General Pathology Practice Questions

Q: A couple is referred to the physician because their first three pregnancies have ended in spontaneous abortion. Chromosomal analysis reveals that the wife has two cell lines in her blood, one with a missing X chromosome (45,X) and the other normal (46,XX). Her chromosomal constitution can be described as?

Mosaic. ### Explanation **Correct Option: D. Mosaic** **Mosaicism** is defined as the presence of two or more populations of cells with different genotypes in one individual who has developed from a **single fertilized egg (zygote)** [1]. In this case, the wife has two cell lines (45,X and 46,XX) originating from the same zygote. This typically occurs due to **post-zygotic mitotic non-disjunction** or anaphase lag during early embryonic development [1]. Mosaic Turner syndrome (45,X/46,XX) often presents with a milder phenotype than classic Turner syndrome (45,X), allowing for secondary sexual characteristics and, occasionally, the ability to conceive, though it is a known cause of recurrent spontaneous abortions. **Why Incorrect Options are Wrong:** * **A. Chimeric:** Chimerism involves two or more cell lines derived from **different zygotes** (e.g., the fusion of two embryos or exchange of cells between twins in utero). * **B. Monoploid:** This refers to a cell or organism having a single set of chromosomes (n). In humans, only gametes are monoploid. * **C. Trisomic:** This refers to the presence of an extra chromosome (e.g., Trisomy 21). The patient in the question has a cell line with a missing chromosome (monosomy), not an extra one. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Mosaicism results from **post-zygotic** errors; Chimerism results from **fusion** of different zygotes. * **Germline Mosaicism:** If a mutation occurs in a germ cell precursor, the individual is phenotypically normal but can pass the mutation to multiple offspring (e.g., Osteogenesis Imperfecta, Duchenne Muscular Dystrophy). * **Turner Syndrome:** 45,X/46,XX is the most common mosaic pattern in Turner syndrome [1]. These patients have a higher risk of premature ovarian failure and recurrent pregnancy loss. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169.

Q: Sudden decrease in atmospheric pressure in deep sea divers resulting in "bends" and "chokes" are features of which condition?

Air embolism. **Explanation:** The clinical scenario describes **Decompression Sickness (DCS)**, also known as "Caisson disease." This condition occurs due to **Henry’s Law**, which states that the solubility of a gas in a liquid is proportional to its partial pressure. 1. **Why Air Embolism is correct:** When a diver is deep underwater, high atmospheric pressure causes large amounts of Nitrogen to dissolve into the blood and tissues. If the diver ascends too rapidly (sudden decrease in pressure), the Nitrogen comes out of solution and forms **gas bubbles** in the blood and tissues. These bubbles act as **air emboli**, obstructing blood flow. * **"The Bends":** Bubbles in the joints and muscles causing severe pain. * **"The Chokes":** Bubbles in the pulmonary capillaries causing shortness of breath, chest pain, and cough. 2. **Why other options are incorrect:** * **Fat embolism:** Typically occurs after long bone fractures (e.g., femur) where marrow fat enters the circulation; it is not related to atmospheric pressure changes. * **Aspiration pneumonia:** Caused by inhaling foreign material (vomit/food) into the lungs, leading to inflammation/infection. * **Gangrene:** This is tissue death due to lack of blood supply or infection. While severe DCS can lead to necrosis (e.g., dysbaric osteonecrosis), it is a late complication, not the immediate mechanism of "bends and chokes." **NEET-PG High-Yield Pearls:** * **Nitrogen Narcosis:** Occurs at depth (high pressure) due to the anesthetic effect of nitrogen; often called "Rapture of the Deep." * **Treatment:** The definitive treatment for Decompression Sickness is **Hyperbaric Oxygen Therapy (HBOT)** in a recompression chamber. * **Helium-Oxygen (Heliox):** Used by deep-sea divers to prevent nitrogen narcosis because helium is less soluble and diffuses faster.

Q: Both pale and hemorrhagic infarcts are found in which organ?

Brain. **Explanation:** The nature of an infarct (pale vs. hemorrhagic) is primarily determined by the tissue's vascular supply and density. **Why Brain is the Correct Answer:** The brain is unique because it can exhibit both types of infarcts depending on the mechanism of injury. 1. **Pale (Anemic) Infarcts:** These typically occur due to **thrombotic arterial occlusion** [1]. Since the brain tissue is relatively solid (until liquefactive necrosis sets in), the lack of blood flow results in a pale area of necrosis. 2. **Hemorrhagic (Red) Infarcts:** These occur in the brain following **embolic occlusion** [1]. When an embolus lodges and then fragments or undergoes lysis (reperfusion), blood flows into the previously ischemic, necrotic tissue [1]. Because the brain has a loose texture, blood easily extravasates, turning a pale infarct into a hemorrhagic one. **Analysis of Incorrect Options:** * **Liver:** The liver has a **dual blood supply** (Portal vein and Hepatic artery). While this makes it resistant to infarction, when they do occur, they are typically **hemorrhagic**. * **Heart:** The heart is a solid organ with end-arterial circulation. Myocardial infarctions are almost exclusively **pale**. * **Kidney:** Like the heart, the kidney is a solid organ with a single arterial supply. Renal infarcts are the classic example of **pale, wedge-shaped infarcts**. **High-Yield NEET-PG Pearls:** * **Pale Infarcts:** Occur in solid organs with single venous drainage (Heart, Spleen, Kidney). * **Hemorrhagic Infarcts:** Occur in tissues with dual circulation (Lung, Liver), loose tissues (Bowel, Testis), or following reperfusion [1]. * **Liquefactive Necrosis:** The brain is the only organ where ischemic injury leads to liquefactive necrosis rather than coagulative necrosis [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1266-1269.

