General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 721: What is the most common odontogenic cyst?

A. Dentigerous cyst
B. Periapical cyst (Correct Answer)
C. Odontogenic keratocyst
D. Gorlin cyst

Explanation: **Explanation:** The **Periapical cyst** (also known as a Radicular cyst) is the most common odontogenic cyst, accounting for approximately 50–75% of all jaw cysts [1]. It is an **inflammatory cyst** that arises from the epithelial rests of Malassez in the periodontal ligament [1]. It typically develops at the apex of a non-vital tooth due to pulp necrosis caused by dental caries or trauma. **Analysis of Options:** * **A. Dentigerous cyst:** This is the most common **developmental** odontogenic cyst. It originates from the reduced enamel epithelium and surrounds the crown of an unerupted tooth (most commonly the mandibular third molar). * **C. Odontogenic Keratocyst (OKC):** Known for its aggressive behavior and high recurrence rate. It arises from the dental lamina and is histologically characterized by a parakeratinized stratified squamous epithelium. It is associated with **Gorlin-Goltz Syndrome**. * **D. Gorlin cyst:** Also known as Calcifying Odontogenic Cyst (COC). It is rare and characterized by the presence of "ghost cells" and focal calcifications. **High-Yield Clinical Pearls for NEET-PG:** * **Most common inflammatory cyst:** Periapical (Radicular) cyst [1]. * **Most common developmental cyst:** Dentigerous cyst. * **Radiological appearance:** Periapical cysts appear as well-defined unilocular radiolucencies at the root apex. * **Histology:** Look for **Rushton bodies** (eosinophilic, linear, or curved inclusions) in the epithelial lining of radicular cysts. * **Syndromic Association:** Multiple OKCs are a hallmark of **Nevoid Basal Cell Carcinoma Syndrome** (Gorlin-Goltz Syndrome). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 741-742.

Question 722: Multiple pulp stones are seen in which of the following conditions?

A. Down syndrome
B. Ehlers-Danlos syndrome (Correct Answer)
C. Marfan syndrome
D. Apert syndrome

Explanation: **Explanation:** **Pulp stones** (denticles) are discrete calcified masses found within the dental pulp chamber or root canals. While they can occur idiopathically with age, multiple pulp stones are a recognized dental manifestation of **Ehlers-Danlos Syndrome (EDS)**, particularly Type I (Gravis type) [1]. **Why Ehlers-Danlos Syndrome is correct:** EDS is a group of heritable connective tissue disorders characterized by defects in collagen synthesis [1]. In the oral cavity, this collagen abnormality affects the dental pulp's vascular and connective tissue integrity, predisposing the patient to the formation of extensive calcifications. Patients with EDS often present with multiple pulp stones, short/malformed roots, and hypoplastic enamel. **Analysis of Incorrect Options:** * **Down Syndrome (Trisomy 21):** Associated with delayed eruption, microdontia, and a high prevalence of periodontal disease, but not specifically linked to multiple pulp stones. * **Marfan Syndrome:** A fibrillin-1 defect characterized by a high-arched palate and dental crowding, but pulp stones are not a classic feature [2]. * **Apert Syndrome:** A craniosynostosis syndrome characterized by "mitten hand" syndactyly and maxillary hypoplasia; it does not typically feature pulp stones. **High-Yield Clinical Pearls for NEET-PG:** * **Gorlin-Goltz Syndrome:** Another important association where multiple pulp stones are seen alongside odontogenic keratocysts (OKCs) and basal cell carcinomas [3]. * **Radiographic Appearance:** Pulp stones appear as radiopaque structures within the radiolucent pulp space. * **Clinical Significance:** They can complicate endodontic treatment (root canals) by blocking access to the canals. * **Other associations:** Dentin dysplasia (Type II) and Tumoral calcinosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 153-155. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 153-154. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1157-1158.

Question 723: Which toll-like receptors are involved in the action of bacterial endotoxins?

