General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 771: CD95 is a marker of which of the following?

A. Intrinsic pathway of apoptosis
B. Extrinsic pathway of apoptosis (Correct Answer)
C. Monocyte
D. Leucocyte

Explanation: **Explanation:** **CD95**, also known as the **Fas receptor**, is a critical death receptor located on the cell surface. It belongs to the Tumor Necrosis Factor (TNF) receptor family and plays a central role in the **Extrinsic (Death Receptor-Initiated) Pathway of Apoptosis** [1]. 1. **Why Option B is Correct:** The extrinsic pathway is triggered when specific ligands (like FasL) bind to death receptors on the plasma membrane [1]. When FasL (CD95L) binds to CD95, it leads to the trimerization of the receptor and the recruitment of the adapter protein **FADD** (Fas-associated death domain) [1]. This complex activates **Caspase-8** (the initiator caspase of this pathway), which subsequently activates executioner caspases, leading to cell death [1]. 2. **Why Other Options are Incorrect:** * **Option A:** The **Intrinsic pathway** (Mitochondrial pathway) is triggered by internal cellular stress (DNA damage, withdrawal of growth factors) [1]. It is regulated by the Bcl-2 family of proteins and involves the release of **Cytochrome c** and the activation of **Caspase-9**, not CD95 [1]. * **Option C & D:** While CD95 can be expressed on various cells, including activated lymphocytes, it is not used as a diagnostic lineage marker for monocytes or general leukocytes. Markers like CD14 (monocytes) or CD45 (leukocytes) are used for that purpose. **High-Yield Clinical Pearls for NEET-PG:** * **ALPS (Autoimmune Lymphoproliferative Syndrome):** Caused by mutations in the Fas receptor (CD95), Fas ligand, or Caspase-8/10, leading to a failure of lymphocyte apoptosis. * **FLIP:** A protein used by some viruses and cancer cells to inhibit the extrinsic pathway by binding to pro-caspase-8 [2]. * **Initiator Caspases:** Extrinsic = Caspase 8 & 10; Intrinsic = Caspase 9 [1]. * **Executioner Caspases:** Caspase 3, 6, and 7 (common to both pathways). **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, pp. 64-67. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310.

Question 772: Which stain is used for melanin?

A. Masson Fontana (Correct Answer)
B. Prussian blue
C. Masson trichrome
D. Congo red

Explanation: **Explanation:** **Masson Fontana (Option A)** is the correct answer. It is an **argentaffin stain**, meaning melanin has the inherent ability to reduce silver nitrate to metallic silver without the need for an external reducing agent. This results in melanin granules appearing black against a pink/red background. It is the gold standard histochemical stain for identifying melanin in conditions like malignant melanoma or to distinguish it from other brown pigments. **Analysis of Incorrect Options:** * **Prussian Blue (Option B):** This is used to detect **Ferric iron (Hemosiderin)**. It is a classic stain used in cases of hemochromatosis or to identify "heart failure cells" (siderophages) in the lungs. * **Masson Trichrome (Option C):** This is a connective tissue stain used to differentiate **collagen (blue/green)** from smooth muscle and epithelium (red). It is frequently used to assess the degree of fibrosis in liver cirrhosis or chronic kidney disease. * **Congo Red (Option D):** This is the specific stain for **Amyloid** [1]. Under polarized light, amyloid stained with Congo red exhibits a characteristic **apple-green birefringence** [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Melanin Bleaching:** If a lesion is heavily pigmented, "bleaching" with hydrogen peroxide or potassium permanganate is done to see nuclear details. * **DOPA Reaction:** This is an enzyme histochemical method used to identify melanocytes by detecting tyrosinase activity. * **IHC Markers:** For malignant melanoma, **S-100** (sensitive), **HMB-45** (specific), and **Melan-A** are the high-yield immunohistochemical markers. * **Other Silver Stains:** Do not confuse Masson Fontana with **Von Kossa** (used for Calcium) or **Reticulin stain** (used for Type III Collagen). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Question 773: What is the most common cause of death in primary amyloidosis?

