Inflammation and Repair — MCQs
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A 24-year-old delivery driver sustains a wide abrasion over his left elbow resulting in the total loss of epidermis over a large area of his left arm. One month later, the abrasion has healed with regrowth of the epidermis. Which of the following mechanisms accounts for the restoration of the epidermis over the abraded area?
Systemic features of inflammation, such as fever and hypotension, are primarily mediated by which of the following types of molecules?
A 68-year-old man with prostate cancer and bone metastases presents with shaking chills and fever. The peripheral WBC count is 1,000/mL (normal = 4,000 to 11,000/mL). Which of the following terms best describes this hematologic finding?
What are the central cellular players in the repair process?
Which of the following structures exhibits immediate transient type of increased vascular permeability in acute inflammation?
Which mechanism plays the dominant role in regenerative repair after chronic liver injury or inflammation?
Which of the following statements regarding the SIRS diagnostic criteria is incorrect?
"CACHECTIN" is produced by?
What is the primary action of VEGF?
A 58-year-old man had chest pain persisting for 4 hours. Radiographic imaging showed an infarction involving a 4-cm area of the posterior left ventricular free wall. Laboratory findings showed serum creatine kinase of 600 U/L. Which of the following pathologic findings would most likely be seen in the left ventricular lesion 1 month later?
Inflammation and Repair Indian Medical PG Practice Questions and MCQs
Question 111: A 24-year-old delivery driver sustains a wide abrasion over his left elbow resulting in the total loss of epidermis over a large area of his left arm. One month later, the abrasion has healed with regrowth of the epidermis. Which of the following mechanisms accounts for the restoration of the epidermis over the abraded area?
- A. Growth of epidermis from hair follicles and sweat glands in the dermis (Correct Answer)
- B. Migration of endothelial cells from newly grown capillaries
- C. Transformation of dermal fibroblasts into epidermal cells
- D. Transformation of macrophages into epidermal cells
Explanation: ### Explanation The correct answer is **A. Growth of epidermis from hair follicles and sweat glands in the dermis.** **Mechanism of Re-epithelialization:** In a wide abrasion where the entire surface epidermis is lost, healing occurs through **re-epithelialization**. The primary sources of new epithelial cells are the **skin appendages** (hair follicles, sebaceous glands, and sweat glands) located deep within the dermis [1]. These structures are lined by epithelial cells that act as a reservoir of stem cells [1]. When the surface is denuded, these cells proliferate and migrate upward and outward to form a new epidermal layer. This is why superficial burns and abrasions heal faster than deep-seated wounds where appendages are destroyed. **Why the other options are incorrect:** * **Option B:** Endothelial cells are responsible for **angiogenesis** (forming new blood vessels) and the formation of granulation tissue, but they cannot differentiate into epithelial cells [2]. * **Option C:** Fibroblasts are mesenchymal cells that produce collagen and extracellular matrix for scar formation [2]. They do not transform into ectodermal derivatives like epidermal cells. * **Option D:** Macrophages are inflammatory cells derived from monocytes [2]. Their role is phagocytosis and the secretion of growth factors (like TGF-β) to orchestrate repair; they do not transdifferentiate into skin cells. **NEET-PG High-Yield Pearls:** * **Regeneration vs. Repair:** Regeneration involves the replacement of damaged components with the same cell type (e.g., epidermis), whereas repair involves scarring (fibrosis) [3]. * **Labile Cells:** Epidermal cells are "labile cells," meaning they continuously divide throughout life [3]. * **Wound Contraction:** Mediated by **myofibroblasts**, this process significantly reduces the size of large wounds during healing by second intention. * **Key Growth Factor:** **EGF (Epidermal Growth Factor)** and **TGF-α** are the primary stimulators of keratinocyte migration and proliferation during re-epithelialization [2]. **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. 104-105. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 113-115.
Question 112: Systemic features of inflammation, such as fever and hypotension, are primarily mediated by which of the following types of molecules?
