General Pathology Practice Questions

Q: Which stain is used for melanin?

Masson Fontana. **Explanation:** **Masson Fontana (Option A)** is the correct answer. It is an **argentaffin stain**, meaning melanin has the inherent ability to reduce silver nitrate to metallic silver without the need for an external reducing agent. This results in melanin granules appearing black against a pink/red background. It is the gold standard histochemical stain for identifying melanin in conditions like malignant melanoma or to distinguish it from other brown pigments. **Analysis of Incorrect Options:** * **Prussian Blue (Option B):** This is used to detect **Ferric iron (Hemosiderin)**. It is a classic stain used in cases of hemochromatosis or to identify "heart failure cells" (siderophages) in the lungs. * **Masson Trichrome (Option C):** This is a connective tissue stain used to differentiate **collagen (blue/green)** from smooth muscle and epithelium (red). It is frequently used to assess the degree of fibrosis in liver cirrhosis or chronic kidney disease. * **Congo Red (Option D):** This is the specific stain for **Amyloid** [1]. Under polarized light, amyloid stained with Congo red exhibits a characteristic **apple-green birefringence** [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Melanin Bleaching:** If a lesion is heavily pigmented, "bleaching" with hydrogen peroxide or potassium permanganate is done to see nuclear details. * **DOPA Reaction:** This is an enzyme histochemical method used to identify melanocytes by detecting tyrosinase activity. * **IHC Markers:** For malignant melanoma, **S-100** (sensitive), **HMB-45** (specific), and **Melan-A** are the high-yield immunohistochemical markers. * **Other Silver Stains:** Do not confuse Masson Fontana with **Von Kossa** (used for Calcium) or **Reticulin stain** (used for Type III Collagen). **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.

Q: Deficiency of which enzyme causes Tay-Sachs disease?

Hexosaminidase A. **Explanation:** **Tay-Sachs Disease** is an autosomal recessive lysosomal storage disorder belonging to the group of **GM2 gangliosidoses**. It is caused by a deficiency of the enzyme **Hexosaminidase A**, which leads to the toxic accumulation of GM2 gangliosides, primarily within the neurons of the central nervous system. * **Why Option A is correct:** Hexosaminidase A (composed of $\alpha$ and $\beta$ subunits) requires an activator protein to degrade GM2 ganglioside. A mutation in the *HEXA* gene on chromosome 15 leads to enzyme deficiency, resulting in progressive neurodegeneration and the characteristic "cherry-red spot" on the macula [1]. * **Why incorrect options are wrong:** * **B. Alpha-L-iduronidase:** Deficiency causes **Hurler Syndrome** (Mucopolysaccharidosis I) [2], characterized by corneal clouding and hepatosplenomegaly. * **C. Alpha-galactosidase A:** Deficiency causes **Fabry Disease**, an X-linked disorder presenting with angiokeratomas, peripheral neuropathy, and renal failure. * **D. Acid alpha-glucosidase (Acid Maltase):** Deficiency causes **Pompe Disease** (Glycogen Storage Disease Type II), leading to massive cardiomegaly and muscular hypotonia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Morphology:** Histology shows "onion-skin" appearance of lysosomes (whorled configurations) [1]. 2. **Clinical Triad:** Progressive neurodegeneration, developmental delay, and **Cherry-red spot** on the macula [1]. 3. **Key Distinction:** Unlike Gaucher or Niemann-Pick disease, Tay-Sachs has **NO hepatosplenomegaly**. 4. **Epidemiology:** High prevalence in the Ashkenazi Jewish population. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 161. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 163-164.

Q: Which stain is characteristically used for the diagnosis of amyloidosis?

Congo red. **Explanation:** **Congo Red** is the gold standard and most characteristic stain for diagnosing amyloidosis [1]. Amyloid is a pathologic proteinaceous substance deposited in the extracellular space. When stained with Congo Red and viewed under **polarized light**, it exhibits a pathognomonic **apple-green birefringence** [1]. This occurs because the dye molecules align parallel to the highly organized cross-beta-pleated sheet structure of the amyloid fibrils [1]. **Analysis of Options:** * **B. Thioflavin T:** While this fluorescent dye binds to amyloid and is highly sensitive, it is **not specific**. It is often used for screening in research settings but is not the "characteristic" diagnostic stain used in routine clinical pathology compared to Congo Red. * **C. Reticulin stain:** This is a silver-based stain used to visualize Type III collagen fibers (reticulin). It is used to evaluate liver architecture or bone marrow fibrosis, not amyloid. * **D. Gram’s iodine:** Historically, Virchow used iodine to identify amyloid (hence the name "amyloid" or starch-like), which turns the deposits mahogany brown. However, this is a gross macroscopic test and is no longer used for definitive microscopic diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **H&E Appearance:** Amyloid appears as an extracellular, amorphous, eosinophilic (pink) hyaline material [1]. * **Most Common Type:** Systemic AL (Light chain) amyloidosis is associated with plasma cell dyscrasias [1]. * **Biopsy Site:** The most common site for screening systemic amyloidosis is **Abdominal Fat Pad aspiration** or Rectal biopsy. * **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. 268-269.