A. Respiratory failure
B. Renal failure
C. Cardiac failure (Correct Answer)
D. Septicemia

Explanation: **Explanation:** **Primary Amyloidosis (AL Amyloidosis)** is characterized by the deposition of monoclonal immunoglobulin light chains (secreted by plasma cell dyscrasias) into various tissues [1]. **Why Cardiac Failure is the Correct Answer:** The heart is the most critical organ involved in AL amyloidosis, affected in approximately 50-60% of cases. The amyloid fibrils deposit in the myocardium, leading to **Restrictive Cardiomyopathy** [2]. This results in diastolic dysfunction, thickening of the ventricular walls, and conduction disturbances [2]. **Cardiac failure (congestive heart failure) and fatal arrhythmias** are the leading causes of mortality, accounting for nearly 40-50% of deaths in these patients. **Analysis of Incorrect Options:** * **Renal Failure (B):** While the kidney is the most frequently involved organ in both primary (AL) and secondary (AA) amyloidosis (often presenting as Nephrotic Syndrome), it is the second most common cause of death. In secondary (AA) amyloidosis, renal failure is a more prominent cause of mortality than in AL amyloidosis. * **Respiratory Failure (A):** Though amyloid can deposit in the alveolar septa or tracheobronchial tree, it rarely leads to isolated respiratory failure as the primary cause of death. * **Septicemia (D):** While patients may be immunocompromised due to underlying plasma cell dyscrasias or chemotherapy, sepsis is a complication rather than the characteristic primary cause of death associated with the amyloid deposition itself. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organ involved:** Kidney (presents as proteinuria/nephrotic syndrome). * **Most common cause of death:** Cardiac failure (Restrictive Cardiomyopathy). * **Diagnostic Gold Standard:** Tissue biopsy showing **Apple-green birefringence** under polarized light with Congo Red stain [3]. * **Cardiac Biomarkers:** NT-proBNP and Troponin are the best prognostic indicators in AL amyloidosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 266-267. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, pp. 580-581. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Question 774: Deficiency of which enzyme causes Tay-Sachs disease?

A. Hexosaminidase A (Correct Answer)
B. Alpha-L-iduronidase
C. Alpha-galactosidase A
D. Acid alpha-glucosidase

Explanation: **Explanation:** **Tay-Sachs Disease** is an autosomal recessive lysosomal storage disorder belonging to the group of **GM2 gangliosidoses**. It is caused by a deficiency of the enzyme **Hexosaminidase A**, which leads to the toxic accumulation of GM2 gangliosides, primarily within the neurons of the central nervous system. * **Why Option A is correct:** Hexosaminidase A (composed of $\alpha$ and $\beta$ subunits) requires an activator protein to degrade GM2 ganglioside. A mutation in the *HEXA* gene on chromosome 15 leads to enzyme deficiency, resulting in progressive neurodegeneration and the characteristic "cherry-red spot" on the macula [1]. * **Why incorrect options are wrong:** * **B. Alpha-L-iduronidase:** Deficiency causes **Hurler Syndrome** (Mucopolysaccharidosis I) [2], characterized by corneal clouding and hepatosplenomegaly. * **C. Alpha-galactosidase A:** Deficiency causes **Fabry Disease**, an X-linked disorder presenting with angiokeratomas, peripheral neuropathy, and renal failure. * **D. Acid alpha-glucosidase (Acid Maltase):** Deficiency causes **Pompe Disease** (Glycogen Storage Disease Type II), leading to massive cardiomegaly and muscular hypotonia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Morphology:** Histology shows "onion-skin" appearance of lysosomes (whorled configurations) [1]. 2. **Clinical Triad:** Progressive neurodegeneration, developmental delay, and **Cherry-red spot** on the macula [1]. 3. **Key Distinction:** Unlike Gaucher or Niemann-Pick disease, Tay-Sachs has **NO hepatosplenomegaly**. 4. **Epidemiology:** High prevalence in the Ashkenazi Jewish population. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 161. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 163-164.

