Infectious Diseases Practice Questions

Q: A 6-year-old girl presents with intense perianal itching, especially at night. Physical examination reveals perianal excoriation. An adhesive tape test is positive for worms. Which of the following is the most likely parasite in this patient?

Enterobius vermicularis. **Explanation** The clinical presentation described is a classic case of **Enterobiasis**, caused by **Enterobius vermicularis** (Pinworm or Seatworm). **Why Option C is Correct:** * **Nocturnal Pruritus Ani:** The hallmark symptom is intense perianal itching at night. This occurs because the gravid female worm migrates out of the anus to deposit eggs on the perianal skin folds. * **Adhesive Tape Test (Scotch Tape Test):** This is the gold standard for diagnosis. Since eggs are rarely found in feces, a transparent adhesive tape is applied to the perianal area in the morning to collect and visualize the characteristic **planoconvex (D-shaped)** eggs under a microscope. * **Transmission:** It is common in children due to the feco-oral route and autoinoculation (finger-to-mouth after scratching). **Why Other Options are Incorrect:** * **Options A & D (Hookworms):** *Ancylostoma duodenale* and *Necator americanus* primarily cause iron-deficiency anemia and ground itch at the site of larval penetration (usually the feet). They do not cause perianal itching. * **Option B (Ascaris lumbricoides):** The giant roundworm typically presents with intestinal obstruction, Loeffler’s syndrome (pulmonary phase), or biliary colic. Diagnosis is made by finding eggs in the stool, not via the tape test. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Eggs are non-bile stained and D-shaped. * **Treatment:** **Albendazole** or Mebendazole (single dose, repeated after 2 weeks). It is crucial to **treat the entire family** to prevent reinfection. * **Ectopic Migration:** In females, the worm can migrate into the vagina, leading to vulvovaginitis or pelvic inflammatory disease (PID).

Q: "Torres bodies" are seen in which condition?

Yellow fever. **Explanation:** **Yellow Fever** is the correct answer. It is a viral hemorrhagic fever caused by a Flavivirus, characterized by significant hepatic involvement. The hallmark histopathological finding in the liver is **Councilman bodies** (apoptotic hepatocytes) [1]. When these eosinophilic, acidophilic inclusion bodies are specifically found within the nuclei of hepatocytes in Yellow Fever, they are referred to as **Torres bodies**. These represent areas of focal hyaline necrosis and are a classic high-yield morphologic marker for this disease. **Analysis of Incorrect Options:** * **Kala Azar (Visceral Leishmaniasis):** Characterized by **LD bodies** (Leishman-Donovan bodies), which are amastigote forms of the parasite found within macrophages of the reticuloendothelial system. * **Q-fever:** Caused by *Coxiella burnetii*. The characteristic histopathological finding is the **"Doughnut granuloma"** (a fibrin-ring granuloma with a central lipid vacuole), typically seen in the liver or bone marrow. * **Lymphogranuloma venereum (LGV):** Caused by *Chlamydia trachomatis* (serotypes L1-L3). It is associated with **"Stellate abscesses"** (star-shaped areas of necrosis) within the inguinal lymph nodes. **NEET-PG Clinical Pearls:** * **Councilman bodies** are seen in Yellow Fever and other forms of viral hepatitis, but **Torres bodies** are specific to Yellow Fever [1]. * Yellow Fever liver pathology typically shows **mid-zonal necrosis** (Zone 2 of the hepatic acinus), sparing the cells around the central vein and portal tract. * Other important bodies to remember: **Negri bodies** (Rabies), **Guarnieri bodies** (Smallpox), and **Henderson-Peterson bodies** (Molluscum contagiosum). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 386-387.

Q: Which of the following viruses appears to be involved in the pathogenesis of Kaposi's sarcoma?

