General Pathology — MCQs

General Pathology Indian Medical PG Practice Questions and MCQs

Question 211: What is the etiology of amyloidosis?

A. Autoimmune
B. T-cell mediated
C. B-cell mediated
D. Unknown (Correct Answer)

Explanation: **Explanation:** The etiology of amyloidosis is fundamentally classified as **Unknown (Idiopathic)** in its primary form [1]. While we understand the pathogenesis—the misfolding of soluble proteins into insoluble, β-pleated sheet fibrils that deposit in extracellular tissues—the precise "trigger" or "etiology" that initiates this protein misfolding in most patients remains unidentified [1]. * **Why 'Unknown' is correct:** In **Primary Amyloidosis (AL type)**, although associated with plasma cell dyscrasias, the reason why specific light chains undergo proteolysis and misfolding into amyloid fibrils in some patients but not others is unknown [1]. Similarly, in **Senile Systemic Amyloidosis**, the reason wild-type transthyretin becomes unstable with age is not fully understood [1]. **Analysis of Incorrect Options:** * **Autoimmune (A):** While Secondary Amyloidosis (AA type) occurs *complicating* chronic inflammatory or autoimmune diseases (like Rheumatoid Arthritis), the autoimmunity itself is a predisposing factor, not the direct etiology of the amyloid fibril [2]. * **T-cell mediated (B):** Amyloidosis is not a Type IV hypersensitivity reaction. T-cells do not play a primary role in the production of amyloidogenic proteins. * **B-cell mediated (C):** While B-cells (plasma cells) produce the precursor light chains in AL amyloidosis, the disease is a disorder of **protein conformation**, not a direct immune-mediated attack by B-cells [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** Amyloid shows **Apple-green birefringence** under polarized light after **Congo Red** staining [2]. * **Structure:** All amyloid types share a common **cross-β-pleated sheet** secondary structure [1]. * **Most Common Type:** Globally, AL (Light chain) is the most common systemic type [1]. * **AA Amyloidosis:** Associated with chronic infections (TB, Osteomyelitis) and chronic inflammation (RA, IBD) [2]. * **Diagnosis:** Abdominal fat pad aspiration or rectal biopsy are preferred screening sites. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 264-268. [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. 136-140.

Question 212: Karyotyping is most commonly performed using which microscopy technique?

A. G banding (Correct Answer)
B. Q banding
C. C banding
D. R banding

Explanation: **Explanation:** **Karyotyping** is the process of pairing and ordering all the chromosomes of an organism. In clinical practice, **G-banding (Giemsa banding)** is the "gold standard" and most commonly used technique because it provides high-quality, permanent preparations that can be visualized under a standard light microscope [1]. 1. **Why G-banding is correct:** Chromosomes are first treated with **Trypsin** (to partially digest proteins) and then stained with **Giemsa stain** [2]. This produces a characteristic pattern of light and dark bands. The **dark bands (G-positive)** are AT-rich, gene-poor, and late-replicating, while the **light bands (G-negative)** are GC-rich, gene-rich, and early-replicating [2]. This pattern allows for the identification of numerical and structural aberrations (e.g., trisomies, translocations). 2. **Analysis of Incorrect Options:** * **Q-banding (Quinacrine):** Uses fluorescent dyes. It was the first banding method developed but requires a fluorescence microscope and the stains fade quickly (photobleaching), making it less practical for routine use. * **C-banding (Centromeric):** Specifically stains **constitutive heterochromatin**, primarily at the centromeres and the distal portion of the Y chromosome. It is used for specific identification of centromeric regions rather than general karyotyping. * **R-banding (Reverse):** Produces a pattern opposite to G-banding (dark bands are GC-rich). It is useful for analyzing the ends of chromosomes (telomeres) which may be pale in G-banding. **High-Yield Clinical Pearls for NEET-PG:** * **Sample Source:** Most common source for postnatal karyotyping is **Peripheral Blood T-lymphocytes** (stimulated by **Phytohemagglutinin**). * **Arrest Stage:** Cells are arrested in **Metaphase** using **Colchicine** (inhibits spindle formation) because chromosomes are most condensed here [2]. * **Resolution:** Standard G-banding identifies ~400–550 bands per haploid set; High-resolution banding (Prophase/Prometaphase) can identify up to 850+ bands [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 167-168. [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. 54-55.

Question 213: Regarding severe combined immunodeficiency, which of the following statements is true?

