General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 621: All of the following are stress sensors/regulators for apoptosis, except?

A. Puma
B. BAX (Correct Answer)
C. Noxa
D. BiM

Explanation: ### Explanation The intrinsic (mitochondrial) pathway of apoptosis is regulated by the **BCL-2 family of proteins**, which are divided into three functional groups based on their BCL-homology (BH) domains [1]. **1. Why BAX is the correct answer:** **BAX** (along with BAK) is classified as a **pro-apoptotic effector protein** [1]. These proteins do not act as sensors; instead, they are the "executioners" that undergo conformational changes to form pores in the outer mitochondrial membrane (MOMP) [3]. This leads to the release of Cytochrome C into the cytosol. Therefore, BAX is a downstream effector, not an upstream sensor or regulator. **2. Why the other options are incorrect:** Options A, C, and D (**Puma, Noxa, and BiM**) belong to the **BH3-only protein group**. These are the true **stress sensors/regulators** [1]. * They sense cellular stress (DNA damage, ER stress, or growth factor deprivation) [4]. * Once activated, they "regulate" the pathway by neutralizing anti-apoptotic proteins (like BCL-2 and BCL-xL) and directly activating the effectors (BAX/BAK) [1]. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Anti-apoptotic (Pro-survival) members:** BCL-2, BCL-xL, and MCL-1. They keep the mitochondrial membrane impermeable [1]. * **Pro-apoptotic Effectors:** BAX and BAK ("The Gatekeepers of Death") [1]. * **BH3-only Sensors:** Bad, Bid, Bim, Puma, and Noxa. * **P53 Connection:** In response to DNA damage, the tumor suppressor protein **p53** transcriptionally activates **Puma and Noxa** to initiate apoptosis [2]. * **Cytochrome C:** Once released, it binds to **APAF-1** to form the **Apoptosome**, which activates **Caspase-9** (the initiator caspase of the intrinsic pathway) [1]. **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. 65-67. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 303-304. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310. [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. 80-81.

Question 622: The given pedigree chart most appropriately resembles which of the following diseases?

A. Rett syndrome
B. Duchenne's muscular dystrophy (Correct Answer)
C. Albinism
D. Marfan syndrome

Explanation: ***Duchenne's muscular dystrophy*** - Exhibits classic **X-linked recessive inheritance** pattern with affected males, unaffected carrier females, and **no male-to-male transmission**. - The **dystrophin gene** mutation on the X chromosome causes progressive muscle weakness primarily in boys, matching the pedigree pattern. *Rett syndrome* - Follows **X-linked dominant inheritance** with affected females and is typically **lethal in males**. - Shows a different pattern where affected mothers can pass the condition to both male and female offspring. *Albinism* - Demonstrates **autosomal recessive inheritance** affecting both males and females equally when both parents are carriers. - Would show horizontal pattern in siblings rather than the **vertical male-predominant** pattern seen in X-linked conditions. *Marfan syndrome* - Follows **autosomal dominant inheritance** with **vertical transmission** through generations affecting both sexes equally. - Shows **50% risk** to offspring regardless of gender, unlike the sex-linked pattern in the pedigree.

Question 623: When should EDTA be added to a blood sample?

A. Administered orally several days prior to blood collection.
B. Administered intravenously before drawing blood.
C. EDTA is not an anticoagulant.
D. EDTA is added to the test tube before blood collection. (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. EDTA is added to the test tube before blood collection.** **Underlying Medical Concept:** EDTA (Ethylenediaminetetraacetic acid) is a potent **chelating agent** that binds to calcium ions ($Ca^{2+}$) in the blood. Since calcium is a critical cofactor (Factor IV) in the coagulation cascade [1], its removal prevents the conversion of prothrombin to thrombin, thereby inhibiting clot formation. To ensure immediate anticoagulation and prevent the formation of micro-clots, the blood must come into contact with the anticoagulant the moment it enters the collection tube. Therefore, EDTA is pre-filled in the tube (usually as a spray-dried coating) before the blood is drawn. **Analysis of Incorrect Options:** * **Options A & B:** EDTA is not a medication administered to patients to prevent *in vitro* clotting. While EDTA is used clinically as a treatment for heavy metal poisoning (e.g., lead), it is never administered to "prepare" a patient for a routine blood draw. * **Option C:** This is factually incorrect. EDTA is the "gold standard" anticoagulant for routine hematological investigations (CBC, ESR, HbA1c) because it preserves blood cell morphology better than other agents. **High-Yield Clinical Pearls for NEET-PG:** * **Color Code:** EDTA tubes have **Lavender/Purple** tops. * **Mechanism:** Irreversible chelation of Calcium ($Ca^{2+}$). * **Preferred Use:** Best for Peripheral Blood Smears (PBS) and Complete Blood Counts (CBC) as it prevents platelet aggregation. * **Contraindication:** Not used for coagulation studies (PT/APTT) because it interferes with the very factors being measured; **Sodium Citrate (Blue top)** is used instead. * **Artifact:** Excess EDTA can cause "shrinkage" of RBCs and WBCs, leading to false decreases in Hematocrit (Hct) and Mean Corpuscular Volume (MCV). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130.

