General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 911: What is true about dystrophic calcification?

A. This is the most frequent type of pathologic calcification.
B. In the mouth, areas of dystrophic calcification may frequently be found in the gingiva, tongue, or cheek.
C. One of the most common intraoral dystrophic calcifications is found in the pulp of teeth.
D. All of the above. (Correct Answer)

Explanation: **Explanation:** **Dystrophic calcification** is the deposition of calcium salts in **dead or dying tissues** despite **normal serum calcium levels** and normal calcium metabolism [1]. It is a hallmark of cellular injury. 1. **Why Option A is correct:** Dystrophic calcification is indeed the **most frequent type** of pathologic calcification [1]. It occurs in areas of necrosis (coagulative, liquefactive, or caseous) and in damaged tissues such as atherosclerotic plaques or aging heart valves. 2. **Why Option B is correct:** In the oral cavity, chronic inflammation or minor trauma to soft tissues (gingiva, tongue, or cheek) can lead to localized tissue death, subsequently resulting in dystrophic calcification (e.g., calcinosis cutis or idiopathic soft tissue calcification) [2]. 3. **Why Option C is correct:** **Pulp stones (denticles)** or diffuse calcifications in the dental pulp are classic examples of dystrophic calcification. They often occur due to chronic pulpitis, trauma, or age-related degenerative changes in the pulp tissue. Since all statements accurately describe the nature and clinical presentation of dystrophic calcification, **Option D** is the correct answer. --- ### **High-Yield NEET-PG Pearls:** * **Mechanism:** Initiated by membrane damage; calcium binds to phospholipids in membrane vesicles, forming crystalline calcium phosphate. * **Morphology:** Macroscopically appears as fine, white granules or clumps (gritty feel). Microscopically, it shows basophilic (blue-purple) deposits. * **Psammoma Bodies:** These are laminated, concentric calcified structures found in specific tumors (e.g., **P**apillary thyroid carcinoma, **S**erous cystadenocarcinoma of ovary, **M**eningioma, **M**esothelioma) [1]. * **Dystrophic vs. Metastatic:** * **Dystrophic:** Normal serum Ca²⁺ + Damaged tissue [1]. * **Metastatic:** High serum Ca²⁺ + Normal tissue (usually affects lungs, kidneys, and gastric mucosa due to alkaline pH) [1], [3]. **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] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 655-656. [3] 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.

Question 912: Mallory bodies are composed of:

A. Fat droplets
B. Mitochondria
C. Lysosomal enzymes
D. Intermediate filaments (Correct Answer)

Explanation: **Explanation:** Mallory bodies (also known as Mallory-Denk bodies) are characteristic eosinophilic intracytoplasmic inclusions found in hepatocytes. They are primarily composed of **intermediate filaments**, specifically **pre-keratin (Cytokeratin 8 and 18)**, which have become ubiquitinated and aggregated due to cellular stress and protein misfolding. **Why the other options are incorrect:** * **A. Fat droplets:** These are seen in steatosis (fatty change). While often co-occurring with Mallory bodies in alcoholic liver disease, they are distinct clear vacuoles, not eosinophilic inclusions [1]. * **B. Mitochondria:** Mitochondrial swelling (megamitochondria) can occur in liver injury, but they do not form the rope-like eosinophilic aggregates characteristic of Mallory bodies. * **C. Lysosomal enzymes:** These are involved in autophagy and cellular digestion. While lysosomes may attempt to degrade Mallory bodies, they are not a structural component of the bodies themselves. **High-Yield NEET-PG Pearls:** * **Appearance:** They appear as "twisted-rope" or "irregularly shaped" eosinophilic (pink) masses in the perinuclear region of hepatocytes [1]. * **Classic Association:** Most commonly associated with **Alcoholic Hepatitis** [1]. * **Other Associations (Mnemonic: "NAAL"):** **N**on-alcoholic steatohepatitis (NASH), **A**lcoholic hepatitis, **A**lpha-1 antitrypsin deficiency, **L**iver cirrhosis (Primary Biliary Cholangitis) and Wilson disease [1]. * **Staining:** They stain positive with **Ubiquitin** and **p62** antibodies. * **Cellular Mechanism:** They represent a failure of the proteasome-mediated degradation of damaged cytoskeletal proteins. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 388-389.