A. Adenosine deaminase deficiency (Correct Answer)
B. Decreased circulating lymphocytes
C. NADPH oxidase deficiency
D. C1 esterase deficiency

Explanation: **Explanation:** **Severe Combined Immunodeficiency (SCID)** is a group of rare, fatal genetic disorders characterized by the profound failure of both humoral (B-cell) and cellular (T-cell) immune responses [1]. 1. **Why Option A is Correct:** **Adenosine Deaminase (ADA) deficiency** is the second most common cause of SCID (autosomal recessive) [1]. ADA is an enzyme essential for the breakdown of adenosine and deoxyadenosine. Its deficiency leads to the toxic accumulation of **deoxyadenosine triphosphate (dATP)** in lymphocytes [1]. High levels of dATP inhibit ribonucleotide reductase, thereby stalling DNA synthesis and causing apoptosis of precursors for both T-cells and B-cells. 2. **Why Other Options are Incorrect:** * **Option B:** While SCID involves a lack of functional lymphocytes, the hallmark is the **absence of T-cells** and often B-cells/NK cells [1]. "Decreased circulating lymphocytes" is a non-specific finding (lymphopenia) seen in many conditions (e.g., HIV, steroids, malnutrition) and does not define the molecular pathology of SCID as specifically as ADA deficiency. * **Option C:** **NADPH oxidase deficiency** is the cause of **Chronic Granulomatous Disease (CGD)**, where phagocytes cannot produce a respiratory burst to kill catalase-positive organisms. * **Option D:** **C1 esterase inhibitor deficiency** leads to **Hereditary Angioedema**, characterized by recurrent episodes of edema due to overproduction of bradykinin. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause:** X-linked SCID (mutation in the **IL-2 receptor gamma chain**) [1]. * **Radiological Sign:** Absence of thymic shadow on chest X-ray (thymic hypoplasia). * **Clinical Presentation:** Recurrent "monstrous" infections (fungal, viral, bacterial), chronic diarrhea, and failure to thrive in infancy. * **Treatment:** SCID is a pediatric emergency; **Hematopoietic Stem Cell Transplant (HSCT)** is the definitive treatment [2]. ADA deficiency was also the first disease treated with **Gene Therapy** [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 246-247. [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. 167-168.

Question 214: Central to apoptosis is the utilization of?

A. Nitrous oxide
B. Adenyl cyclase
C. Caspases (Correct Answer)
D. c-AMP

Explanation: Apoptosis, or programmed cell death, is a highly regulated process characterized by the activation of specific enzymes that degrade the cell's own DNA and proteins [1]. **1. Why Caspases are correct:** Caspases (**C**ysteine-aspartic proteases) are the central executioners of apoptosis [1]. They exist as inactive zymogens (pro-caspases) and are activated through two main pathways: * **Intrinsic (Mitochondrial) Pathway:** Initiated by the release of Cytochrome c, leading to the activation of **Caspase-9** [2]. * **Extrinsic (Death Receptor) Pathway:** Initiated by FAS-FAS ligand interaction, leading to the activation of **Caspase-8 or 10** [3]. Both pathways converge on the **Executioner Caspases (3, 6, and 7)**, which cleave structural proteins and activate nucleases to fragment DNA [1]. **2. Why other options are incorrect:** * **Nitrous oxide (NO):** Primarily acts as a vasodilator and neurotransmitter. While it can modulate cell survival in specific contexts, it is not a central component of the apoptotic machinery. * **Adenyl cyclase & c-AMP:** These are components of the G-protein coupled receptor (GPCR) signaling pathway. They regulate metabolic processes and secondary messenger signaling rather than the proteolytic cascade of apoptosis. **High-Yield Clinical Pearls for NEET-PG:** * **Caspase-3** is considered the most important executioner caspase. * **BCL-2 and BCL-XL** are anti-apoptotic (stabilize the mitochondrial membrane) [4]. * **BAX and BAK** are pro-apoptotic (form pores in the mitochondrial membrane) [4]. * **Annexin V** is a laboratory marker used to detect apoptosis (binds to Phosphatidylserine flipped on the outer membrane). * Apoptosis does **not** elicit an inflammatory response, unlike necrosis. **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. 64-65. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 67. [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 215: Which test is confirmatory for the diagnosis of Amyloidosis?

