General Pathology Practice Questions

Q: The primary defect in Xeroderma pigmentosa is:

Formation of thymidine dimers. **Explanation:** **Xeroderma Pigmentosum (XP)** is an autosomal recessive genetic disorder characterized by an extreme sensitivity to ultraviolet (UV) radiation. [1] **1. Why Option A is Correct:** The primary event in XP is the **formation of pyrimidine dimers (specifically thymidine dimers)** in DNA when skin is exposed to UV light [1]. In healthy individuals, these dimers are repaired via the **Nucleotide Excision Repair (NER)** pathway. In XP patients, there is a deficiency in the enzymes required for this pathway (most commonly **UV-specific endonucleases**). The inability to repair these dimers leads to accumulated mutations, resulting in skin cancers at a very young age [1]. **2. Why Incorrect Options are Wrong:** * **Option B:** Poly ADP ribose polymerase (PARP) is involved in Base Excision Repair (BER) and detecting single-strand breaks. It is not the primary defect in XP. * **Option C:** While a defect in the repair pathway exists, the *primary defect* or initiating event mentioned in the context of the question's pathology is the **formation of the dimers** themselves which the body fails to excise. (Note: If the question asked for the defective *enzyme*, endonuclease would be the answer). * **Option D:** UV radiation specifically causes the linkage of adjacent pyrimidines (Thymine/Cytosine), not purines like Adenine [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Recessive. * **Clinical Triad:** Photophobia, severe sunburn/erythema, and early-onset skin cancers (Basal Cell Carcinoma, Squamous Cell Carcinoma, and Melanoma). * **Key Enzyme Deficit:** UV-specific endonuclease (NER pathway). * **Associated Condition:** Cockayne Syndrome also involves NER defects but presents with "Mickey Mouse" facies and dwarfism without increased cancer risk. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 322-323.

Q: Ehlers-Danlos syndrome is due to a defect in which of the following?

Collagen. **Explanation:** **Ehlers-Danlos Syndrome (EDS)** is a clinically and genetically heterogeneous group of disorders characterized by a defect in the synthesis or structure of **fibrillar collagen** [1]. Collagen provides the necessary tensile strength to connective tissues; hence, its deficiency leads to the hallmark triad of **skin hyperextensibility, joint hypermobility, and tissue fragility** [1]. * **Why Collagen is Correct:** EDS results from mutations in genes encoding structural proteins (like Type I, III, or V collagen) or enzymes responsible for post-translational modifications (like lysyl hydroxylase) [1]. For example, the **Classical type** is associated with Type V collagen (COL5A1/A2), while the **Vascular type** involves Type III collagen (COL3A1). * **Why Incorrect Options are Wrong:** * **Elastin:** Defects in elastin or its scaffold protein, Fibrillin-1, lead to **Marfan Syndrome** or Cutis Laxa, not EDS. * **Keratin:** Mutations in keratin filaments primarily affect the epidermis, leading to disorders like **Epidermolysis Bullosa Simplex** or Ichthyosis. * **Laminin:** Laminins are major components of the basal lamina. Defects here are associated with certain types of **Junctional Epidermolysis Bullosa** and Muscular Dystrophy. **High-Yield Clinical Pearls for NEET-PG:** * **Vascular Type (Type IV):** Most serious form; involves Type III collagen. Risk of spontaneous rupture of large arteries or the colon [1]. * **Kyphoscoliotic Type:** Due to deficiency of **Lysyl Hydroxylase**; characterized by hypotonia and ocular fragility. * **Beighton Score:** Used clinically to assess the degree of joint hypermobility. * **Wound Healing:** Patients often exhibit "cigarette paper" or "papyraceous" scarring due to poor collagen cross-linking [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 154-156.

Q: Tumor marker CA 15-3 is associated with which type of cancer?

Breast cancer. **Explanation:** **CA 15-3 (Cancer Antigen 15-3)** is a tumor marker primarily used in the clinical management of **Breast Cancer**. It is a product of the *MUC1* gene and is a high-molecular-weight glycoprotein found on the luminal surface of glandular epithelium. In malignant breast cells, this protein is overexpressed and shed into the bloodstream. While not used for screening due to low sensitivity in early stages, it is highly valuable for monitoring treatment response and detecting recurrence in patients with metastatic breast cancer. **Analysis of Incorrect Options:** * **Ovarian Cancer:** The primary tumor marker is **CA-125**. While CA 15-3 can occasionally be elevated in ovarian malignancy, it is not the diagnostic or monitoring standard. * **Prostate Cancer:** The gold standard marker is **PSA (Prostate-Specific Antigen)**. Acid phosphatase is another historical marker associated with this cancer. * **Renal Cancer:** There are no highly specific serum tumor markers for Renal Cell Carcinoma (RCC), though LDH or erythropoietin may sometimes be elevated. **High-Yield Clinical Pearls for NEET-PG:** * **CA 15-3 and CA 27-29:** Both are markers for breast cancer monitoring. * **CA 19-9:** Associated with Pancreatic and Cholangiocarcinoma. * **CA 125:** Associated with Serous Ovarian Cystadenocarcinoma. * **AFP (Alpha-fetoprotein):** Associated with Hepatocellular Carcinoma (HCC) and Yolk Sac Tumors. * **CEA (Carcinoembryonic Antigen):** Primarily used for Colorectal Cancer.

Question 1

In myocardial infarction, fibrosis is typically seen after how many days?

Accepted Answer

5 days

Answer

2 days

Answer

1 week

Answer

3 weeks

Question 2

The primary defect in Xeroderma pigmentosa is:

Accepted Answer

Formation of thymidine dimers

Answer

Poly ADP ribose polymerase is defective

Answer

Exonuclease is defective

Answer

Formation of adenine dimers

Question 3

What is the cause for caseous necrosis in Tuberculosis?

Accepted Answer

High lipid content

Answer

Hydrolytic enzymes

Answer

Mycolic acid

Answer

Hydrophobic changes by the bacterial wall

Question 4

Epigenetics deals with genetic modifications that do not alter the sequence of DNA. Which of the following methods cannot detect epigenetic modifications?

Accepted Answer

High-performance liquid chromatography (HPLC)

Answer

ChIP-on-chip

Answer

Bisulphite sequencing

Answer

Methylation-specific PCR

Question 5

Xerostomia and enlargement of salivary and lacrimal glands are seen in which condition?

Accepted Answer

Mickulicz disease

Answer

Sicca syndrome

Answer

Sjogren syndrome

Answer

None of the above

Question 6

Senile cardiac amyloidosis is associated with which protein?

Accepted Answer

Transthyretin

Answer

Atrial Natriuretic Peptide (ANP)

Answer

Beta 2 microglobulin

Answer

Gelsolin

Question 7

All of the following are true for exudates, except?

Accepted Answer

It has a low fibrin content

Answer

It has a specific gravity of 1.018

Answer

It has more than 3% proteins

Answer

It is mucinous in consistency

Question 8

Ehlers-Danlos syndrome is due to a defect in which of the following?

Accepted Answer

Collagen

Answer

Elastin

Answer

Keratin

Answer

Laminin

Question 9

Tumor marker CA 15-3 is associated with which type of cancer?

Accepted Answer

Breast cancer

Answer

Ovarian cancer

Answer

Prostate cancer

Answer

Renal cancer

Question 10

In apoptosis, permeabilization of which membrane occurs?

Accepted Answer

Mitochondrial membrane

Answer

Nuclear membrane

Answer

Cytoplasmic membrane

Answer

Lysosome

General Pathology — MCQs

General Pathology — MCQs

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