Question 913: Aspiration of fluid around the knee joint of a diabetic patient undergoing dialysis would show which of the following?

A. Beta-2 microglobulin (Correct Answer)
B. AA amyloid
C. AL amyloid
D. Lactoferrin

Explanation: **Explanation:** The correct answer is **Beta-2 microglobulin (A)**. This case describes **Dialysis-Related Amyloidosis (DRA)**, a well-recognized complication in patients undergoing long-term hemodialysis [1]. **Why Beta-2 Microglobulin is correct:** Beta-2 microglobulin ($\beta_2$M) is a component of the MHC Class I molecule found on all nucleated cells [1]. In healthy individuals, it is filtered by the kidneys. However, in patients with end-stage renal disease (ESRD), $\beta_2$M levels rise significantly because standard dialysis membranes cannot efficiently remove it. Over time, these proteins undergo conformational changes and deposit as amyloid fibrils, particularly in **osteoarticular structures** like the synovium of the knee, hip, and the transverse carpal ligament (leading to Carpal Tunnel Syndrome) [1]. **Why other options are incorrect:** * **AA Amyloid (B):** Derived from Serum Amyloid-Associated (SAA) protein, an acute-phase reactant. It is seen in **Secondary Amyloidosis** associated with chronic inflammatory conditions like Rheumatoid Arthritis, TB, or Osteomyelitis. * **AL Amyloid (C):** Derived from immunoglobulin light chains [2]. It is seen in **Primary Amyloidosis**, typically associated with Plasma Cell Dyscrasias like Multiple Myeloma [2]. * **Lactoferrin (D):** An iron-binding protein found in neutrophil granules. While present in inflammatory joint fluid (like septic arthritis), it is not a precursor for amyloid fibrils in dialysis patients. **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** Like all amyloids, $\beta_2$M shows **Apple-green birefringence** under polarized light with Congo Red stain [3]. This reaction is caused by the crossed ̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̢̡̡ ̡̡̡̡̡ ̢̡-pleated configuration of amyloid fibrils [3]. * **Classic Presentation:** A long-term dialysis patient presenting with bilateral Carpal Tunnel Syndrome or persistent joint effusions. * **Scapulohumeral Periarthritis:** Another common site for $\beta_2$M deposition. * **Diagnosis:** Definitive diagnosis is made via biopsy of the synovium or bone showing amyloid deposits. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 266. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 266-267. [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 914: Absence of rete pegs is seen in which of the following conditions?

A. Oral submucous fibrosis (OSMF) (Correct Answer)
B. Lichen planus
C. Leukoplakia
D. All of the above

Explanation: **Explanation:** The correct answer is **Oral submucous fibrosis (OSMF)**. **1. Why OSMF is correct:** Oral submucous fibrosis is a chronic, progressive, and potentially malignant condition characterized by juxta-epithelial inflammatory reaction followed by progressive **fibrosis of the lamina propria**. As the subepithelial connective tissue becomes densely hyalinized and fibrotic, it exerts a "flattening" effect on the overlying epithelium. This leads to the **atrophy of the epithelium** and the characteristic **loss or absence of rete pegs** (the epithelial extensions that normally project into the underlying connective tissue). **2. Why other options are incorrect:** * **Lichen Planus:** This condition is characterized by a "saw-tooth" appearance of rete pegs due to liquefactive degeneration of the basal cell layer. The rete pegs are altered in shape but are classically present and pointed, not absent. * **Leukoplakia:** This is a clinical term for a white patch [1], [2]. Histologically, it often shows hyperkeratosis and acanthosis (thickening of the epithelium). In many cases, the rete pegs become elongated or "drop-shaped" (especially in dysplastic leukoplakia), rather than absent [1]. **3. NEET-PG High-Yield Pearls for OSMF:** * **Etiology:** Strongly associated with **Areca nut (betel nut)** chewing [1]. * **Clinical Hallmark:** Progressive inability to open the mouth (**Trismus**) due to vertical fibrous bands in the buccal mucosa. * **Histopathology:** Hyalinization of collagen, decreased vascularity, and epithelial atrophy with a high risk of transformation to **Squamous Cell Carcinoma** (3–7% risk) [1]. * **Key Histological Feature:** Flattening of the dermo-epidermal junction (Loss of rete pegs). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 344-345. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, p. 1000.