- A. Lipoxins
- B. Cytokines (Correct Answer)
- C. Histamine
- D. Leukotrienes
Explanation: ### Explanation The systemic response to inflammation, often referred to as the **Acute Phase Response**, is primarily mediated by **Cytokines**, specifically **TNF-α, IL-1, and IL-6** [1]. **Why Cytokines are the Correct Answer:** * **Fever:** IL-1 and TNF-α act as endogenous pyrogens [2]. They travel to the hypothalamus and stimulate the synthesis of Prostaglandins (PGE2), which resets the thermostatic set-point to a higher level [1]. * **Hypotension/Shock:** In severe systemic inflammation (Sepsis), high levels of TNF-α cause myocardial suppression and systemic vasodilation, leading to hypotension and septic shock [1]. * **Acute Phase Proteins:** IL-6 stimulates the liver to synthesize proteins like C-reactive protein (CRP) and Fibrinogen [1]. **Analysis of Incorrect Options:** * **A. Lipoxins:** These are anti-inflammatory lipids derived from arachidonic acid. They serve to **resolve** inflammation by inhibiting neutrophil recruitment. * **C. Histamine:** This is a vasoactive amine stored in mast cells. It acts **locally** and immediately to cause vasodilation and increased vascular permeability (redness and swelling), but it does not mediate systemic features like fever [2]. * **D. Leukotrienes:** These are arachidonic acid metabolites (LTC4, LTD4, LTE4) primarily involved in bronchoconstriction and increased vascular permeability, particularly in asthma and immediate hypersensitivity reactions [2]. **NEET-PG High-Yield Pearls:** * **IL-1:** The primary mediator of fever [2]. * **IL-6:** The most potent stimulator of **Acute Phase Reactants** (CRP, Ferritin, Fibrinogen, Hepcidin) [1]. * **TNF-α:** The chief mediator of **Septic Shock** and cachexia (wasting syndrome) [1]. * **ESR:** Elevated during inflammation because Fibrinogen causes RBCs to form stacks (Rouleaux). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 110-111. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101.
Question 113: A 68-year-old man with prostate cancer and bone metastases presents with shaking chills and fever. The peripheral WBC count is 1,000/mL (normal = 4,000 to 11,000/mL). Which of the following terms best describes this hematologic finding?
- A. Leukocytosis
- B. Leukopenia (Correct Answer)
- C. Neutrophilia
- D. Pancytopenia
Explanation: ### Explanation **1. Why Leukopenia is Correct:** The patient’s peripheral White Blood Cell (WBC) count is **1,000/mL**, which is significantly below the normal reference range of **4,000 to 11,000/mL**. The medical term for a decrease in the total number of circulating white blood cells is **Leukopenia** [1]. In this clinical scenario, the leukopenia is likely secondary to **myelophthisis** (bone marrow infiltration by metastatic prostate cancer), which impairs normal hematopoiesis, or potentially due to overwhelming sepsis causing rapid consumption of leukocytes [1]. **2. Why the Other Options are Incorrect:** * **A. Leukocytosis:** This refers to an *increase* in the total WBC count (>11,000/mL), typically seen in acute infections or inflammation. * **C. Neutrophilia:** This is a specific increase in the absolute *neutrophil* count. While neutrophils are a subset of WBCs, the question provides the total WBC count, and the value indicates a decrease, not an increase. * **D. Pancytopenia:** This term describes a simultaneous decrease in all three hematologic cell lines: Red Blood Cells (anemia), White Blood Cells (leukopenia), and Platelets (thrombocytopenia). While this patient might have pancytopenia due to marrow infiltration, the question *only* provides the WBC count; therefore, "Leukopenia" is the most accurate description of the specific finding provided. **3. NEET-PG High-Yield Pearls:** * **Myelophthisic Anemia:** Characterized by the displacement of hemopoietic bone marrow tissue by fibrosis, tumors (like prostate/breast cancer), or granulomas. * **Prostate Cancer Metastasis:** Usually **osteoblastic** (bone-forming) rather than osteolytic, often presenting with elevated Serum Alkaline Phosphatase (ALP). * **Critical Values:** A WBC count <1,000/mL significantly increases the risk of opportunistic infections and life-threatening sepsis [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 110-111.