Q: Paternal 15 chromosome deletion is seen in which of the following conditions?

Prader Willi syndrome. This question tests the concept of **Genomic Imprinting**, an epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner [1]. ### **Explanation of the Correct Answer** **Prader-Willi Syndrome (PWS)** occurs due to the loss of function of genes in the **15q11-q13** region on the **paternal chromosome** [1]. In normal individuals, the maternal copy of these specific genes is silenced (imprinted), so the individual relies solely on the paternal copy. If the paternal segment is deleted (70% of cases) or if there is Maternal Uniparental Disomy (25%), no functional genes remain, leading to the syndrome. * **Clinical Presentation:** Neonatal hypotonia, hyperphagia leading to morbid obesity, hypogonadism, and small hands/feet. ### **Analysis of Incorrect Options** * **A. Angelman Syndrome:** This is the "sister" condition to PWS. It involves a deletion of the same region (15q11-q13) but on the **maternal chromosome** [1]. It results in the "Happy Puppet" profile: inappropriate laughter, ataxia, and seizures [1]. * **C. Down Syndrome:** Caused by **Trisomy 21**. It is a numerical chromosomal aberration, not related to imprinting or chromosome 15. * **D. Turner Syndrome:** Caused by **Monosomy X (45, XO)**. It is characterized by short stature, webbed neck, and streak ovaries. ### **High-Yield Clinical Pearls for NEET-PG** * **Mnemonic:** **P**ader-Willi = **P**aternal deletion; **A**ngelman = **M**aternal deletion (**MAP**: Maternal Angelman Prader). * **Uniparental Disomy (UPD):** PWS can also be caused by inheriting two copies of chromosome 15 from the mother (Maternal UPD) and none from the father. * **Diagnosis:** The gold standard screening test for both syndromes is **DNA Methylation Analysis** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 181-183.

Question 1

CD95 is a marker of which of the following?

Accepted Answer

Extrinsic pathway of apoptosis

Answer

Intrinsic pathway of apoptosis

Answer

Monocyte

Answer

Leucocyte

Question 2

Which stain is used for melanin?

Accepted Answer

Masson Fontana

Answer

Prussian blue

Answer

Masson trichrome

Answer

Congo red

Question 3

What is the most common cause of death in primary amyloidosis?

Accepted Answer

Cardiac failure

Answer

Respiratory failure

Answer

Renal failure

Answer

Septicemia

Question 4

Deficiency of which enzyme causes Tay-Sachs disease?

Accepted Answer

Hexosaminidase A

Answer

Alpha-L-iduronidase

Answer

Alpha-galactosidase A

Answer

Acid alpha-glucosidase

Question 5

Which of the following conditions does not typically progress to carcinoma?

Accepted Answer

Bowenoid papulosis

Answer

Bowen's disease

Answer

Leukoplakia

Answer

Erythroplakia

Question 6

Which stain is characteristically used for the diagnosis of amyloidosis?

Accepted Answer

Congo red

Answer

Thioflavin T

Answer

Reticulin stain

Answer

Gram's iodine

Question 7

Fibrin is degraded by which of the following?

Accepted Answer

Plasmin

Answer

Plasminogen

Answer

Thromboplastin

Answer

Fibrin degradation products

Question 8

Which of the following is a pathological calcification?

Accepted Answer

Suprasellar calcification

Answer

Basal ganglia calcification

Answer

Pineal body calcification

Answer

Choroid calcification

Question 9

In an Autosomal Recessive (AR) disorder, if one parent is normal and the other is a carrier, and the child is affected, what is the most likely explanation for this inheritance pattern?

Accepted Answer

Uniparental disomy

Answer

Germline mosaicism

Answer

Genomic imprinting

Answer

Mitochondrial inheritance

Question 10

Paternal 15 chromosome deletion is seen in which of the following conditions?

Accepted Answer

Prader Willi syndrome

Answer

Angelman syndrome

Answer

Down syndrome

Answer

Turner syndrome

General Pathology — MCQs

General Pathology — MCQs

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