A. TLR I
B. TLR II
C. TLR III
D. TLR IV (Correct Answer)

Explanation: **Explanation:** Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) that play a crucial role in the innate immune system by detecting pathogen-associated molecular patterns (PAMPs) [2]. **Why TLR IV is correct:** **TLR IV** is the specific receptor for **Lipopolysaccharide (LPS)**, also known as **bacterial endotoxin** [1], which is found in the outer membrane of Gram-negative bacteria. When LPS binds to TLR IV (with the help of co-factors like CD14 and MD2), it triggers a signaling cascade involving the NF-κB pathway. This leads to the production of pro-inflammatory cytokines (TNF, IL-1), which are responsible for the clinical manifestations of septic shock [1]. **Why other options are incorrect:** * **TLR I:** Usually forms a heterodimer with TLR II to recognize bacterial lipopeptides and peptidoglycans. * **TLR II:** Primarily recognizes bacterial **peptidoglycan**, lipoteichoic acid (Gram-positive bacteria), and fungal zymosan. * **TLR III:** Specifically recognizes **double-stranded RNA (dsRNA)**, making it essential for the immune response against viruses. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** TLRs 1, 2, 4, 5, and 6 are located on the **plasma membrane** (detect extracellular microbes). TLRs 3, 7, 8, and 9 are located in **endosomes** (detect ingested nucleic acids). * **TLR 5:** Recognizes Flagellin (bacterial flagella). * **TLR 7 & 8:** Recognize single-stranded RNA (ssRNA). * **TLR 9:** Recognizes unmethylated CpG DNA (bacterial and viral DNA). * **Transcription Factor:** The common end-point for most TLR signaling is the activation of **NF-κB**, the "master switch" for inflammation. **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. 63-64. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, p. 142.

Question 724: Aneuploidy is due to:

A. Non-disjunction at meiosis (Correct Answer)
B. Mosaicism
C. Deletion
D. Translocation

Explanation: **Explanation:** **Aneuploidy** refers to a numerical chromosomal abnormality where the total number of chromosomes is not an exact multiple of the haploid set (n=23) [2]. Instead of the normal 46 chromosomes, an individual may have 45 (monosomy) or 47 (trisomy) [2]. **Why Option A is correct:** The most common cause of aneuploidy is **non-disjunction** during meiosis (usually Meiosis I). Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly. This results in gametes with an extra chromosome (n+1) or a missing chromosome (n-1). Upon fertilization, these lead to trisomies (e.g., Down Syndrome, 47,XY,+21) or monosomies (e.g., Turner Syndrome, 45,X) [2]. **Why other options are incorrect:** * **B. Mosaicism:** This refers to the presence of two or more populations of cells with different genotypes in one individual, derived from a single zygote [1]. While mosaicism can *involve* aneuploid cells, it is a result of post-zygotic mitotic errors, not the primary mechanism that defines the origin of aneuploidy itself [2]. * **C. Deletion & D. Translocation:** These are **structural** chromosomal abnormalities, not numerical ones. Deletion involves the loss of a segment of a chromosome, while translocation involves the transfer of a segment from one chromosome to another [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Maternal Age:** The risk of meiotic non-disjunction increases significantly with advanced maternal age (especially >35 years) [3]. * **Most common trisomy:** Trisomy 21 (Down Syndrome) [3]. * **Most common cause of spontaneous abortion:** Autosomal trisomy (overall), specifically Trisomy 16 [2]. * **Anaphase Lag:** Another mechanism for aneuploidy where a chromosome fails to connect to the spindle apparatus and is lost during cell division. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 170-171. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169. [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. 92-93.

