General Pathology Practice Questions

Q: In Xeroderma Pigmentosum, which DNA repair pathway is defective?

Nucleotide Excision Repair. **Explanation:** **Nucleotide Excision Repair (NER)** is the correct answer because Xeroderma Pigmentosum (XP) is an autosomal recessive disorder characterized by an inherited deficiency in the enzymes required for this specific pathway. NER is responsible for identifying and removing bulky DNA lesions, most notably **pyrimidine dimers** (thymine dimers) caused by exposure to **Ultraviolet (UV) radiation** [1]. When this pathway is defective, DNA damage accumulates, leading to extreme photosensitivity and a 2000-fold increased risk of skin cancers (Basal Cell Carcinoma, Squamous Cell Carcinoma, and Melanoma) [1]. **Analysis of Incorrect Options:** * **Option A (Base Excision Repair):** This pathway repairs non-bulky damage (e.g., deamination or oxidized bases) using glycosylases. It is not the primary defect in XP. * **Option C (Mismatch Repair):** Defects in this pathway (MLH1, MSH2) lead to **Lynch Syndrome** (Hereditary Non-Polyposis Colorectal Cancer) and are characterized by microsatellite instability. * **Option D (Protein Folding):** This refers to proteostasis issues (e.g., Amyloidosis or Prion diseases) and is unrelated to DNA repair mechanisms. **High-Yield Clinical Pearls for NEET-PG:** * **Key Enzyme:** The most common defect involves **UV-specific endonuclease**. * **Clinical Presentation:** "Sunburn on first exposure," severe freckling (lentigines) before age 2, and progressive neurological degeneration in some subtypes (De Sanctis-Cacchione syndrome). * **Associated Cancers:** Early-onset skin cancers and internal malignancies [1]. * **Diagnosis:** Chromosomal breakage studies or unscheduled DNA synthesis (UDS) assays. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 322-323.

Q: Thistle-tube appearance is a characteristic feature of which condition?

Coronal dentin dysplasia. **Explanation:** The **thistle-tube appearance** is a classic radiographic hallmark of **Coronal Dentin Dysplasia (Dentin Dysplasia Type II)**. In this autosomal dominant condition, the primary teeth typically appear opalescent (similar to dentinogenesis imperfecta), but the permanent teeth have a normal clinical color. Radiographically, the pulp chambers of the permanent teeth are abnormally large and elongated, extending apically to resemble a **thistle-tube** or flame shape, often containing multiple pulp stones. **Analysis of Options:** * **Coronal Dentin Dysplasia (Type II):** Characterized by the thistle-tube pulp chamber in permanent teeth and obliterated pulp in primary teeth. * **Radicular Dentin Dysplasia (Type I):** Known as "rootless teeth." Radiographs show short, blunted, or conical roots with total pulp obliteration, resulting in a **half-moon/crescent-shaped** pulp remnant. * **Amelogenesis Imperfecta:** A defect primarily affecting **enamel** formation (ectodermal). Dentin and pulp chambers usually appear normal, though enamel may be thin or absent. * **Dentinogenesis Imperfecta:** Characterized by early, total **obliteration of pulp chambers** and canals in both dentitions, along with "bulbous" crowns and cervical constriction (bell-shaped crowns). **NEET-PG High-Yield Pearls:** * **Dentin Dysplasia Type I:** "Rootless teeth" + Crescent-shaped pulp. * **Dentin Dysplasia Type II:** "Thistle-tube" pulp + Pulp stones. * **Dentinogenesis Imperfecta:** Bulbous crowns + Obliterated pulp + Shell teeth (in Type III). * **Regional Odontodysplasia:** "Ghost teeth" appearance (thin enamel and dentin).

Question 1

In Xeroderma Pigmentosum, which DNA repair pathway is defective?

Accepted Answer

Nucleotide Excision Repair

Answer

Base pair defect

Answer

Mismatch repair defect

Answer

Protein folding

Question 2

What is the pathophysiology of Chronic Granulomatous disease?

Accepted Answer

Decreased oxidative burst

Answer

Defective myeloperoxidase

Answer

Impaired phagocytosis

Answer

Impaired activity of lysozyme

Question 3

A 30-year-old woman suffers a traumatic injury to her breast while playing soccer. Physical examination reveals a 3-cm area of ecchymosis on the left breast. Two weeks later, the patient palpates a firm lump beneath the area where the bruise had been located. Which of the following is the most likely pathologic diagnosis?

Accepted Answer

Fat necrosis

Answer

Duct ectasia

Answer

Fibrocystic change

Answer

Granulomatous mastitis

Question 4

DNA integrity and replication are ensured at which stage of the cell cycle?

Accepted Answer

End of G2

Answer

End of M

Answer

End of G1

Answer

End of S

Question 5

Which of the following findings is not compatible with a diagnosis of juvenile myelomonocytic leukemia?

Accepted Answer

Presence of bcr/abl fusion gene

Answer

Peripheral blood monocytosis, more than 1 x 10^9/L

Answer

Increased hemoglobin F levels for age

Answer

GM-CSF hypersensitivity of myeloid progenitors in vitro

Question 6

Which of the following is NOT a granulomatous disease?

Accepted Answer

Amebiasis

Answer

Leprosy

Answer

Tuberculosis

Answer

Sarcoidosis

Question 7

Which of the following is a characteristic of classical Mendelian inheritance of an autosomal dominant disease?

Accepted Answer

Variable expressivity

Answer

Complete penetrance

Answer

Affected individuals have unaffected parents

Answer

Very early onset in life

Question 8

What is true about Malacetic teeth?

Accepted Answer

All of the above.

Answer

These are soft teeth.

Answer

Softness is due to an increased amount of interglobular dentin.

Answer

This softness leads to increased susceptibility to caries.

Question 9

Thistle-tube appearance is a characteristic feature of which condition?

Accepted Answer

Coronal dentin dysplasia

Answer

Radicular dentin dysplasia

Answer

Amelogenesis imperfecta

Answer

Dentinogenesis imperfecta

Question 10

Which of the following is referred to as the "Governor of Proliferation"?

Accepted Answer

RB

Answer

TP53

Answer

APC

Answer

Patched

General Pathology — MCQs

General Pathology — MCQs

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