Question 114: What are the central cellular players in the repair process?
- A. Platelets
- B. Macrophages (Correct Answer)
- C. Neutrophils
- D. Fibroblasts
Explanation: **Explanation:** The repair process (healing by fibrosis or regeneration) is a highly coordinated event where **Macrophages** act as the "central directors." [1] While multiple cells participate, macrophages are indispensable because they orchestrate the transition from inflammation to repair. **Why Macrophages are the Correct Answer:** Macrophages (specifically the **M2 phenotype**) perform three critical functions in repair: [1], [3] 1. **Debridement:** They clear apoptotic cells, debris, and microbes. [1] 2. **Cytokine Production:** They secrete growth factors like **TGF-̢**, PDGF, and FGF, which are essential for fibroblast recruitment and collagen synthesis. [2] 3. **Angiogenesis:** They release VEGF to stimulate the formation of new blood vessels, providing nutrients for the healing tissue. [2] **Analysis of Incorrect Options:** * **Platelets (A):** These are the first responders involved in **hemostasis** (clot formation). While they release initial growth factors (PDGF), they do not manage the long-term remodeling or debridement phases. * **Neutrophils (C):** These are the hallmark of **acute inflammation**. Their primary role is phagocytosis of bacteria; however, they usually disappear (via apoptosis) before the actual repair process begins. [1] * **Fibroblasts (D):** These are the "workhorses" that synthesize collagen and the extracellular matrix. While crucial for structural integrity, they act under the **instruction and signaling** of macrophages. [2] **High-Yield NEET-PG Pearls:** * **TGF-̢** is the most important cytokine for synthesis and deposition of connective tissue proteins. [2] * **M1 Macrophages** are pro-inflammatory (microbicidal), while **M2 Macrophages** are anti-inflammatory and promote repair. [1], [3] * **Granulation tissue** (the hallmark of early repair) is characterized by fibroblasts, new thin-walled capillaries (angiogenesis), and scattered macrophages. [1], [4] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 115. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 105-106. [4] 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. 105-106.
Question 115: Which of the following structures exhibits immediate transient type of increased vascular permeability in acute inflammation?
- A. Venules (Correct Answer)
- B. Capillaries
- C. Arterioles
- D. None of the above
Explanation: **Explanation:** The hallmark of acute inflammation is increased vascular permeability, leading to the formation of an inflammatory exudate. The **immediate transient response** is the most common pattern of increased permeability [1]. **1. Why Venules are correct:** The immediate transient response is primarily mediated by chemical mediators like **histamine, bradykinin, and leukotrienes** [2]. These mediators cause **endothelial cell contraction**, which creates intercellular gaps [1]. This process occurs almost exclusively in the **small venules** (20–60 μm in diameter) because these vessels have a higher density of receptors for histamine and other mediators compared to capillaries or arterioles [1]. The response develops rapidly (within minutes) and is short-lived (lasting 15–30 minutes) [1]. **2. Why other options are incorrect:** * **Capillaries:** While capillaries can be involved in **delayed prolonged leakage** (e.g., in thermal burns or radiation injury) or **direct endothelial injury**, they are not the primary site for the mediator-induced immediate transient response [1]. * **Arterioles:** Arterioles generally do not show increased permeability via endothelial contraction [1]. Their primary role in inflammation is vasodilation (mediated by Nitric Oxide and Prostaglandins) to increase blood flow to the site of injury [3]. **High-Yield Facts for NEET-PG:** * **Mechanism:** Endothelial cell contraction is the most common mechanism of vascular leakage [1]. * **Delayed Prolonged Response:** Involves both **venules and capillaries** (e.g., sunburn). It starts after 2–12 hours and lasts for several days. * **Direct Endothelial Injury:** Affects **all levels of microvasculature** (arterioles, capillaries, and venules) and results in immediate sustained leakage. * **Transcytosis:** Increased transport of fluids and proteins through the endothelial cell (via the vesiculovacuolar organelle) is stimulated by **VEGF**. **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. 187-188. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85.