A. Diagnostic peritoneal lavage
B. Tongue biopsy
C. Rectal biopsy (Correct Answer)
D. Whole body CT scan

Explanation: **Explanation:** **Amyloidosis** is a disorder characterized by the extracellular deposition of misfolded, insoluble protein fibrils in various tissues [1]. For a definitive diagnosis, tissue biopsy followed by histopathological examination is mandatory. **Why Rectal Biopsy is the Correct Answer:** Rectal biopsy is considered a classic and highly reliable confirmatory test for systemic amyloidosis. The rectum has a rich submucosal vascular plexus where amyloid fibrils tend to deposit. It has a high diagnostic yield (approximately **75-85%**) and is relatively easy to perform. In modern practice, **Abdominal Fat Pad Aspiration** is often the initial screening test due to its non-invasive nature, but rectal biopsy remains a gold-standard confirmatory site when fat aspiration is inconclusive. **Analysis of Incorrect Options:** * **A. Diagnostic Peritoneal Lavage (DPL):** This is used in emergency medicine to detect intra-abdominal hemorrhage following trauma. It has no role in detecting protein deposition diseases. * **B. Tongue Biopsy:** While macroglossia is a hallmark sign of AL amyloidosis [2], a tongue biopsy is painful and carries a risk of significant bleeding and airway compromise. It is rarely the first choice for diagnosis. * **D. Whole Body CT Scan:** CT scans can show organomegaly (e.g., hepatosplenomegaly) but cannot identify microscopic amyloid fibrils. Imaging cannot replace histopathology for confirmation. **NEET-PG High-Yield Pearls:** 1. **Gold Standard Stain:** **Congo Red** stain. Under polarized microscopy, amyloid shows a characteristic **Apple-green birefringence** [1]. 2. **Most Sensitive Initial Screen:** Fine Needle Aspiration (FNA) of **Abdominal Fat Pad** (Yield ~80%). 3. **Most Common Organ Involved:** Kidney (presents as Nephrotic Syndrome). 4. **Most Common Site for Biopsy (Systemic):** Rectum or Abdominal Fat Pad. 5. **Secondary Amyloidosis (AA):** Associated with chronic inflammation (e.g., TB, Rheumatoid Arthritis). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 264-266. [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. 135-136.

Question 216: Tiny linear or arc-shaped bodies, amorphous, brittle and eosinophilic in reaction, found in association with some odontogenic cysts, are called?

A. Civatte bodies
B. Russell bodies
C. Guarnieri bodies
D. Rushton bodies (Correct Answer)

Explanation: ### Explanation **Rushton bodies** are the correct answer. They are unique, eosinophilic, microscopic calcified structures found within the epithelial lining of approximately 10% of **odontogenic cysts**, most commonly in Radicular and Dentigerous cysts. * **Mechanism:** They are thought to be a product of odontogenic epithelium, representing either a form of keratinization or a secretory product of the odontogenic cells that subsequently undergoes calcification. * **Morphology:** They typically appear as linear, straight, curved (hairpin), or circular (arc-shaped) bodies. They are brittle and often show cracks or fractures. #### Analysis of Incorrect Options: * **Civatte bodies:** Also known as colloid or hyaline bodies, these are apoptotic keratinocytes found in the basal layer of the epidermis. They are characteristic of **Lichen Planus** and Lupus Erythematosus. * **Russell bodies:** These are eosinophilic, large, immunoglobulin-containing inclusions found in the cytoplasm of activated **plasma cells**. They are seen in chronic inflammation and Multiple Myeloma. * **Guarnieri bodies:** These are eosinophilic intracytoplasmic inclusion bodies found in cells infected with **Poxvirus** (Smallpox/Vaccinia). #### NEET-PG High-Yield Pearls: * **Rushton bodies** = Odontogenic Cysts (Radicular cyst is the most common site). * **Councilman bodies** = Apoptotic hepatocytes seen in Viral Hepatitis and Yellow Fever. * **Negri bodies** = Intracytoplasmic inclusions in neurons (Purkinje cells) diagnostic of **Rabies**. * **Psammoma bodies** = Laminated calcifications seen in Papillary Thyroid Carcinoma, Meningioma, and Serous Cystadenocarcinoma of the Ovary [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 134-135.

Question 217: Arrange the steps in apoptosis in sequence of occurrence:

A. Removal of BCL-2, Release of cytochrome c in cytoplasm, Activation of APAF-1, Caspase activation (Correct Answer)
B. Caspase activation, Activation of APAF-1, Release of cytochrome c in cytoplasm, Removal of BCL-2
C. Release of cytochrome c in cytoplasm, Activation of APAF-1, Caspase activation, Removal of BCL-2
D. Removal of BCL-2, Activation of APAF-1, Caspase activation, Release of cytochrome c in cytoplasm