Question 915: Which of the following cytokines does not play a role in the production, maintenance, or activation of lymphocytes?

A. IL-1
B. IL-2
C. IL-4
D. IL-12 (Correct Answer)

Explanation: **Explanation:** The correct answer is **IL-12**. While IL-12 is a critical cytokine in the immune response, its primary role is the **differentiation** of naive T-cells into Th1 cells [1] and the activation of Natural Killer (NK) cells. It is produced by antigen-presenting cells (macrophages and dendritic cells) rather than being a primary driver for the production or maintenance of the lymphocyte pool itself. **Analysis of Options:** * **IL-1 (Incorrect):** Produced by macrophages, IL-1 acts as a costimulator for **T-cell activation** and promotes the proliferation of B-cells. It is essential for the early stages of lymphocyte response. * **IL-2 (Incorrect):** Known as the **"T-cell growth factor,"** it is the most critical cytokine for the proliferation (production/maintenance) of T-lymphocytes [1]. It acts in an autocrine fashion to drive clonal expansion [1]. * **IL-4 (Incorrect):** Produced by Th2 cells, it is vital for **B-cell activation**, proliferation, and isotype switching to IgE. It also promotes the differentiation of naive T-cells into Th2 cells. **High-Yield NEET-PG Pearls:** * **IL-2** is the target of immunosuppressants like Cyclosporine and Tacrolimus (which inhibit IL-2 production via calcineurin inhibition). * **IL-7** (not listed) is the primary cytokine responsible for the **maintenance** of memory T-cells and early lymphoid progenitors in the bone marrow. * **IL-12 deficiency** leads to disseminated mycobacterial infections due to the inability to mount a Th1/IFN-$\gamma$ response. * **IL-1, IL-6, and TNF-$\alpha$** are the "pro-inflammatory triad" responsible for the acute phase response and fever. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 206-218.

Question 916: Venous emboli are most often lodged in which organ?

A. Intestines
B. Lungs (Correct Answer)
C. Kidneys
D. Heart

Explanation: **Explanation:** **Correct Option: B. Lungs** The primary destination for venous emboli is the lungs [1]. This is due to the anatomical pathway of the venous circulation. Most venous emboli originate from **Deep Vein Thrombosis (DVT)** in the lower extremities [4]. These thrombi travel through progressively larger vessels (popliteal → femoral → iliac veins) into the **Inferior Vena Cava (IVC)**, then into the right atrium and right ventricle of the heart. From the right ventricle, they are ejected into the **pulmonary arteries** [3]. Because the pulmonary arterial tree tapers into a vast network of fine capillaries, the emboli become "sieved" and lodged there, leading to **Pulmonary Embolism (PE)** [2]. **Why other options are incorrect:** * **A & C (Intestines and Kidneys):** These organs are common sites for **systemic (arterial) emboli** [3]. Arterial emboli usually originate from the left heart (e.g., atrial fibrillation or mural thrombi) and travel through the aorta to reach systemic organs. Venous emboli cannot reach these organs unless they bypass the lungs via a right-to-left shunt (Paradoxical Embolism) [2]. * **D (Heart):** While the heart is a common *source* of emboli (left heart for systemic, right heart for pulmonary), it is not a common site for venous emboli to lodge, as they simply pass through the right-sided chambers. **High-Yield Clinical Pearls for NEET-PG:** * **Most common source:** >95% of pulmonary thromboemboli originate from deep veins of the leg above the knee [4]. * **Paradoxical Embolism:** A venous embolus that enters systemic circulation (e.g., brain, kidneys) via an **Atrial Septal Defect (ASD)** or Patent Foramen Ovale [2][3]. * **Saddle Embolus:** A large embolus that lodges at the bifurcation of the main pulmonary artery, often causing sudden death. * **Dual Blood Supply:** The lungs have a dual supply (Pulmonary and Bronchial arteries), which is why most small pulmonary emboli do not result in infarction [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 705. [2] 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. 144-145. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 137-138. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 323-324.

