General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 161: Eosinophil production is increased by which of the following cytokines?

A. IL-1
B. IL-6
C. IL-5 (Correct Answer)
D. TNF-A

Explanation: ### Explanation **Correct Option: C (IL-5)** Interleukin-5 (IL-5) is the most specific cytokine for the eosinophil lineage. It is primarily produced by **Th2 cells**, mast cells, and group 2 innate lymphoid cells (ILC2s). IL-5 acts on the bone marrow to stimulate the recruitment, activation, maturation, and survival of eosinophils [2]. In clinical conditions like bronchial asthma or helminthic infections, elevated IL-5 levels are directly responsible for the characteristic peripheral blood eosinophilia [2], [3]. **Analysis of Incorrect Options:** * **IL-1 and TNF-̑ (Options A & D):** These are primary **pro-inflammatory cytokines** produced by macrophages. Their main roles include inducing fever (pyrogens), stimulating the synthesis of acute-phase reactants by the liver, and increasing the expression of adhesion molecules (E-selectin) on vascular endothelium [1]. They do not specifically stimulate eosinophil production. * **IL-6 (Option B):** This is a multifunctional cytokine that acts as a major mediator of the **acute-phase response**. It stimulates the production of C-reactive protein (CRP) and fibrinogen. While it plays a role in B-cell differentiation, it is not the primary driver for eosinophilopoiesis. **NEET-PG High-Yield Pearls:** * **The "Eosinophil Trio":** IL-3, IL-5, and GM-CSF are all involved in eosinophil production, but **IL-5 is the most potent and specific.** [2] * **Eotaxin:** A specific chemokine that recruits eosinophils to the site of inflammation. * **Charcot-Leyden Crystals:** Found in the sputum of asthmatics; these are composed of **Galectin-10** (formerly thought to be lysophospholipase) derived from eosinophil granules. * **Major Basic Protein (MBP):** The primary constituent of eosinophil granules responsible for killing parasites but also causing epithelial damage in asthma [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 211-212. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 688-689. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 210.

Question 162: All of the following are true of red infarction, except?

A. Occurs with venous occlusion
B. Seen in loose tissues
C. Occurs in end arterial occlusion (Correct Answer)
D. Occurs in previously congested tissue

Explanation: **Explanation:** Infarction is classified into two types based on color: **Red (Hemorrhagic)** and **White (Anemic)**. The distinction depends primarily on the nature of the blood supply and the density of the tissue [1]. **Why Option C is the correct answer (The Exception):** Red infarcts occur in tissues with a **dual blood supply** or extensive collateral circulation (e.g., lungs, small intestine). When one vessel is blocked, blood continues to flow from the second source into the necrotic area, causing hemorrhage [1]. In contrast, **end-arterial occlusion** (occlusion in organs with a single blood supply like the heart, spleen, or kidney) leads to **White Infarcts**, as there is no secondary source to bleed into the dead tissue [1]. **Analysis of Incorrect Options:** * **Option A (Venous Occlusion):** This is a classic cause of red infarcts [1]. When venous outflow is obstructed (e.g., testicular torsion), blood stays trapped in the organ, leading to intense congestion and subsequent hemorrhagic necrosis. * **Option B (Loose Tissues):** Red infarcts typically occur in loose, spongy tissues (like the lungs) because the lack of structural density allows blood to easily collect in the necrotic zone [1]. * **Option D (Previously Congested Tissue):** If a tissue is already congested due to sluggish venous outflow, an ensuing arterial infarct will be hemorrhagic (red) because of the pre-existing blood volume [1]. **High-Yield NEET-PG Pearls:** * **White Infarcts:** Occur in solid organs (Heart, Spleen, Kidney) with end-arterial circulation [1]. * **Red Infarcts:** Occur in loose tissues (Lungs), dual supply (Lungs/GI), venous occlusion (Ovary/Testis), and upon **reperfusion** (e.g., after angioplasty) [1]. * **Morphology:** Most infarcts are wedge-shaped, with the apex pointing toward the site of occlusion [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 140-142.

Question 163: What is the mode of genetic inheritance for hemophilia?

