General Pathology Practice Questions

Q: Which of the following phospholipids serves as a marker of apoptosis?

Phosphatidylserine. **Explanation:** **Phosphatidylserine (PS)** is the correct answer because of its unique distribution in the cell membrane. In healthy cells, the enzyme **flippase** actively maintains PS on the **inner (cytoplasmic) leaflet** of the plasma membrane. During apoptosis, this asymmetry is lost due to the inactivation of flippase and the activation of **scramblase**. Consequently, PS "flips" to the **outer leaflet** (extracellular surface). This "PS exposure" acts as an "eat-me" signal, recognized by macrophages for phagocytosis without triggering inflammation. Clinical detection of this shift is commonly done using **Annexin V** staining in flow cytometry. **Analysis of Incorrect Options:** * **Phosphatidylinositol (A):** Primarily located on the inner leaflet, it serves as a precursor for second messengers like $IP_3$ and $DAG$ and anchors proteins via GPI linkages. It is not a marker for apoptosis. * **Phosphatidylcholine (C):** The most abundant phospholipid in the eukaryotic membrane, typically found on the outer leaflet. It serves a structural role and is not a signaling marker for cell death. * **Phosphatidylethanolamine (D):** Found mainly in the inner leaflet and involved in membrane fusion and cytokinesis, but its translocation is not the primary diagnostic marker for apoptosis. **High-Yield NEET-PG Pearls:** * **Annexin V:** A protein that binds specifically to Phosphatidylserine in the presence of $Ca^{2+}$; used to identify early apoptotic cells. * **Flippase vs. Scramblase:** Flippase (ATP-dependent) moves PS inward; Scramblase (Ca-activated) moves phospholipids non-specifically in both directions. * **Cardiolipin:** A phospholipid found exclusively in the inner mitochondrial membrane; its oxidation is also linked to the intrinsic pathway of apoptosis.

Q: Familial amyloid polyneuropathy is due to amyloidosis of nerves caused by deposition of which of the following?

Mutant transthyretin. **Explanation:** **Familial Amyloid Polyneuropathy (FAP)**, also known as Transthyretin Amyloidosis (ATTR), is an autosomal dominant multisystem disorder. The correct answer is **Mutant transthyretin (Option C)**. Transthyretin (TTR) is a transport protein synthesized primarily in the liver that carries thyroxine and retinol-binding protein. In FAP, a genetic mutation (most commonly **Val30Met**) causes the TTR protein to become unstable, misfold, and aggregate into insoluble amyloid fibrils. These fibrils deposit preferentially in the peripheral and autonomic nerves, leading to progressive sensorimotor neuropathy and autonomic dysfunction. **Analysis of Incorrect Options:** * **Amyloid associated protein (AA):** This is found in **Secondary Amyloidosis**, typically resulting from chronic inflammatory conditions (e.g., Rheumatoid Arthritis, Osteomyelitis). * **Mutant calcitonin:** This forms amyloid deposits in **Medullary Carcinoma of the Thyroid**. * **Normal transthyretin (Wild-type):** While normal TTR can deposit as amyloid, it causes **Senile Systemic Amyloidosis**, which primarily affects the heart in elderly patients, rather than the hereditary polyneuropathy seen in younger populations. **High-Yield Clinical Pearls for NEET-PG:** * **Most common mutation:** Valine substituted by Methionine at position 30 (Val30Met). * **Primary organ of synthesis:** Liver (This is why liver transplantation was historically a treatment strategy). * **Staining:** Like all amyloids, it shows **Apple-green birefringence** under polarized light with Congo Red stain. * **Newer Treatments:** TTR stabilizers (Tafamidis) and gene-silencing therapies (Patisiran).

Q: Patau syndrome is caused by which chromosomal abnormality?

Trisomy 13. **Explanation:** **Patau syndrome** is a severe genetic disorder caused by **Trisomy 13** (the presence of an extra copy of chromosome 13) [1]. It is the least common and most severe of the three viable autosomal trisomies. The underlying mechanism is usually **meiotic non-disjunction**, most frequently associated with advanced maternal age. **Analysis of Options:** * **Trisomy 13 (Correct):** Characterized by a classic triad of **Microphthalmia, Cleft lip/palate, and Polydactyly** [1]. It also involves severe CNS malformations like holoprosencephaly and scalp defects (aplasia cutis congenita). * **Trisomy 21 (Option A):** This is **Down Syndrome**, the most common autosomal trisomy [1]. Key features include Brushfield spots, Simian crease, and early-onset Alzheimer’s. * **Trisomy 18 (Option B):** This is **Edwards Syndrome** [1]. It is characterized by "rocker-bottom feet," clenched fists with overlapping fingers, and micrognathia. * **18p deletion (Option C):** This refers to Monosomy 18p, a rare chromosomal deletion syndrome distinct from the numerical trisomies. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Trisomies:** **P**atau (Trisomy **13** - **P**uberty age), **E**dwards (Trisomy **18** - **E**lection age), **D**own (Trisomy **21** - **D**rinking age). * **Patau Key Features:** Holoprosencephaly (failure of forebrain to divide), Polydactyly, and "punched-out" scalp lesions (**Aplasia cutis**). * **Screening:** On maternal serum screening, Patau syndrome typically shows **decreased** levels of free β-hCG and PAPP-A in the first trimester. * **Prognosis:** Extremely poor; most infants do not survive beyond the first year of life. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 171-172.