Question 624: Which immunoglobulin is primarily found in mucosal secretions?

A. IgG
B. IgA (Correct Answer)
C. IgM
D. IgD

Explanation: **Explanation:** **IgA (Immunoglobulin A)** is the primary antibody found in mucosal secretions such as saliva, tears, colostrum, and the linings of the respiratory, gastrointestinal, and genitourinary tracts. It exists predominantly as a **dimer** in secretions, held together by a J-chain and a **secretory component** that protects it from enzymatic degradation in harsh mucosal environments. Its main function is "immune exclusion," preventing the attachment of pathogens to epithelial surfaces. **Why other options are incorrect:** * **IgG:** This is the most abundant immunoglobulin in the **serum** (not secretions). It is the only antibody that crosses the placenta and provides passive immunity to the fetus. * **IgM:** This is the first antibody produced in a primary immune response [1]. It exists as a **pentamer** in the blood and is the most effective at activating the classical complement pathway [1]. * **IgD:** Found in trace amounts in the serum, it primarily acts as a B-cell antigen receptor on the surface of mature, naive B-lymphocytes. **High-Yield NEET-PG Pearls:** * **Selective IgA Deficiency:** The most common primary immunodeficiency; patients are often asymptomatic but may present with recurrent sinopulmonary infections or giardiasis [2]. * **Breast Milk:** IgA provides critical neonatal intestinal immunity via colostrum. * **Peyer’s Patches:** These are the primary sites in the gut where IgA-producing B-cells are generated. * **Half-life:** IgG has the longest half-life (~23 days), making it the mainstay of secondary immune responses. **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. 154-155. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 249-250.

Question 625: Which stain is used for melanin?

A. Oil red O stain
B. Gomori methenamine silver stain
C. Masson Fontana stain (Correct Answer)
D. Periodic acid-Schiff stain

Explanation: **Explanation:** **Masson Fontana stain** is the correct answer because it is a silver-based stain used to identify **melanin** and argentaffin granules. The underlying principle is the **argentaffin reaction**: melanin is a reducing agent that can reduce silver nitrate to metallic silver without the need for an external reducing agent, resulting in a black/brown deposit. **Analysis of Incorrect Options:** * **Oil Red O (Option A):** This is a fat-soluble dye used to demonstrate **neutral lipids and triglycerides** in frozen sections. It is not used for pigments like melanin. * **Gomori Methenamine Silver (GMS) (Option B):** While also a silver stain, it is primarily used to highlight **fungal cell walls** (e.g., *Pneumocystis jirovecii*) and certain bacteria. * **Periodic Acid-Schiff (PAS) (Option C):** This stain detects **glycogen, mucopolysaccharides, and basement membranes**. It is classically used for diagnosing clear cell carcinomas or fungal infections. **NEET-PG High-Yield Pearls:** 1. **Bleaching Test:** Melanin can be confirmed by "bleaching" it with strong oxidizing agents like hydrogen peroxide or potassium permanganate. If the pigment disappears, it is confirmed as melanin. 2. **Differentiating Pigments:** To distinguish melanin from **Hemosiderin**, use **Prussian Blue (Perl’s stain)**; melanin will be negative, while hemosiderin will turn blue. 3. **IHC Marker:** For malignant melanoma, **S-100** is sensitive, but **HMB-45** and **Melan-A** are more specific immunohistochemical markers.

Question 626: Which is the most common complement protein deficiency?

A. C1
B. C2 (Correct Answer)
C. C3
D. C4

Explanation: **Explanation:** The complement system is a vital component of innate immunity. Among all the inherited complement deficiencies, **C2 deficiency** is the most common (Option B). **Why C2 is the correct answer:** C2 deficiency is an autosomal recessive condition and is the most frequently reported complement protein defect in Western populations. It is often associated with an increased risk of autoimmune diseases, particularly **Systemic Lupus Erythematosus (SLE)**, because C2 is essential for the classical pathway's role in clearing immune complexes. Interestingly, many individuals with C2 deficiency remain asymptomatic because the alternative pathway remains intact to handle bacterial pathogens. **Analysis of Incorrect Options:** * **C1 (Option A):** Deficiency of C1 (C1q, C1r, or C1s) is rare. It is most strongly associated with the development of SLE (over 90% of C1q-deficient individuals develop SLE). [1] * **C3 (Option C):** C3 is the central molecule for all three complement pathways. While not the most common, it is the **most severe** deficiency. Patients present with recurrent, life-threatening pyogenic bacterial infections (e.g., *S. pneumoniae*) and Type III hypersensitivity reactions. * **C4 (Option D):** C4 deficiency is also associated with SLE-like syndromes but is less common than C2 deficiency. **NEET-PG High-Yield Pearls:** 1. **Most common deficiency:** C2. 2. **Most severe deficiency:** C3. 3. **C1 esterase inhibitor deficiency:** Leads to **Hereditary Angioedema** (characterized by low C4 levels). 4. **C5-C9 (MAC) deficiency:** Increases susceptibility to **Neisseria** infections (meningitis and gonorrhea). 5. **CH50 Assay:** Used to screen the classical pathway; it will be low/zero in C1-C8 deficiencies. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 228.