Question 775: Which of the following conditions does not typically progress to carcinoma?

A. Bowen's disease
B. Bowenoid papulosis (Correct Answer)
C. Leukoplakia
D. Erythroplakia

Explanation: **Explanation:** The correct answer is **Bowenoid papulosis**. While it is histologically indistinguishable from Bowen’s disease (showing full-thickness squamous dysplasia/carcinoma in situ), it follows a **benign clinical course**. It typically presents as multiple reddish-brown pigmented papules on the genitalia of young, sexually active adults. Unlike Bowen’s disease, it rarely progresses to invasive squamous cell carcinoma and often regresses spontaneously. **Analysis of Incorrect Options:** * **Bowen’s Disease:** This is a form of squamous cell carcinoma in situ (CIS) involving the skin or mucosal surfaces [1]. It presents as a slow-growing, erythematous plaque and has a definite risk of progressing to invasive squamous cell carcinoma (approx. 3-5%). * **Leukoplakia:** Defined as a clinical white patch that cannot be scraped off [2]. It is a well-known premalignant lesion of the oral cavity, with a transformation rate to malignancy ranging from 1% to 20%. * **Erythroplakia:** This presents as a red, velvety, circumscribed area. It is significantly more worrisome than leukoplakia, as over 50% of cases show invasive carcinoma or severe dysplasia at the time of biopsy. **NEET-PG High-Yield Pearls:** * **HPV Association:** Both Bowen’s disease and Bowenoid papulosis are strongly associated with **HPV type 16**. * **The "Rule of Red":** In oral pathology, red lesions (Erythroplakia) carry a much higher risk of malignancy than white lesions (Leukoplakia). * **Clinical Distinction:** Always differentiate by age and behavior—Bowenoid papulosis occurs in younger patients and is clinically benign; Bowen’s disease occurs in older patients and is a true precursor to malignancy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1002-1004. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1000-1002.

Question 776: Which stain is characteristically used for the diagnosis of amyloidosis?

A. Congo red (Correct Answer)
B. Thioflavin T
C. Reticulin stain
D. Gram's iodine

Explanation: **Explanation:** **Congo Red** is the gold standard and most characteristic stain for diagnosing amyloidosis [1]. Amyloid is a pathologic proteinaceous substance deposited in the extracellular space. When stained with Congo Red and viewed under **polarized light**, it exhibits a pathognomonic **apple-green birefringence** [1]. This occurs because the dye molecules align parallel to the highly organized cross-beta-pleated sheet structure of the amyloid fibrils [1]. **Analysis of Options:** * **B. Thioflavin T:** While this fluorescent dye binds to amyloid and is highly sensitive, it is **not specific**. It is often used for screening in research settings but is not the "characteristic" diagnostic stain used in routine clinical pathology compared to Congo Red. * **C. Reticulin stain:** This is a silver-based stain used to visualize Type III collagen fibers (reticulin). It is used to evaluate liver architecture or bone marrow fibrosis, not amyloid. * **D. Gram’s iodine:** Historically, Virchow used iodine to identify amyloid (hence the name "amyloid" or starch-like), which turns the deposits mahogany brown. However, this is a gross macroscopic test and is no longer used for definitive microscopic diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **H&E Appearance:** Amyloid appears as an extracellular, amorphous, eosinophilic (pink) hyaline material [1]. * **Most Common Type:** Systemic AL (Light chain) amyloidosis is associated with plasma cell dyscrasias [1]. * **Biopsy Site:** The most common site for screening systemic amyloidosis is **Abdominal Fat Pad aspiration** or Rectal biopsy. * **Secondary Amyloidosis (AA):** Associated with chronic inflammation (e.g., TB, Rheumatoid Arthritis). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Question 777: Fibrin is degraded by which of the following?