Question 116: Which mechanism plays the dominant role in regenerative repair after chronic liver injury or inflammation?
- A. Proliferation of the residual hepatocytes
- B. Repopulation from progenitor cells (Correct Answer)
- C. Replacement of parenchymal cells by collagen
- D. Both proliferation of residual hepatocytes and repopulation from progenitor cells
Explanation: **Explanation:** The liver possesses a remarkable capacity for regeneration, but the mechanism depends entirely on the nature and duration of the injury [3]. **1. Why Option B is Correct:** In scenarios of **chronic liver injury** or inflammation (such as chronic viral hepatitis or alcoholic liver disease), the regenerative capacity of mature hepatocytes is exhausted due to "replicative senescence." [2] When hepatocytes can no longer proliferate, the liver activates a backup mechanism: **repopulation from progenitor cells** (historically called **Oval cells** in rodents) [1]. These bipotential stem cells reside in the **Canals of Hering** and can differentiate into both hepatocytes and biliary epithelial cells to restore liver mass. **2. Why the other options are incorrect:** * **Option A:** Proliferation of residual hepatocytes is the dominant mechanism in **acute** liver injury (e.g., partial hepatectomy or toxin-induced acute necrosis) [1]. In these cases, the remaining mature hepatocytes enter the cell cycle to restore the liver. * **Option C:** Replacement by collagen refers to **fibrosis/scarring**. While this occurs in chronic injury, it is a pathological process of "repair by connective tissue" rather than "regenerative repair" of the functional parenchyma [3]. * **Option D:** While both occur in the liver generally, the question specifies **chronic** injury, where progenitor cell activation becomes the *dominant* and defining pathway because mature hepatocyte proliferation is impaired [2]. **Clinical Pearls for NEET-PG:** * **Niche:** Liver progenitor cells are located in the **Canals of Hering**. * **Acute Injury:** Regeneration via **Hepatocyte Hyperplasia** (Mature cells). * **Chronic Injury:** Regeneration via **Progenitor Cells** (Stem cells). * **Key Growth Factors:** HGF (Hepatocyte Growth Factor) and IL-6 are critical mediators of the priming phase in liver regeneration [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. 108-109. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 833-834. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 113-115.
Question 117: Which of the following statements regarding the SIRS diagnostic criteria is incorrect?
- A. Bandemia >10%
- B. Leukocytosis >12,000 cells/mm³
- C. Respiratory rate >20 breaths/min
- D. Bandemia <5% (Correct Answer)
Explanation: **Explanation:** Systemic Inflammatory Response Syndrome (SIRS) is a clinical syndrome characterized by a robust inflammatory state in response to either infectious or non-infectious insults (e.g., trauma, burns, pancreatitis) [1]. The diagnosis requires the presence of **at least two** of the following four criteria: 1. **Temperature:** $>38^\circ\text{C}$ ($100.4^\circ\text{F}$) or $<36^\circ\text{C}$ ($96.8^\circ\text{F}$). 2. **Heart Rate:** $>90$ beats per minute. 3. **Respiratory Rate:** $>20$ breaths per minute OR $\text{PaCO}_2 <32\text{ mmHg}$. 4. **White Blood Cell Count:** $>12,000/\text{mm}^3$, $<4,000/\text{mm}^3$, or **$>10\%$ immature (band) forms** [2]. **Why Option D is the Correct Answer (Incorrect Statement):** The criteria specifically define **Bandemia as >10%**. A value of <5% is considered within the normal physiological range and does not indicate the "left shift" (release of immature neutrophils) typically seen in a systemic inflammatory response [2]. **Analysis of Other Options:** * **Option A (Bandemia >10%):** This is a correct component of the WBC criteria for SIRS. * **Option B (Leukocytosis >12,000):** This is a standard threshold for defining the inflammatory response in the blood [2]. * **Option C (RR >20):** Tachypnea is one of the earliest clinical signs of systemic distress and is a valid SIRS criterion. **High-Yield Pearls for NEET-PG:** * **Sepsis vs. SIRS:** Sepsis is defined as SIRS + a documented or suspected source of infection [1]. * **qSOFA Score:** In modern practice (Sepsis-3), the qSOFA score (Altered mental status, Systolic BP $\leq 100$, RR $\geq 22$) is often used to identify patients at risk, but SIRS criteria remain high-yield for pathology and surgery exams. * **Left Shift:** The presence of band cells (immature neutrophils) signifies that the bone marrow is rapidly releasing cells to combat inflammation [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 81-82. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 110-111.