Question 725: Shock is a circulatory disturbance characterized by

A. Increased blood pressure
B. Decreased volume of circulating blood (Correct Answer)
C. Elevated body temperature
D. Decreased volume of interstitial fluid

Explanation: **Explanation:** **Shock** is defined as a state of systemic hypoperfusion resulting from a mismatch between oxygen supply and demand. The fundamental pathophysiological hallmark of shock is a **decreased effective volume of circulating blood**, which leads to reduced cardiac output and impaired tissue perfusion. This cellular hypoxia eventually results in anaerobic metabolism and multi-organ dysfunction [1]. * **Why Option B is correct:** Whether the cause is hemorrhage (Hypovolemic), pump failure (Cardiogenic), or systemic vasodilation (Distributive), the common denominator is an inadequate volume of blood effectively circulating through the capillary beds to meet metabolic needs [1]. * **Why Option A is incorrect:** Shock is typically characterized by **hypotension** (decreased blood pressure), not hypertension. While compensatory mechanisms (like tachycardia) may maintain BP initially, a drop in BP is a classic clinical sign of progressive shock [2]. * **Why Option C is incorrect:** Most forms of shock (hypovolemic, cardiogenic) present with **hypothermia** and cold, clammy skin. While Septic shock may present with fever, "elevated body temperature" is not a defining characteristic of shock as a whole. * **Why Option D is incorrect:** In many forms of shock (like Septic or Anaphylactic), there is actually an *increase* in interstitial fluid (edema) due to increased capillary permeability, not a decrease [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Stages of Shock:** Non-progressive (compensated), Progressive (tissue hypoperfusion), and Irreversible (cellular injury so severe that survival is impossible) [1]. * **Septic Shock Exception:** Unlike other types, early septic shock often presents with "warm/flushed skin" due to peripheral vasodilation. * **Irreversible Shock:** Characterized by lysosomal enzyme release and the production of **Nitric Oxide (NO)**, which further exacerbates vasodilation [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, p. 144. [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. 150-151.

Question 726: Which of the following is true regarding Chediak-Higashi syndrome?

A. Defect in phagocytosis (Correct Answer)
B. Neutropenia
C. Agammaglobulinemia
D. IgA deficiency

Explanation: **Explanation:** **Chediak-Higashi Syndrome (CHS)** is an autosomal recessive disorder caused by a mutation in the **LYST gene** (Lysosomal Trafficking Regulator). This mutation leads to defective vesicle fusion and intracellular trafficking [1]. **1. Why the correct answer is right:** The hallmark of CHS is the formation of **giant lysosomal granules** in white blood cells [1]. Because these granules cannot fuse properly with phagosomes, the process of **phagolysosome formation** is impaired. This results in a significant **defect in phagocytosis** (specifically the killing phase), leading to recurrent pyogenic infections [1]. **2. Why the incorrect options are wrong:** * **Neutropenia:** While mild neutropenia can occur in CHS due to ineffective granulopoiesis [1], the primary functional pathology defining the disease in the context of "defects of inflammation" is the phagocytic dysfunction. * **Agammaglobulinemia & IgA deficiency:** These are B-cell/humoral immunodeficiencies (e.g., Bruton’s or Selective IgA deficiency). CHS is a disorder of innate immunity (phagocyte function), not antibody production. **3. High-Yield Clinical Pearls for NEET-PG:** * **Microscopy:** Look for pathognomonic **giant azurophilic granules** in neutrophils on a peripheral smear [1]. * **Clinical Tetrad:** 1. **Partial Oculocutaneous Albinism** (due to giant melanosomes) [1]. 2. **Recurrent Pyogenic Infections** (Staph and Strep) [1]. 3. **Progressive Neuropathy** (nerve defects) [1]. 4. **Bleeding tendencies** (defective dense granules in platelets) [1]. * **Accelerated Phase:** Many patients develop a "hemophagocytic lymphohistiocytosis" (HLH)-like syndrome characterized by hepatosplenomegaly and pancytopenia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 245-246.

Question 727: Which of the following conditions is characterized by a microdeletion?