Explanation: This question tests the understanding of the **Intrinsic (Mitochondrial) Pathway of Apoptosis**, which is the most common mechanism of programmed cell death in mammals [1]. ### 1. Why the Correct Answer is Right The sequence follows a logical biochemical cascade: * **Removal of BCL-2:** BCL-2 is an anti-apoptotic protein that normally stabilizes the mitochondrial membrane [2]. When a cell is stressed or lacks survival signals, BCL-2 levels drop or are neutralized by pro-apoptotic sensors (like BIM, BID, BAD). * **Release of Cytochrome c:** Without BCL-2, the mitochondrial membrane becomes permeable (via BAX/BAK channels), allowing **Cytochrome c** to leak into the cytoplasm [1]. * **Activation of APAF-1:** Once in the cytosol, Cytochrome c binds to **Apoptotic Protease-Activating Factor-1 (APAF-1)** [1]. * **Caspase Activation:** The Cytochrome c + APAF-1 complex forms the **Apoptosome** (wheel-like structure), which recruits and activates **Caspase-9** (the initiator caspase), eventually leading to the executioner caspase cascade (Caspase-3, 6, 7) [1]. ### 2. Why Other Options are Wrong * **Option B & C:** These suggest that Caspase activation or Cytochrome c release occurs before the loss of BCL-2. BCL-2 is the "gatekeeper"; its removal is the prerequisite for mitochondrial leakage. * **Option D:** This incorrectly places APAF-1 activation before the release of Cytochrome c. APAF-1 remains inactive until it physically binds to Cytochrome c. ### 3. NEET-PG High-Yield Pearls * **Anti-apoptotic proteins:** BCL-2, BCL-XL, MCL-1 (Keep the membrane stable) [1]. * **Pro-apoptotic proteins:** BAX, BAK (Form the pores) [1]. * **Initiator Caspases:** Caspase-9 (Intrinsic), Caspase-8 & 10 (Extrinsic) [1]. * **Executioner Caspases:** Caspase-3 and Caspase-6 [1]. * **Marker of Apoptosis:** Annexin V (binds to Phosphatidylserine flipped to the outer membrane). * **DNA Laddering:** A classic laboratory finding in apoptosis due to internucleosomal cleavage. **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. 64-67. [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. 80-81.

Question 218: What is the initial manifestation of most cell injuries?

A. Cellular swelling (Correct Answer)
B. Necrosis
C. Apoptosis
D. Chromatin condensation

Explanation: **Explanation:** **1. Why Cellular Swelling is Correct:** Cellular swelling (also known as hydropic change or vacuolar degeneration) is the **first manifestation of almost all forms of injury to cells** [1]. The underlying mechanism is the failure of energy-dependent membrane pumps. When a cell is injured (e.g., by hypoxia), ATP production decreases, leading to the failure of the **Naⁱ-Kⁱ ATPase pump**. This results in an accumulation of intracellular sodium and a loss of potassium [1]. The increased osmotic pressure causes an obligatory influx of water into the cell, leading to swelling of the cell and its organelles (like the mitochondria and endoplasmic reticulum) [2]. This is a **reversible** change. **2. Why Other Options are Incorrect:** * **Necrosis:** This is a form of **irreversible** cell injury characterized by membrane breakdown and enzymatic digestion [1]. It occurs much later in the injury sequence than swelling. * **Apoptosis:** This is programmed cell death. While it involves specific morphological changes, it is not the universal "initial" response to generalized cell injury; it is a regulated pathway of cell suicide. * **Chromatin Condensation:** While this occurs in both apoptosis (pyknosis) and necrosis, it is a nuclear sign of advanced injury or death, not the very first cellular change. **Clinical Pearls for NEET-PG:** * **Gross Appearance:** On a macroscopic level, cellular swelling in an organ results in increased weight, pallor, and turgidity. * **Reversibility:** Cellular swelling and fatty change are the two hallmarks of **reversible** cell injury [2]. * **Microscopy:** Under a light microscope, small clear vacuoles may be seen within the cytoplasm; this is referred to as **hydropic change** [1]. * **Sequence of Events:** ATP depletion → Failure of Na-K pump → Influx of Naⁱ and H₂O → Efflux of Kⁱ → Cellular Swelling. **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. 51-53. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 49-50.

Question 219: An elderly male's autopsy reveals brown atrophy of the liver. Microscopic examination shows a finely granular, yellow-brown pigment that frequently encircles the nucleus. Brown atrophy is attributed to the accumulation of which substance?