Question 118: "CACHECTIN" is produced by?
- A. macrophage (Correct Answer)
- B. neutrophils
- C. basophils
- D. eosinophils
Explanation: **Explanation:** **Cachectin** is the historical name for **Tumor Necrosis Factor-alpha (TNF-α)**. It was given this name because of its potent ability to induce **cachexia** (profound weight loss and muscle wasting) in chronic diseases and malignancy by suppressing appetite and inhibiting lipoprotein lipase [1]. 1. **Why Macrophages are correct:** Activated **macrophages** (and monocytes) are the primary cellular source of TNF-α/Cachectin [1]. When macrophages encounter bacterial endotoxins (LPS) or immune complexes, they secrete this cytokine to mediate the acute inflammatory response, stimulate the endothelium, and induce systemic effects like fever [1]. 2. **Why other options are incorrect:** * **Neutrophils:** While neutrophils are the hallmark of acute inflammation and respond to TNF-α, they are not the primary producers of it. Their main role is phagocytosis and the release of reactive oxygen species (ROS) and lysosomal enzymes. * **Basophils & Eosinophils:** These are primarily involved in Type I hypersensitivity reactions and parasitic infections. Eosinophils are characterized by Major Basic Protein (MBP), while basophils release histamine. Neither is a significant source of Cachectin. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Cachexia:** TNF-α causes wasting by mobilizing triglycerides from fat stores and suppressing appetite via the hypothalamus [1]. * **Dual Role:** In low concentrations, TNF-α acts locally on endothelium; in high concentrations, it causes **Septic Shock** (myocardial suppression and DIC) [1]. * **Key Cytokine Pair:** TNF and IL-1 are the "master regulators" of the acute phase response [1]. * **Granuloma Formation:** TNF-α is essential for the formation and maintenance of granulomas in Tuberculosis. This is why anti-TNF drugs (e.g., Infliximab) can lead to the reactivation of latent TB. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 97-111.
Question 119: What is the primary action of VEGF?