Question 627: Which of the following statements regarding the Human Leukocyte Antigen (HLA) complex is incorrect?

A. Class-I antigens are expressed in all nucleated cells and platelets.
B. Class-II molecules are involved in the induction of helper T-cells.
C. Class-I molecules are homodimers, whereas Class-II molecules are heterodimers. (Correct Answer)
D. Class-I molecules are involved in the induction of cytotoxic T-cells.

Explanation: ### Explanation The **Human Leukocyte Antigen (HLA)** system, encoded by the Major Histocompatibility Complex (MHC) on chromosome 6, is fundamental to immune recognition [1]. **Why Option C is the correct (incorrect statement):** Both Class I and Class II MHC molecules are **heterodimers**, not homodimers [2]. * **Class I molecules** consist of a polymorphic **heavy chain (α chain)** non-covalently linked to a non-polymorphic **$\beta_2$-microglobulin** (encoded on chromosome 15). * **Class II molecules** consist of two polymorphic chains: an **$\alpha$ chain** and a **$\beta$ chain** [1], [2]. The statement is incorrect because it misidentifies Class I as a homodimer. **Analysis of other options:** * **Option A:** Class I antigens (HLA-A, B, C) are indeed expressed on almost **all nucleated cells and platelets** [1]. Notably, they are absent on mature red blood cells. * **Option B:** Class II molecules (HLA-DR, DP, DQ) are primarily expressed on **Antigen-Presenting Cells (APCs)** like dendritic cells, macrophages, and B-cells [1]. They present exogenous peptides to **CD4+ Helper T-cells** [2]. * **Option D:** Class I molecules present endogenous (viral or tumor) antigens to **CD8+ Cytotoxic T-cells**, leading to the destruction of the infected cell. **High-Yield NEET-PG Pearls:** * **MHC Restriction:** CD4+ cells "see" Class II; CD8+ cells "see" Class I (Rule of 8: $4 \times 2 = 8$ and $8 \times 1 = 8$). * **Ankylosing Spondylitis:** Strongly associated with **HLA-B27**. * **Celiac Disease:** Associated with **HLA-DQ2/DQ8**. * **Type 1 Diabetes Mellitus:** Associated with **HLA-DR3/DR4**. * **Structure:** The peptide-binding groove in Class I is formed by $\alpha_1$ and $\alpha_2$ domains; in Class II, it is formed by $\alpha_1$ and $\beta_1$ domains [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. 156-157. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 202-203.

Question 628: Which of the following conditions is associated with coagulative necrosis?

A. Tuberculosis (Correct Answer)
B. Sarcoidosis
C. Cryptococcal infection
D. Gangrene

Explanation: **Explanation:** The correct answer is **Tuberculosis**. While tuberculosis is classically associated with **caseous necrosis**, it is important to understand that caseous necrosis is a specialized form of **coagulative necrosis** [3]. In caseous necrosis, the tissue architecture is completely obliterated (unlike standard coagulative necrosis), but the underlying mechanism involves the denaturation of proteins [2]. In the context of this specific question, TB is the most appropriate choice among the options provided. **Analysis of Options:** * **A. Tuberculosis (Correct):** Characterized by caseous necrosis (cheese-like appearance) [1]. Microscopically, it presents as an eosinophilic, amorphous, granular area surrounded by a granulomatous inflammatory border [4]. * **B. Sarcoidosis:** This is characterized by **non-caseating granulomas**. There is no central necrosis (coagulative or otherwise) in sarcoidosis lesions [4]. * **C. Cryptococcal infection:** Fungal infections like Cryptococcus often lead to **liquefactive necrosis** or may present with a "soap bubble" appearance in the brain due to the gelatinous capsule of the organism. * **D. Gangrene:** While "dry gangrene" is a form of coagulative necrosis, "Gangrene" as a general term often implies **liquefactive necrosis** (wet gangrene) due to superimposed bacterial infection. **NEET-PG High-Yield Pearls:** * **Coagulative Necrosis:** Most common type; seen in all hypoxic cell death/infarcts **except the brain** [3]. * **Liquefactive Necrosis:** Seen in brain infarcts and abscesses (bacterial/fungal). * **Fat Necrosis:** Seen in acute pancreatitis (enzymatic) and breast trauma (non-enzymatic) [2]. * **Fibrinoid Necrosis:** Seen in immune-mediated vascular damage (e.g., Polyarteritis Nodosa, Malignant Hypertension). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 383-384. [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, p. 55. [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. 53-55. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 109.