A. Melanin
B. Hemosiderin
C. Hematin
D. Lipofuscin (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Lipofuscin** **Mechanism and Concept:** Lipofuscin, also known as the **"wear-and-tear"** or **"aging"** pigment, is an insoluble yellowish-brown granular intracellular material [1]. It is a product of **lipid peroxidation** of polyunsaturated lipids of subcellular membranes. It is not harmful to the cell itself but serves as a hallmark of past free radical injury. In states of chronic atrophy (like "Brown Atrophy" of the heart or liver in elderly or malnourished patients), the cell size decreases, making the accumulated pigment appear more concentrated, giving the organ a brown, shrunken appearance [2]. Microscopically, it is classically found in a **perinuclear distribution** [1]. **Why Other Options are Incorrect:** * **A. Melanin:** An endogenous, non-hemoglobin-derived black-brown pigment produced by melanocytes [1]. It is typically found in the skin or eyes, not as a feature of generalized organ atrophy. * **B. Hemosiderin:** A hemoglobin-derived golden-yellow to brown pigment representing aggregates of ferritin micelles [3]. It is seen in areas of hemorrhage or systemic iron overload (hemosiderosis) [4]. Unlike lipofuscin, it stains positive with **Prussian Blue** [4]. * **C. Hematin:** An artifactual pigment (acid hematin) often formed by the action of acid on hemoglobin (e.g., in stomach ulcers or formalin-fixed tissues). It appears as dark brown, microcrystalline material. **High-Yield NEET-PG Pearls:** * **Staining:** Lipofuscin is **Sudanophilic** (stains with Sudan Black B) but does not stain with Prussian Blue (distinguishing it from Hemosiderin). * **Composition:** It consists of polymers of lipids and phospholipids complexed with protein [1]. * **Clinical Association:** Most commonly seen in the **heart and liver** of aging patients or those with severe malnutrition and cancer cachexia [2]. * **Electron Microscopy:** Appears as electron-dense bodies (residual bodies) representing undigested material in lysosomes [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, p. 75. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 47-49. [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. 75-76. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 854-855.

Question 220: Which of the following is a true statement regarding autosomal dominant disorders?

A. They often present early in life.
B. Complete penetrance is common.
C. New germ cell mutations can occur in older fathers. (Correct Answer)
D. The disorder is usually only seen in one generation.

Explanation: **Explanation:** **Autosomal Dominant (AD) Disorders** are characterized by the expression of a disease state even when only one copy of the mutant allele is present [2]. **Why Option C is Correct:** A significant proportion of AD disorders arise from **de novo (new) mutations** rather than inheritance from an affected parent [1]. There is a well-documented correlation between **advanced paternal age** and the occurrence of new germ cell mutations. This is because spermatogonia undergo continuous division throughout life, increasing the cumulative risk of DNA replication errors [1]. Classic examples include **Achondroplasia** and **Apert syndrome**. **Why Other Options are Incorrect:** * **Option A:** Unlike Autosomal Recessive (AR) disorders, which typically manifest in early childhood, AD disorders often have a **delayed onset** (e.g., Huntington’s disease or Polycystic Kidney Disease) [2]. * **Option B:** AD disorders are frequently characterized by **incomplete penetrance** (an individual has the gene but not the phenotype) and **variable expressivity** (individuals with the same gene show different clinical sev-erities). * **Option D:** AD disorders typically show a **vertical pattern of inheritance**, meaning the disease is seen in every generation (unless it is a new mutation or shows incomplete penetrance). AR disorders, conversely, often appear in only one generation (horizontal pattern). **High-Yield NEET-PG Pearls:** * **50% Risk:** An affected parent has a 50% chance of passing the AD trait to each offspring, regardless of sex [2]. * **Structural vs. Functional:** AD disorders usually involve **structural proteins** (e.g., Collagen in Osteogenesis Imperfecta, Fibrillin in Marfan) or **receptors** (e.g., LDL receptor in Familial Hypercholesterolemia). In contrast, AR disorders usually involve **enzyme deficiencies** [3]. * **Anticipation:** Some AD disorders (like Huntington’s) show worsening symptoms or earlier onset in successive generations due to trinucleotide repeat expansions. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1186-1188. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 148-150. [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. 57-58.

Practice by Chapter

Cell Injury and Cell Death

Practice Questions

Adaptations of Cellular Growth

Practice Questions

Accumulations and Deposits

Practice Questions

Acute and Chronic Inflammation

Practice Questions

Tissue Repair and Wound Healing

Practice Questions

Hemodynamic Disorders

Practice Questions

Genetic Disorders

Practice Questions

Environmental Pathology

Practice Questions

Nutritional Diseases

Practice Questions

Molecular Basis of Disease

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free