Q: Isoprostanes are formed from archidonic acid by which mechanism?

Non-enzymatic free radical peroxidation. **Explanation:** **Isoprostanes** are prostaglandin-like compounds that serve as highly sensitive and specific biomarkers of **oxidative stress**. **1. Why Option D is Correct:** Unlike prostaglandins, which are synthesized via enzymatic pathways, isoprostanes are formed by the **non-enzymatic, free radical-induced peroxidation** of arachidonic acid (and other polyunsaturated fatty acids) while they are still attached to membrane phospholipids. They are subsequently released by phospholipases and can be detected in plasma and urine. Because their formation is independent of enzymes and directly proportional to free radical activity, they are considered the "gold standard" for measuring lipid peroxidation in vivo. **2. Why Other Options are Incorrect:** * **Option A (Cyclooxygenase):** COX-1 and COX-2 enzymes are responsible for the enzymatic conversion of arachidonic acid into prostaglandins (PGE2, PGD2, etc.) and thromboxanes [1]. * **Option B (Lipooxygenase):** LOX enzymes (e.g., 5-LOX) convert arachidonic acid into leukotrienes and lipoxins [1]. * **Option C (Epoxide hydrolase):** This enzyme is involved in the metabolism of epoxides (like EETs) into diols; it is not involved in the primary peroxidation of arachidonic acid. **3. NEET-PG High-Yield Pearls:** * **Biomarker Status:** Isoprostanes (specifically **8-iso-PGF2α**) are the most reliable markers of oxidative stress in diseases like atherosclerosis, diabetes, and Alzheimer’s. * **Vasoactivity:** Unlike some prostaglandins, isoprostanes are potent **vasoconstrictors** (especially in renal and pulmonary vasculature). * **Membrane Damage:** Their formation is a hallmark of **irreversible cell injury** caused by reactive oxygen species (ROS). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 95.

Question 1

A couple is referred to the physician because their first three pregnancies have ended in spontaneous abortion. Chromosomal analysis reveals that the wife has two cell lines in her blood, one with a missing X chromosome (45,X) and the other normal (46,XX). Her chromosomal constitution can be described as?

Accepted Answer

Mosaic

Answer

Chimeric

Answer

Monoploid

Answer

Trisomic

Question 2

Secondary amyloidosis complicates which of the following?

Accepted Answer

Chronic osteomyelitis

Answer

Pneumonia

Answer

Chronic glomerulonephritis

Answer

Osteosarcoma

Question 3

A 12-year-old boy is rescued 2 days after becoming lost in the woods in February. Physical examination shows he has gangrene of his fingers and toes. Which of the following mechanisms of cell injury played the most important role in mediating necrosis in the fingers and toes of this patient?

Accepted Answer

Membrane disruption by water crystals

Answer

Activation of proapoptotic proteins

Answer

Generation of activated oxygen species

Answer

Lipid peroxidation

Question 4

Amyloid (AA) originates from which cell type?

Accepted Answer

Reticulo-endothelial cell

Answer

RBC

Answer

Plasma cell

Answer

Lymphocytes

Question 5

Sudden decrease in atmospheric pressure in deep sea divers resulting in "bends" and "chokes" are features of which condition?

Accepted Answer

Air embolism

Answer

Fat embolism

Answer

Aspiration pneumonia

Answer

Gangrene

Question 6

Both pale and hemorrhagic infarcts are found in which organ?

Accepted Answer

Brain

Answer

Liver

Answer

Heart

Answer

Kidney

Question 7

Caisson's disease is a type of:

Accepted Answer

Gas embolism

Answer

Fat embolism

Answer

Amniotic fluid embolism

Answer

Tumor embolism

Question 8

What is the first cellular change observed in hypoxia?

Accepted Answer

Decreased oxidative phosphorylation in mitochondria

Answer

Cellular swelling

Answer

Alteration in cellular membrane permeability

Answer

Clumping of nuclear chromatin

Question 9

Isoprostanes are formed from archidonic acid by which mechanism?

Accepted Answer

Non-enzymatic free radical peroxidation

Answer

Cyclooxygenase

Answer

Lipooxygenase

Answer

Epoxide hydrolase

Question 10

Mitochondrial abnormality is seen in which of the following conditions?

Accepted Answer

Oncocytoma

Answer

Krabbe's disease

Answer

Fabry disease

Answer

Fanconi syndrome

General Pathology — MCQs

General Pathology — MCQs

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