Q: What is the most common site of liquefactive necrosis?

Brain. **Explanation:** **Liquefactive necrosis** is characterized by the transformation of the tissue into a liquid, viscous mass. This occurs due to the digestion of dead cells by hydrolytic enzymes. **Why the Brain is the Correct Answer:** In the Central Nervous System (CNS), ischemic injury (infarct) uniquely results in liquefactive necrosis rather than coagulative necrosis [1]. This is primarily because the brain has a **high lipid content** and **low protein framework**. Additionally, the brain is rich in lysosomal enzymes (hydrolases) and lacks a strong supporting connective tissue stroma. When cells die, these enzymes quickly digest the tissue, and the area is eventually cleared by microglia (macrophages), leaving a cystic cavity. From 10 days to 3 weeks, the tissue liquefies, eventually leaving a fluid-filled cavity [1]. **Why Other Options are Incorrect:** * **Kidney, Liver, and Spleen:** These are solid visceral organs. Ischemic injury (infarct) in these organs typically leads to **Coagulative Necrosis**. In coagulative necrosis, the basic structural outline of the tissue is preserved for several days because the injury denatures not only structural proteins but also the enzymes responsible for proteolysis. **NEET-PG High-Yield Pearls:** 1. **Two Main Scenarios for Liquefactive Necrosis:** * Ischemic injury/Infarction in the **Brain**. * **Abscess formation** (focal bacterial or fungal infections), where inflammatory cells (neutrophils) release potent enzymes that liquefy the surrounding tissue. 2. **Coagulative Necrosis** is the most common pattern of necrosis overall (except in the brain). 3. **Key Histology:** In liquefactive necrosis, the tissue architecture is completely lost [1]; in coagulative necrosis, "tombstone" appearances (preserved outlines without nuclei) are seen. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1268-1269.

Question 1

Which of the following phospholipids serves as a marker of apoptosis?

Accepted Answer

Phosphatidylserine

Answer

Phosphatidylinositol

Answer

Phosphatidylcholine

Answer

Phosphatidylethanolamine

Question 2

Familial amyloid polyneuropathy is due to amyloidosis of nerves caused by deposition of which of the following?

Accepted Answer

Mutant transthyretin

Answer

Amyloid associated protein

Answer

Mutant calcitonin

Answer

Normal transthyretin

Question 3

Patau syndrome is caused by which chromosomal abnormality?

Accepted Answer

Trisomy 13

Answer

Trisomy 21

Answer

Trisomy 18

Answer

18p deletion

Question 4

Congo red staining of abdominal fat has confirmed a diagnosis of Amyloidosis in a 28-year-old man. Which is the most common cause of death in primary AL Amyloidosis?

Accepted Answer

Cardiac failure

Answer

Respiratory failure

Answer

Renal failure

Answer

Septicemia

Question 5

A 56-year-old male patient complains of swelling in his legs. He is a known case of hypertension and is under treatment. On general physical examination, pitting edema is seen on the legs, and his TSH level is 3 mU/L. Which of the following is not a cause of this condition?

Accepted Answer

Myxedema

Answer

Increase in hydrostatic pressure

Answer

Decreased colloid osmotic pressure

Answer

Lymphatic obstruction

Question 6

Which of the following is NOT a form of reversible cellular injury?

Accepted Answer

Karyorrhexis

Answer

Vacuolar degeneration

Answer

Fat accumulation

Answer

Cell swelling

Question 7

Hemosiderin contains which of the following elements?

Accepted Answer

Iron

Answer

Calcium

Answer

Magnesium

Answer

None of the above

Question 8

What is the most common site of liquefactive necrosis?

Accepted Answer

Brain

Answer

Kidney

Answer

Liver

Answer

Spleen

Question 9

Autopsy of a specimen shows pale infarction. Pale infarct is seen in all of the following organs, EXCEPT:

Accepted Answer

Lung

Answer

Heart

Answer

Spleen

Answer

Kidney

Question 10

Frozen section is/are used for all except:

Accepted Answer

Acid-fast bacilli staining

Answer

Enzyme studies

Answer

Intraoperative histopathological examination

Answer

Fat staining

General Pathology — MCQs

General Pathology — MCQs

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