi and Angelman syndromes). * **New Mutation (De novo):** While Osteogenesis Imperfecta often results from new mutations, a single new mutation cannot explain why **two** siblings are affected if the parents are normal. **NEET-PG High-Yield Pearls:** * **Classic Example:** Germline mosaicism is the most common explanation when healthy parents have multiple children with **Osteogenesis Imperfecta** or **Duchenne Muscular Dystrophy (DMD)**. * **Recurrence Risk:** In germline mosaicism, the recurrence risk for siblings is significantly higher than the general population risk, despite normal parental testing. * **Definition:** Presence of two or more genetically different cell lines in the gonads [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 170-171.

Question 1

What is the Leiden factor?

Accepted Answer

Factor V

Answer

Factor VI

Answer

Factor VIII

Answer

Factor IV

Question 2

Keratinizing metaplasia of salivary glands results due to the deficiency of which vitamin?

Accepted Answer

Vitamin A

Answer

Thiamine

Answer

Riboflavin

Answer

Vitamin E

Question 3

In malignant hypertension, necrosis is of which type?

Accepted Answer

Fibrinoid necrosis

Answer

Caseous necrosis

Answer

Liquifactive necrosis

Answer

Coagulative necrosis

Question 4

NSAID drug-induced edema is primarily due to which of the following mechanisms?

Accepted Answer

Increased hydrostatic pressure

Answer

Protein-losing enteropathy

Answer

Endothelial damage due to IL-2

Answer

Low oncotic pressure

Question 5

Which of the following is not an example of apoptosis?

Accepted Answer

Tumor necrosis

Answer

Graft versus host disease

Answer

Menstrual cycle

Answer

Pathological atrophy following duct obstruction

Question 6

Which of the following pigments is NOT derived from hemoglobin?

Accepted Answer

Lipofuscin

Answer

Hematin

Answer

Hemosiderin

Answer

Bilirubin

Question 7

Which stain is used to identify Gaucher cells?

Accepted Answer

Periodic Acid Schiff (PAS)

Answer

Von Kossa stain

Answer

Oil red O

Answer

Sudan Black B

Question 8

All of the following are true of red infarction, except?

Accepted Answer

Occurs in end arterial occlusion

Answer

Occurs with venous occlusion

Answer

Seen in loose tissues

Answer

Occurs in previously congested tissue

Question 9

Which of the following is NOT an inherited coagulation disorder?

Accepted Answer

Lupus anticoagulant

Answer

Protein C deficiency

Answer

Protein S deficiency

Answer

Factor V Leiden mutation

Question 10

Two siblings have osteogenesis imperfecta, but their parents are normal. What is the mechanism of inheritance?

Accepted Answer

Germline mosaicism

Answer

Anticipation

Answer

Genomic imprinting

Answer

New mutation

General Pathology — MCQs

General Pathology — MCQs

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