A. Plasminogen
B. Thromboplastin
C. Plasmin (Correct Answer)
D. Fibrin degradation products

Explanation: ### Explanation **Correct Answer: C. Plasmin** **Mechanism:** The process of breaking down a fibrin clot is known as **fibrinolysis**. The central mediator of this process is **Plasmin**, a potent serine protease [1]. Plasmin is generated from its inactive precursor, plasminogen, by activators such as Tissue Plasminogen Activator (tPA) or Urokinase [1]. Once activated, plasmin cleaves the fibrin meshwork at specific sites, breaking the polymer into soluble fragments known as Fibrin Degradation Products (FDPs), including D-dimers. **Analysis of Incorrect Options:** * **A. Plasminogen:** This is the inactive zymogen (precursor) of plasmin [1]. It has no enzymatic activity on fibrin until it is converted into plasmin. * **B. Thromboplastin (Tissue Factor):** This is a trigger for the **extrinsic pathway** of the coagulation cascade. Its role is to promote clot formation (pro-coagulant) by activating Factor VII, not to degrade fibrin. * **D. Fibrin Degradation Products (FDPs):** These are the *end-products* of fibrinolysis. While they have weak anticoagulant properties, they do not actively degrade the fibrin clot; they are the result of the degradation. **High-Yield Clinical Pearls for NEET-PG:** * **D-Dimer:** A specific FDP produced only when *cross-linked* fibrin is degraded. It is a highly sensitive (but non-specific) marker used to rule out Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). * **Alpha-2 Antiplasmin:** The primary physiological inhibitor of plasmin, ensuring fibrinolysis remains localized [1]. * **Therapeutic Application:** Recombinant tPA (Alteplase) is used clinically as a "clot buster" in acute MI and ischemic stroke to catalyze the production of plasmin [1]. * **Inhibitors:** Tranexamic acid inhibits fibrinolysis by preventing the binding of plasminogen to fibrin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 130-132.

Question 778: Which of the following is a pathological calcification?

A. Suprasellar calcification (Correct Answer)
B. Basal ganglia calcification
C. Pineal body calcification
D. Choroid calcification

Explanation: Pathological calcification is the abnormal deposition of calcium salts in tissues [1]. It is broadly categorized into **Dystrophic calcification** (occurs in dead/dying tissues with normal serum calcium) and **Metastatic calcification** (occurs in normal tissues due to hypercalcemia) [1,2]. **Why Suprasellar Calcification is the Correct Answer:** Suprasellar calcification is a classic radiological hallmark of a **Craniopharyngioma** (specifically the adamantinomatous type). In this condition, calcification occurs within the necrotic debris and "wet keratin" of the tumor. Since this deposition occurs within neoplastic/diseased tissue, it is a form of **Dystrophic Calcification**, making it a pathological process [3]. **Analysis of Incorrect Options:** * **B, C, and D (Basal Ganglia, Pineal Body, and Choroid Plexus):** These are considered **Physiological Calcifications**. They occur as a result of aging or normal metabolic processes without underlying tissue necrosis or systemic calcium imbalance. * **Pineal gland calcification** is common after puberty and serves as a useful midline marker on X-rays. * **Choroid plexus calcification** is a frequent incidental finding in elderly patients. * **Basal ganglia calcification** can be physiological in the elderly (incidental), though it can be pathological in specific conditions like Fahr’s syndrome or hypoparathyroidism. However, in a general comparative context, suprasellar calcification is always pathological. **NEET-PG High-Yield Pearls:** * **Craniopharyngioma:** Derived from Rathke’s pouch; suprasellar calcification is seen in ~90% of pediatric cases. * **Psammoma Bodies:** A form of dystrophic calcification seen in Papillary thyroid carcinoma, Meningioma, and Serous cystadenocarcinoma of the ovary [1]. * **Monckeberg’s Arteriosclerosis:** Dystrophic calcification of the tunica media of medium-sized arteries; does not obstruct the lumen. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 134-135. [2] 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, pp. 76-77. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 655-656.