A. Sex-linked dominant
B. Sex-linked recessive (Correct Answer)
C. Autosomal dominant
D. Autosomal recessive

Explanation: **Explanation:** **Hemophilia (A and B)** is a classic example of an **X-linked (sex-linked) recessive** disorder [1]. The genes responsible for producing Factor VIII (Hemophilia A) and Factor IX (Hemophilia B) are located on the **X chromosome** [2]. Because it is recessive, the disease primarily affects males (XY), who have only one X chromosome [1]. Females (XX) are typically asymptomatic carriers because their second normal X chromosome compensates for the defective one. **Analysis of Options:** * **Sex-linked dominant (A):** In these disorders (e.g., Alport syndrome, Vitamin D-resistant rickets), an affected father passes the trait to *all* daughters but *no* sons. Hemophilia does not follow this pattern; daughters of affected males are carriers, not necessarily symptomatic [1][3]. * **Autosomal dominant (C):** These involve non-sex chromosomes and appear in every generation (e.g., Marfan syndrome, Achondroplasia) [3]. Hemophilia shows a "criss-cross" inheritance pattern, skipping generations via carrier females. * **Autosomal recessive (D):** These require two copies of the defective gene (e.g., Cystic Fibrosis, Sickle Cell Anemia) [3]. While rare female hemophiliacs can exist (if a carrier mother and affected father mate), the primary mode remains X-linked. **NEET-PG High-Yield Pearls:** 1. **Hemophilia A:** Deficiency of Factor VIII; most common (85% of cases) [2]. 2. **Hemophilia B (Christmas Disease):** Deficiency of Factor IX. 3. **Clinical Presentation:** Characterized by **hemarthrosis** (bleeding into joints) and delayed bleeding after trauma. 4. **Lab Findings:** Prolonged **aPTT** with a normal PT and bleeding time. 5. **Lyonization:** Female carriers may occasionally show mild symptoms due to "unfavorable lyonization" (random inactivation of the normal X chromosome) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 151. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 670-671. [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. 53-54.

Question 164: Which of the following is NOT an inherited coagulation disorder?

A. Protein C deficiency
B. Protein S deficiency
C. Factor V Leiden mutation
D. Lupus anticoagulant (Correct Answer)

Explanation: **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.

Question 165: Which of the following is NOT a B cell marker?

A. CD-15 (Correct Answer)
B. CD-19
C. CD-21
D. CD-23

Explanation: **Explanation:** The correct answer is **CD-15** because it is a marker for **Granulocytes** and **Reed-Sternberg (RS) cells** in Hodgkin Lymphoma, not B cells. **1. Why CD-15 is the correct answer:** CD-15 (also known as Lewis X) is a carbohydrate adhesion molecule. It is characteristically expressed on mature neutrophils, eosinophils, and monocytes. In clinical pathology, its most high-yield association is with **Classical Hodgkin Lymphoma**, where RS cells are typically **CD-15+ and CD-30+**. It is not expressed on normal or neoplastic B-lineage cells. **2. Analysis of B-cell markers (Incorrect Options):** * **CD-19:** This is the most specific and reliable pan-B cell marker [1]. It is expressed from the earliest stages of B-cell development (pro-B cell) until just before terminal differentiation into plasma cells [1]. * **CD-21:** Also known as **CR2 (Complement Receptor 2)**, it is the receptor for the C3d component of complement and the **Epstein-Barr Virus (EBV)** [1], [2]. It is found on mature B cells and follicular dendritic cells [1]. * **CD-23:** This is a low-affinity IgE receptor [1]. It is a key marker used to differentiate **CLL/SLL (CD-23 positive)** from Mantle Cell Lymphoma (CD-23 negative). **High-Yield Clinical Pearls for NEET-PG:** * **Pan-B cell markers:** CD-19, CD-20, CD-22, and PAX-5 (the most specific lineage marker). * **Plasma Cell markers:** CD-138 (Syndecan-1) and CD-38. * **CD-15 & CD-30:** Classic "diagnostic pair" for Reed-Sternberg cells in Hodgkin Lymphoma (except the Nodular Lymphocyte Predominant subtype, which is CD-20+). * **CD-21:** Remember it as the "entry portal" for EBV into B cells [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 598. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 199-200.