Question 917: Transfusion of stored blood causes which of the following?

A. Hyperkalemia (Correct Answer)
B. Hyponatremia
C. Hypercalcemia
D. Hypokalemia

Explanation: ### Explanation **Correct Option: A. Hyperkalemia** The primary reason for hyperkalemia in stored blood is the **failure of the Na⁺/K⁺-ATPase pump**. During storage at 1–6°C, the metabolic activity of Red Blood Cells (RBCs) slows down, leading to ATP depletion. Without ATP, the Na⁺/K⁺-ATPase pump cannot maintain the concentration gradient, causing potassium to leak out of the RBCs into the plasma. This phenomenon is known as the **"Storage Lesion."** The concentration of extracellular potassium increases linearly with the duration of storage, potentially reaching levels as high as 30 mmol/L by the end of the shelf life. **Analysis of Incorrect Options:** * **B. Hyponatremia:** While sodium levels may slightly decrease as sodium moves into the RBCs (the reverse of potassium leakage), clinically significant hyponatremia is not a classic complication of transfusion. * **C. Hypercalcemia:** Transfusion actually causes **Hypocalcemia**. Citrate, used as an anticoagulant in blood bags, chelates (binds) free ionized calcium in the recipient's blood. * **D. Hypokalemia:** While hypokalemia can occasionally occur *after* transfusion (as viable RBCs begin to take up potassium again once warmed in the body), the immediate effect of transfusing the stored unit itself is an infusion of high-potassium plasma. **High-Yield Clinical Pearls for NEET-PG:** * **Citrate Toxicity:** Rapid transfusion of multiple units can lead to hypocalcemia and hypomagnesemia due to citrate binding. * **2,3-DPG Levels:** Stored blood shows a **decrease in 2,3-Diphosphoglycerate (2,3-DPG)**, which shifts the oxygen dissociation curve to the **left**, meaning hemoglobin holds onto oxygen more tightly (decreased O₂ delivery to tissues). * **Acidosis:** Stored blood becomes progressively **acidic** due to the accumulation of lactate and pyruvic acid from anaerobic glycolysis. * **Pediatric Alert:** Fresh blood (<7 days old) is preferred for neonatal exchange transfusions to avoid the risks of hyperkalemia and low 2,3-DPG.

Question 918: CD-95 is a marker of?

A. Death receptor (Correct Answer)
B. Tumor cells in T-ALL
C. Monocytes
D. NK cells

Explanation: **Explanation:** **CD95**, also known as **Fas receptor**, is a critical cell surface marker that belongs to the Tumor Necrosis Factor Receptor (TNFR) superfamily [1]. It plays a central role in the **extrinsic pathway of apoptosis** [1]. 1. **Why Option A is correct:** CD95 is termed a **Death Receptor** because it contains a cytoplasmic "death domain." [1] When CD95 binds to its ligand (**FasL/CD178**), it triggers the recruitment of FADD (Fas-associated death domain) and pro-caspase 8, forming the **DISC** (Death-Inducing Signaling Complex) [1], [3]. This leads to the activation of Caspase 8, ultimately resulting in programmed cell death. 2. **Why other options are incorrect:** * **Option B (T-ALL):** While CD95 can be expressed on various lymphocytes, the characteristic markers for T-ALL are T-cell antigens like **CD3, CD7, and CD1a**. * **Option C (Monocytes):** The classic markers for monocytes are **CD14** and CD16. * **Option D (NK cells):** The definitive markers for NK cells are **CD56** and **CD16**. **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. It results in a failure of self-reactive T-cells to undergo apoptosis, leading to lymphadenopathy, splenomegaly, and autoimmunity. * **Caspase 8** is the initiator caspase for the extrinsic pathway [1], [2], while **Caspase 9** is for the intrinsic (mitochondrial) pathway [2]. * **Caspase 3 and 6** are the common executioner caspases. **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. 67. [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. 64-65. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310.

Question 919: Which of the following statements regarding reversible cell injury is FALSE?