A. Beta thalassemia
B. DiGeorge syndrome (Correct Answer)
C. Marfan's syndrome
D. All of the above

Explanation: **Explanation:** **DiGeorge Syndrome (Correct Answer):** DiGeorge syndrome is a classic example of a **microdeletion syndrome**, specifically involving a submicroscopic deletion on the long arm of chromosome 22 (**22q11.2**) [1]. Because these deletions are too small to be detected by standard karyotyping, they require molecular techniques like **FISH** (Fluorescence In Situ Hybridization) or chromosomal microarray for diagnosis [1]. The deletion results in the maldevelopment of the **3rd and 4th pharyngeal pouches**, leading to the "CATCH-22" clinical constellation: **C**ardiac defects, **A**bnormal facies, **T**hymic hypoplasia (T-cell deficiency), **C**left palate, and **H**ypocalcemia (due to parathyroid aplasia). **Why other options are incorrect:** * **Beta Thalassemia:** This is primarily caused by **point mutations** (more common) or occasionally larger deletions in the $\beta$-globin gene on chromosome 11. It is classified as a single-gene (Mendelian) disorder, not a microdeletion syndrome. * **Marfan’s Syndrome:** This is an **Autosomal Dominant** disorder caused by a mutation in the **FBN1 gene** (encoding Fibrillin-1) on chromosome 15. It is a gene mutation, not a chromosomal microdeletion. **NEET-PG High-Yield Pearls:** * **Velocardiofacial Syndrome:** Also caused by the 22q11.2 deletion; it shares features with DiGeorge but emphasizes facial dysmorphism and palate anomalies [1]. * **Other Microdeletion Syndromes:** Prader-Willi and Angelman syndromes (15q11-q13 deletion) [2], Cri-du-chat (5p deletion), and Williams syndrome (7q11.23 deletion). * **Diagnostic Gold Standard:** FISH is the most frequently tested diagnostic modality for microdeletions in exams [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 172-173. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 181-183.

Question 728: Which stain is used for the identification of fat?

A. Oil red O
B. Sudan black
C. Sudan III
D. Congo red (Correct Answer)

Explanation: ### Explanation The question asks for the identification of fat; however, there appears to be a discrepancy in the provided key. In medical pathology, **Congo red** is the gold standard stain for **Amyloid**, not fat. If we follow the provided key (D), the explanation is as follows: **1. Why Congo Red (Option D) is the "Correct" Answer (Contextual):** In the context of this specific key, Congo red is highlighted. It is used to identify **Amyloid fibrils** [1]. Under ordinary light, amyloid appears pink/red; however, the pathognomonic finding is **apple-green birefringence** when viewed under a **polarized microscope** [1]. If the question intended to ask for amyloid, Congo red is the correct choice. **2. Analysis of Incorrect Options (The Fat Stains):** Options A, B, and C are actually the primary stains used for identifying **lipids (fats)**. They work on the principle of being more soluble in fat than in the solvent they are dissolved in: * **Oil Red O (Option A):** The most common stain for neutral lipids and cholesterols. It stains fat **bright red**. * **Sudan Black B (Option B):** Stains phospholipids and neutral fats **black**. It is also used in hematopathology to differentiate AML (positive) from ALL (negative). * **Sudan III (Option C):** An older stain that colors adipose tissue **orange-red**. **3. NEET-PG High-Yield Clinical Pearls:** * **Processing Requirement:** To stain for fat (Oil Red O/Sudan), you **must** use **frozen sections**. Standard paraffin embedding involves alcohols and xylol, which dissolve fat, leaving behind empty vacuoles. * **Amyloid Stains:** Besides Congo Red, other stains include Thioflavin T (fluorescent) and Crystal Violet (metachromatic). * **Fat Embolism:** In a suspected case of fat embolism (post-long bone fracture), a frozen section of the lung or kidney stained with **Oil Red O** would show intravascular fat globules. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Question 729: Metaplasia occurs in all of the following except:

A. Stem cells (Correct Answer)
B. Squamous cells
C. Columnar cells
D. Transitional cells

Explanation: **Explanation:** Metaplasia is defined as a **reversible change** in which one differentiated cell type (epithelial or mesenchymal) is replaced by another differentiated cell type [1], [3]. **Why "Stem Cells" is the correct answer:** Metaplasia does **not** occur by a differentiated cell (like a squamous cell) physically transforming into another type. Instead, it occurs through the **reprogramming of tissue stem cells** (or undifferentiated mesenchymal cells) [3]. These stem cells are the *source* or the *site* of the genetic reprogramming, but they do not "undergo metaplasia" themselves; rather, they differentiate into a new lineage. Therefore, metaplasia is observed in differentiated tissues, while stem cells are the mediators of this change. **Why the other options are incorrect:** * **Squamous cells:** Can undergo metaplasia. For example, in the urinary bladder (due to chronic irritation from Schistosoma), transitional epithelium can change into squamous cells (**Squamous Metaplasia**) [3]. * **Columnar cells:** Frequently undergo metaplasia. In **Barrett’s Esophagus**, the normal squamous lining of the esophagus changes into columnar (intestinal) cells due to acid reflux [2]. * **Transitional cells:** These cells can be the result or the origin of metaplastic changes in the urothelium [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Most common type:** Squamous metaplasia (e.g., respiratory tract of smokers where columnar cells become squamous) [1], [3]. * **Vitamin A Deficiency:** Can induce squamous metaplasia in the respiratory tract and eyes (Xerophthalmia). * **Connective Tissue Metaplasia:** Formation of bone in soft tissue, known as **Myositis Ossificans**. * **Key Concept:** Metaplasia is usually a protective response but, if the stimulus persists, it can serve as a precursor to **dysplasia** and eventually **cancer** [1], [2]. **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. 49. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 348-349. [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. 91-92.

Question 730: Necrotizing lymphadenitis is seen in which of the following conditions?

A. Hodgkin's disease
B. Kikuchi disease (Correct Answer)
C. Kimura disease
D. Sarcoidosis

Explanation: **Explanation:** **Kikuchi Disease (Histiocytic Necrotizing Lymphadenitis)** is the correct answer. It is a benign, self-limiting condition typically affecting young women. Pathologically, it is characterized by **circumscribed areas of necrosis** in the paracortex of the lymph node [1]. A key diagnostic feature is the presence of **crescentic histiocytes** and abundant karyorrhectic debris (nuclear dust) in the **absence of neutrophils**. This lack of neutrophils is a high-yield distinction from bacterial lymphadenitis [1]. **Analysis of Incorrect Options:** * **Hodgkin’s Disease:** Characterized by the presence of Reed-Sternberg (RS) cells in a background of reactive inflammatory cells [3]. While areas of necrosis can occur in aggressive subtypes, it is not defined as a "necrotizing lymphadenitis." * **Kimura Disease:** A chronic inflammatory condition presenting with painless lymphadenopathy and subcutaneous masses. It is characterized by **follicular hyperplasia, eosinophilic infiltrates, and increased IgE levels**, not necrosis. * **Sarcoidosis:** A classic example of **non-caseating granulomatous inflammation**. The lymph nodes show well-formed granulomas composed of epithelioid cells and multinucleated giant cells (containing Schaumann or Asteroid bodies) without central necrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Kikuchi Disease:** Look for "Crescentic histiocytes," "Plasmacytoid dendritic cells," and "CD8+ T-cell predominance." * **Cat Scratch Disease:** Another cause of necrotizing lymphadenitis, but unlike Kikuchi, it features **stellate (star-shaped) abscesses** with central neutrophils [1]. * **Systemic Lupus Erythematosus (SLE):** Can mimic Kikuchi disease histologically; however, SLE lymphadenopathy typically shows **hematoxylin bodies** and DNA deposition in vessel walls (Azzopardi phenomenon) [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, pp. 592-593. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 554-555. [3] 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. 618.

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Cell Injury and Cell Death

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Hemodynamic Disorders

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Genetic Disorders

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Molecular Basis of Disease

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