Question 166: All the following receptors play a role in phagocytosis EXCEPT-

A. Mannose receptors
B. Scavenger receptors
C. G protein coupled receptor (Correct Answer)
D. Receptors for opsonins

Explanation: **Explanation:** Phagocytosis is a specific form of endocytosis involving the engulfment of large particles (>0.5 μm). The process begins with the **recognition and attachment** of the particle to the leukocyte surface, mediated by specific phagocytic receptors [1]. **Why G Protein-Coupled Receptors (GPCRs) are the correct answer:** GPCRs on leukocytes (such as those for N-formylmethionyl peptides, chemokines, and complement fragments like C5a) are primarily involved in **chemotaxis and leukocyte activation**, not the direct physical engulfment (phagocytosis) of the particle [2]. While they trigger the signaling pathways that increase the efficiency of killing, they do not act as receptors that bind and internalize the microbe. **Analysis of Incorrect Options:** * **Mannose Receptors:** These are lectins that bind terminal mannose and fucose residues on microbial cell walls (patterns not found on mammalian cells). They are classic **Pattern Recognition Receptors (PRRs)** that directly trigger phagocytosis [1]. * **Scavenger Receptors:** These bind a variety of microbes in addition to modified LDL particles. Specifically, CD36 is a well-known scavenger receptor on macrophages that mediates phagocytosis. * **Receptors for Opsonins:** This is the most efficient mechanism for phagocytosis. Microbes are coated with opsonins (e.g., **IgG antibodies, C3b, and plasma lectins**), which then bind to high-affinity receptors like **FcγRI** and **CR1/CR3** on the phagocyte [1], [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Opsonization:** IgG and C3b are the two most important opsonins [1], [3]. * **Engulfment:** This process is dependent on **actin polymerization** (rearrangement of the cytoskeleton) [1]. * **Specific Deficiency:** **Chediak-Higashi Syndrome** involves a defect in phagosome-lysosome fusion due to a mutation in the LYST gene. * **GPCR Role:** Remember, GPCRs "lead the cell to the fight" (chemotaxis), while phagocytic receptors "grab the enemy" (engulfment) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 83-84, 89-91. [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. 163-164. [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. 190-191.

Question 167: Two siblings have osteogenesis imperfecta, but their parents are normal. What is the mechanism of inheritance?

A. Anticipation
B. Genomic imprinting
C. Germline mosaicism (Correct Answer)
D. New mutation

Explanation: **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 168: Which of the following is used as a fungal stain in tissue biopsy sections?

A. PAS (Correct Answer)
B. Alizarin red
C. LPCB
D. Masson Trichrome

Explanation: **Explanation:** **1. Why PAS is the Correct Answer:** **Periodic Acid-Schiff (PAS)** is a classic special stain used in histopathology to detect carbohydrates [1]. Fungi possess a thick cell wall rich in polysaccharides, specifically **chitin and glucans**. The periodic acid oxidizes these carbohydrates to form aldehydes, which then react with the Schiff reagent to produce a brilliant **magenta/purplish-red** color [1]. This makes PAS an excellent tool for visualizing fungal hyphae and spores (e.g., *Candida*, *Aspergillus*) in tissue biopsy sections [1]. **2. Analysis of Incorrect Options:** * **Alizarin Red:** This is a specialized stain used to identify **calcium** deposits in tissue (appearing bright red). It is commonly used in pathologies like calcinosis cutis or atherosclerotic plaques. * **LPCB (Lactophenol Cotton Blue):** While this is a fungal stain, it is used in **microbiology** for wet mounts of fungal cultures, not for histopathological tissue sections. It stains the fungal elements blue against a light background. * **Masson Trichrome:** This is a connective tissue stain used to differentiate between **collagen (blue/green)** and smooth muscle/cytoplasm (red). It is frequently used to assess liver cirrhosis or cardiac fibrosis. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Grocott-Gomori Methenamine Silver (GMS):** This is considered the **gold standard** and most sensitive stain for fungi in tissue, staining them black [1]. * **Mucicarmine:** Specifically used to identify *Cryptococcus neoformans* by staining its polysaccharide capsule bright red [1]. * **PAS-Diastase:** PAS also stains glycogen. To differentiate fungi from glycogen, diastase is added; diastase digests glycogen but leaves fungal walls intact. * **India Ink:** Used for negative staining of *Cryptococcus* in CSF (not tissue). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 362.