A. Formation of amorphous densities in the mitochondrial matrix (Correct Answer)
B. Diminished generation of adenosine triphosphate (ATP)
C. Formation of blebs in the plasma membrane
D. Detachment of ribosomes from the granular endoplasmic reticulum

Explanation: ### Explanation The hallmark of **reversible cell injury** is the cell's ability to return to homeostasis if the stimulus is removed [1]. The transition to **irreversible injury** (cell death) is characterized by two phenomena: the inability to reverse mitochondrial dysfunction and profound disturbances in membrane function [1]. **Why Option A is the Correct (False) Statement:** The formation of **large, flocculent, amorphous densities** in the mitochondrial matrix is a definitive sign of **irreversible cell injury** [4]. These densities represent irreversible protein denaturation and lipid peroxidation within the mitochondria, signifying that the "powerhouse" of the cell can no longer recover. In contrast, reversible injury may show only mitochondrial *swelling* or small, transient phospholipid densities [4]. **Analysis of Incorrect Options (Features of Reversible Injury):** * **Option B:** Diminished ATP generation is the earliest consequence of hypoxia/ischemia [1]. It leads to the failure of the Na⁺-K⁺ pump, causing cellular swelling, but is reversible if oxygen is restored [2, 5]. * **Option C:** Plasma membrane blebs, blunting of microvilli, and loosening of intercellular attachments occur due to cytoskeletal damage and osmotic swelling, but the membrane remains structurally intact [3, 4]. * **Option D:** Detachment of ribosomes from the Rough Endoplasmic Reticulum (RER) occurs due to swelling of the ER cisternae. This leads to a decrease in protein synthesis but is reversible [2]. **NEET-PG High-Yield Pearls:** * **Earliest change in reversible injury:** Cellular swelling (Hydropic change/Vacuolar degeneration) [2]. * **Earliest change in irreversible injury:** Plasma membrane damage (allows leakage of intracellular enzymes like Troponin or CK-MB into the blood) [5]. * **Mitochondrial changes:** Swelling = Reversible; Large Amorphous Densities = Irreversible [4]. * **Nuclear changes:** Pyknosis, karyorrhexis, and karyolysis are always indicators of **irreversibility** [3]. **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. 49-50. [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. 51-53. [3] 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. 53. [4] 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. 53-55. [5] 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. 60-61.

Question 920: Dystrophic calcification is seen in which of the following conditions?

A. Myositis ossificans (Correct Answer)
B. Paget's disease
C. Metastasis
D. Sarcoidosis

Explanation: **Explanation:** **Dystrophic calcification** occurs in dead or dying tissues in the presence of **normal** serum calcium levels. It is a localized process resulting from injury or necrosis. **Why Option A is Correct:** **Myositis ossificans** is a classic example of dystrophic calcification. It occurs following trauma to a muscle, leading to intramuscular hemorrhage and subsequent focal tissue necrosis. As the damaged tissue heals, calcium salts deposit in the necrotic area, eventually leading to heterotopic bone formation. Since the underlying cause is local tissue damage and not a systemic mineral imbalance, it is classified as dystrophic. **Why Other Options are Incorrect:** * **B, C, and D (Paget’s disease, Metastasis, Sarcoidosis):** These conditions are associated with **Metastatic calcification**. Metastatic calcification occurs in normal (viable) tissues due to **hypercalcemia** (elevated serum calcium) [1]. * **Paget’s disease** and **Metastasis** cause bone destruction, releasing excess calcium into the blood [1]. * **Sarcoidosis** involves activated macrophages producing Vitamin D, leading to increased calcium absorption. **High-Yield NEET-PG Pearls:** * **Dystrophic Calcification:** Normal serum calcium; seen in areas of necrosis (caseous, liquefactive, coagulative), atherosclerotic plaques, and damaged heart valves. * **Metastatic Calcification:** High serum calcium; typically affects "acid-excreting" organs (Kidneys, Lungs, Gastric mucosa) because the internal alkaline environment favors calcium deposition [2]. * **Morphology:** On H&E stain, both types appear as basophilic (blue-purple), amorphous granular clumps [2]. * **Psammoma bodies:** These are laminated, concentric circles of dystrophic calcification seen in Papillary thyroid carcinoma, Serous cystadenocarcinoma of the ovary, and Meningioma [1]. **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.

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