- A. Vasodilation
- B. Angiogenesis (Correct Answer)
- C. Fibrogenesis
- D. Chemotaxis
Explanation: **Vascular Endothelial Growth Factor (VEGF)** is the most critical driver of **angiogenesis** (the formation of new blood vessels from pre-existing ones) in both physiological states and pathological conditions like wound healing, chronic inflammation, and tumor growth [2]. It primarily acts by stimulating the proliferation, migration, and survival of endothelial cells. It also increases vascular permeability (originally named Vascular Permeability Factor), allowing plasma proteins to extravasate and provide a scaffold for new vessel growth [1]. **Analysis of Options:** * **A. Vasodilation:** While VEGF can induce vasodilation indirectly by stimulating the release of Nitric Oxide (NO), its *primary* and defining role in pathology is structural vessel growth (angiogenesis). Histamine and Prostaglandins are the classic mediators of vasodilation. * **C. Fibrogenesis:** This is primarily mediated by **TGF-β** (Transforming Growth Factor-beta) and PDGF [4]. These factors stimulate fibroblast proliferation and collagen synthesis. * **D. Chemotaxis:** This refers to the movement of leukocytes toward a chemical gradient. Key chemotactic agents include **C5a, LTB4, and IL-8**. **High-Yield Clinical Pearls for NEET-PG:** * **VEGF-A** is the major isoform involved in angiogenesis. * **Hypoxia** is the most important inducer of VEGF production, mediated via **HIF-1α** (Hypoxia-Inducible Factor) [3]. * **Clinical Correlation:** Anti-VEGF antibodies (e.g., **Bevacizumab**) are used in cancer therapy to "starve" tumors, and in ophthalmology (e.g., **Ranibizumab**) to treat wet Age-Related Macular Degeneration (AMD) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [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. 88-89. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 313-314. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 115-116.
Question 120: A 58-year-old man had chest pain persisting for 4 hours. Radiographic imaging showed an infarction involving a 4-cm area of the posterior left ventricular free wall. Laboratory findings showed serum creatine kinase of 600 U/L. Which of the following pathologic findings would most likely be seen in the left ventricular lesion 1 month later?
- A. Chronic inflammation
- B. Coagulative necrosis
- C. Complete resolution
- D. Fibrous scar (Correct Answer)
Explanation: **Explanation:** The clinical presentation of prolonged chest pain, elevated creatine kinase, and imaging evidence of infarction confirms a **Myocardial Infarction (MI)**. The question focuses on the **temporal evolution of tissue repair** following permanent cell injury in the heart. **1. Why "Fibrous scar" is correct:** The heart is composed of **permanent cells** (cardiac myocytes) that lack the capacity for regenerative division. When these cells undergo ischemic necrosis, they cannot be replaced by new myocytes [1]. Instead, the area undergoes healing by **secondary intention**, where the necrotic tissue is cleared by macrophages and replaced by granulation tissue, which eventually matures into a **dense collagenous fibrous scar** [2]. This process typically peaks and stabilizes between **2 to 8 weeks** post-infarction. By 1 month, the transition from granulation tissue to a firm scar is well underway [1]. **2. Why other options are incorrect:** * **A. Chronic inflammation:** While macrophages are present during the repair phase, "chronic inflammation" as a primary finding usually implies a persistent stimulus (like infection or autoimmunity). In MI, the inflammation is a transient response to clear debris [3]. * **B. Coagulative necrosis:** This is the *initial* microscopic change seen within the first 24–72 hours [2]. By 1 month, the necrotic debris has been removed by phagocytes. * **C. Complete resolution:** This occurs only in tissues with **labile or stable cells** (e.g., liver or skin) where the connective tissue framework remains intact. Since myocytes are permanent cells, resolution is impossible. **Clinical Pearls for NEET-PG:** * **0–24 hours:** Coagulative necrosis, wavy fibers, contraction bands [2]. * **1–3 days:** Dense neutrophilic infiltrate (Risk of post-MI pericarditis) [2]. * **3–7 days:** Macrophage infiltration (Peak risk of **ventricular wall rupture** due to tissue softening) [1]. * **1–2 weeks:** Granulation tissue appearance [1]. * **>2 weeks:** Progressive fibrosis and scarring [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, pp. 552-554. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, p. 552. [3] 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. 147-148.
Practice by Chapter
Acute Inflammation: Vascular Events
Practice Questions
Acute Inflammation: Cellular Events
Practice Questions
Chemical Mediators of Inflammation
Practice Questions
Chronic Inflammation
Practice Questions
Granulomatous Inflammation
Practice Questions
Systemic Effects of Inflammation
Practice Questions
Wound Healing
Practice Questions
Tissue Regeneration
Practice Questions
Fibrosis and Repair
Practice Questions
Resolution of Inflammation
Practice Questions
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