Question 629: Which of the following is characteristic of irreversible cell injury?

A. Mitochondrial densities (Correct Answer)
B. Cellular swelling
C. Blebs
D. None of the above

Explanation: ### Explanation In cellular pathology, the transition from reversible to irreversible cell injury is defined by two critical phenomena: the inability to reverse mitochondrial dysfunction and profound disturbances in membrane function [1]. **Why "Mitochondrial Densities" is Correct:** The presence of **large, flocculent, amorphous densities** within the mitochondrial matrix is a hallmark of **irreversible cell injury** [1]. These densities represent the precipitation of proteins and the accumulation of calcium (calcium phosphate) due to massive influx into the cell following membrane failure [1]. While small, transient densities can occur in reversible injury, large amorphous densities signify that the cell has passed the "point of no return" and is progressing toward necrosis [1]. **Analysis of Incorrect Options:** * **B. Cellular Swelling:** This is the **first manifestation** of almost all forms of cell injury [1]. It is a **reversible** change caused by the failure of energy-dependent ion pumps (like the Na+/K+ ATPase), leading to an influx of water [1]. * **C. Blebs:** Cytoplasmic blebs (protrusions of the plasma membrane) are considered **reversible** changes [1]. They occur due to cytoskeleton reorganization and loss of microvilli but do not necessarily imply cell death [1]. **High-Yield NEET-PG Pearls:** * **Hallmark of Irreversible Injury:** Severe damage to plasma membranes and lysosomal membranes [1]. * **Mitochondrial Changes:** Mitochondrial *swelling* is reversible; large *amorphous densities* are irreversible [1]. * **Nuclear Changes (Irreversible):** Pyknosis (shrinkage), Karyorrhexis (fragmentation), and Karyolysis (dissolution). * **Light Microscopy:** The earliest sign of reversible injury is "Hydropic change" or "Vacuolar degeneration." **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. 53-62.

Question 630: Which gene is involved in endometrial carcinoma?

A. PTEN (Correct Answer)
B. BRAF
C. KRAS
D. Mismatch repair genes

Explanation: **Explanation:** **PTEN (Phosphatase and Tensin Homolog)** is the most common genetic mutation found in **Type I (Endometrioid) Endometrial Carcinoma**, occurring in approximately 30-80% of cases [1]. PTEN is a tumor suppressor gene located on chromosome 10q23 that normally inhibits the PI3K/AKT signaling pathway [2]. Loss of PTEN function leads to uncontrolled cell proliferation and survival. It is also frequently mutated in the precursor lesion, atypical endometrial hyperplasia [1]. **Analysis of Incorrect Options:** * **BRAF:** Mutations (specifically V600E) are characteristically associated with Papillary Thyroid Carcinoma, Melanoma, and Hairy Cell Leukemia, but not typically with endometrial cancer. * **KRAS:** While KRAS mutations can occur in Type I endometrial carcinoma (approx. 10-30%), PTEN is the more frequent and defining molecular driver for the purpose of standard examinations [1]. * **Mismatch Repair (MMR) Genes:** Defects in MMR genes (MLH1, MSH2, etc.) lead to microsatellite instability (MSI) [1]. While associated with **Lynch Syndrome** (Hereditary Non-Polyposis Colorectal Cancer), which carries a high risk for endometrial cancer, PTEN remains the single most frequently mutated gene in sporadic endometrioid cases [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Endometrial Carcinoma:** Estrogen-dependent, occurs in younger women, associated with PTEN mutations, and has a favorable prognosis [1]. * **Type II (Serous) Endometrial Carcinoma:** Estrogen-independent, occurs in older women, associated with **TP53 mutations**, and has a poor prognosis [1]. * **Cowden Syndrome:** A germline mutation in PTEN that presents with multiple hamartomas and an increased risk of endometrial, breast, and thyroid cancers. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1017-1022. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 294-295.

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Cell Injury and Cell Death

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Adaptations of Cellular Growth

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Accumulations and Deposits

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Acute and Chronic Inflammation

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Tissue Repair and Wound Healing

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Hemodynamic Disorders

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Genetic Disorders

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Environmental Pathology

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Nutritional Diseases

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Molecular Basis of Disease

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