Question 169: Which of the following is NOT a tumor that typically undergoes spontaneous resolution?

A. Malignant melanoma
B. Osteogenic sarcoma (Correct Answer)
C. Cholangiocarcinoma
D. Retinoblastoma

Explanation: **Explanation:** The phenomenon of **spontaneous regression** refers to the partial or complete disappearance of a malignant tumor in the absence of specific treatment. This is a rare but well-documented biological event, often attributed to immune system activation, hormonal changes, or cellular differentiation. **Why Osteogenic Sarcoma is the Correct Answer:** **Osteogenic sarcoma (Osteosarcoma)** is a highly aggressive primary bone malignancy characterized by the production of osteoid [1]. It does **not** undergo spontaneous resolution. It requires intensive multimodal therapy, including neoadjuvant chemotherapy and surgical resection [1], as it tends to progress rapidly and metastasize to the lungs [2]. **Analysis of Other Options:** * **Malignant Melanoma:** This is the most classic example of spontaneous regression. It is highly immunogenic; the body’s T-cells can occasionally recognize tumor antigens and mount an immune response that leads to tumor destruction (often seen as "halos" or depigmented areas). * **Retinoblastoma:** Spontaneous regression occurs in approximately 1% of cases, likely due to vascular compromise or apoptosis, often leaving behind a "retinoma" (a benign-appearing calcified mass). * **Cholangiocarcinoma:** While extremely rare, there are documented case reports of spontaneous regression in cholangiocarcinoma, often linked to inflammatory changes or immune modulation. **NEET-PG High-Yield Pearls:** * **Top 4 tumors known for spontaneous regression:** 1. **Neuroblastoma** (Most common; specifically Stage 4S in infants). 2. **Malignant Melanoma.** 3. **Renal Cell Carcinoma** (Regression of pulmonary metastases after nephrectomy). 4. **Choriocarcinoma.** * **Mechanism:** The most common underlying mechanism for spontaneous regression is **immune-mediated cytotoxicity**. * **Neuroblastoma Fact:** Stage 4S neuroblastoma is unique because it can undergo spontaneous maturation into a benign ganglioneuroma or complete involution. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 673-674. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1200-1202.

Question 170: All endothelial cells produce thrombomodulin except those found in which of the following circulations?

A. Hepatic circulation
B. Cutaneous circulation
C. Cerebral microcirculation (Correct Answer)
D. Renal circulation

Explanation: **Explanation:** **Thrombomodulin (TM)** is a critical transmembrane glycoprotein expressed on the surface of vascular endothelial cells. Its primary role is to act as a natural anticoagulant by binding to thrombin, converting it from a procoagulant enzyme into an activator of **Protein C** [1]. Activated Protein C then degrades Factors Va and VIIIa, limiting clot formation [1]. **Why Cerebral Microcirculation is the Correct Answer:** While thrombomodulin is expressed by almost all vascular endothelial cells in the body, it is notably **absent or significantly reduced** in the **cerebral microcirculation** (specifically the small vessels of the blood-brain barrier). This physiological deficiency is thought to be a protective mechanism to prevent excessive anticoagulation in the brain, but it also makes the cerebral microvasculature more susceptible to microvascular thrombosis during inflammatory states or DIC (Disseminated Intravascular Coagulation) [2]. **Analysis of Incorrect Options:** * **A, B, and D (Hepatic, Cutaneous, and Renal circulations):** These vascular beds contain "typical" endothelial cells that express high levels of thrombomodulin to maintain blood fluidity and prevent local thrombus formation. The kidneys and liver, in particular, rely heavily on the Protein C pathway to prevent microvascular occlusion. **NEET-PG High-Yield Pearls:** * **Thrombomodulin Marker:** It is a specific marker for endothelial cells and can be used in immunohistochemistry to identify vascular tumors (e.g., angiosarcoma). * **Soluble Thrombomodulin:** Elevated levels in the plasma serve as a clinical biomarker for **endothelial cell damage** (e.g., in sepsis or vasculitis). * **Mechanism:** Remember the "Switch": Thrombomodulin + Thrombin → Activation of Protein C (Anticoagulant effect) [1]. Without TM, thrombin remains a procoagulant (converting fibrinogen to fibrin). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 583-584. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1266-1268.

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