Question 779: In an Autosomal Recessive (AR) disorder, if one parent is normal and the other is a carrier, and the child is affected, what is the most likely explanation for this inheritance pattern?

A. Germline mosaicism
B. Genomic imprinting
C. Mitochondrial inheritance
D. Uniparental disomy (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Uniparental Disomy (UPD)** **Why it is correct:** In classic Autosomal Recessive (AR) inheritance, an affected child must inherit one mutant allele from *each* parent (both parents must be carriers or affected) [1]. In this scenario, one parent is "normal" (homozygous wild-type). For the child to be affected, they must have received two copies of the mutant allele from the carrier parent and zero copies from the normal parent. This phenomenon is called **Uniparental Disomy (UPD)**. Specifically, if the child inherits two identical copies of the mutant chromosome from the carrier parent, it is termed **isodisomy**, leading to the expression of an AR disorder despite only one parent being a carrier. **Why other options are incorrect:** * **A. Germline mosaicism:** This occurs when a mutation happens in a subset of gametes. It typically explains how two healthy parents have multiple children with an **Autosomal Dominant** condition (e.g., Osteogenesis Imperfecta). * **B. Genomic imprinting:** This refers to the epigenetic silencing of one parental allele. While UPD can lead to imprinting disorders (like Prader-Willi or Angelman syndromes), imprinting itself does not explain the inheritance of a classic AR disease from a single carrier. * **C. Mitochondrial inheritance:** This follows a maternal pattern where all children of an affected mother are affected, but children of an affected father are not. It does not follow AR rules. **High-Yield Clinical Pearls for NEET-PG:** * **Prader-Willi Syndrome:** Most common cause is a deletion on paternal Ch 15, but 25% of cases are due to **Maternal UPD**. * **Angelman Syndrome:** Most common cause is a deletion on maternal Ch 15, but 5% of cases are due to **Paternal UPD**. * **Cystic Fibrosis:** Suspect UPD if a child has CF but only one parent is a carrier. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 53-54.

Question 780: Paternal 15 chromosome deletion is seen in which of the following conditions?

A. Angelman syndrome
B. Prader Willi syndrome (Correct Answer)
C. Down syndrome
D. Turner syndrome

Explanation: This question tests the concept of **Genomic Imprinting**, an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner [1]. ### **Explanation of the Correct Answer** **Prader-Willi Syndrome (PWS)** occurs due to the loss of function of genes in the **15q11-q13** region on the **paternal chromosome** [1]. In normal individuals, the maternal copy of these specific genes is silenced (imprinted), so the individual relies solely on the paternal copy. If the paternal segment is deleted (70% of cases) or if there is Maternal Uniparental Disomy (25%), no functional genes remain, leading to the syndrome. * **Clinical Presentation:** Neonatal hypotonia, hyperphagia leading to morbid obesity, hypogonadism, and small hands/feet. ### **Analysis of Incorrect Options** * **A. Angelman Syndrome:** This is the "sister" condition to PWS. It involves a deletion of the same region (15q11-q13) but on the **maternal chromosome** [1]. It results in the "Happy Puppet" profile: inappropriate laughter, ataxia, and seizures [1]. * **C. Down Syndrome:** Caused by **Trisomy 21**. It is a numerical chromosomal aberration, not related to imprinting or chromosome 15. * **D. Turner Syndrome:** Caused by **Monosomy X (45, XO)**. It is characterized by short stature, webbed neck, and streak ovaries. ### **High-Yield Clinical Pearls for NEET-PG** * **Mnemonic:** **P**ader-Willi = **P**aternal deletion; **A**ngelman = **M**aternal deletion (**MAP**: Maternal Angelman Prader). * **Uniparental Disomy (UPD):** PWS can also be caused by inheriting two copies of chromosome 15 from the mother (Maternal UPD) and none from the father. * **Diagnosis:** The gold standard screening test for both syndromes is **DNA Methylation Analysis** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 181-183.

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