Human Herpes Virus 8. ### Explanation **Correct Answer: C. Human Herpes Virus 8 (HHV-8)** **Pathogenesis:** Kaposi’s Sarcoma (KS) is a vascular neoplasm caused by **Human Herpes Virus 8 (HHV-8)**, also known as **Kaposi Sarcoma-associated Herpesvirus (KSHV)** [1]. HHV-8 infects vascular and lymphatic endothelial cells. The virus carries genes that mimic host cellular genes (like v-cyclin and v-IL6), which promote cell proliferation, inhibit apoptosis, and induce angiogenesis (via VEGF). It is most commonly seen in the context of HIV/AIDS (Epidemic KS), but also occurs in elderly Mediterranean men (Classic KS), organ transplant recipients (Iatrogenic KS), and endemic regions of Africa [1]. **Analysis of Incorrect Options:** * **A. Human Herpes Virus 3 (Varicella-Zoster Virus):** Causes chickenpox (primary infection) and shingles (reactivation). It is not oncogenic. * **B. Human Herpes Virus 1 (Herpes Simplex Virus-1):** Primarily causes orolabial herpes (cold sores) and sporadic encephalitis. * **D. Human Herpes Virus 4 (Epstein-Barr Virus):** While EBV is oncogenic, it is associated with Burkitt lymphoma, Nasopharyngeal carcinoma, and Hodgkin lymphoma, but not Kaposi’s sarcoma [1]. **High-Yield NEET-PG Pearls:** * **Histology:** Look for **spindle-shaped cells**, slit-like vascular spaces, and extravasated RBCs with hemosiderin-laden macrophages. * **Marker:** **LANA-1** (Latency-Associated Nuclear Antigen) is a highly specific immunohistochemical marker for HHV-8 in tissue sections. * **Clinical Presentation:** Characterized by purple, red, or brown skin plaques or nodules, often involving the lower extremities, mucous membranes, or viscera [1]. * **Association:** HHV-8 is also implicated in **Primary Effusion Lymphoma (PEL)** and **Multicentric Castleman Disease**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 261-262.

Question 1

What is the most common malignancy in patients with AIDS?

Accepted Answer

Kaposi sarcoma

Answer

B cell lymphoma

Answer

Leukemia of myeloid origin

Answer

Burkitt's lymphoma

Question 2

Glomus cells are found in which of the following?

Accepted Answer

Carotid body tumor

Answer

Thyroid carcinoma

Answer

Liver carcinoma

Answer

None of the above

Question 3

A 45-year-old man presents with chest pain, fever, productive cough, and rust-colored sputum. He had a history of tuberculosis in his early 20s. A chest X-ray shows multiple, nodular infiltrates and cavitary lesions. A lung biopsy reveals necrotizing inflammation and vascular thrombi with branching fungal hyphae. Which of the following is the most likely diagnosis?

Accepted Answer

Aspergillosis

Answer

Actinomycosis

Answer

Candidiasis

Answer

Cryptococcosis

Question 4

Cold abscess formation is due to?

Accepted Answer

Formation of caseous pus without signs of acute inflammation

Answer

Presence of acute inflammation

Answer

Formation of caseous pus with signs of acute inflammation

Answer

Infected cyst

Question 5

Caseating granuloma is commonly seen in which of the following conditions?

Accepted Answer

Tuberculosis

Answer

Viral infections

Answer

Typhoid

Answer

Amoebiasis

Question 6

A 6-year-old girl presents with intense perianal itching, especially at night. Physical examination reveals perianal excoriation. An adhesive tape test is positive for worms. Which of the following is the most likely parasite in this patient?

Accepted Answer

Enterobius vermicularis

Answer

Ancylostoma duodenale

Answer

Ascaris lumbricoides

Answer

Necator americanus

Question 7

Necrotizing granulomatous inguinal lymphadenopathy is caused by which of the following?

Accepted Answer

Syphilis

Answer

Granuloma inguinale

Answer

Sarcoidosis

Answer

Tuberculosis

Question 8

"Torres bodies" are seen in which condition?

Accepted Answer

Yellow fever

Answer

Kala Azar

Answer

Q-fever

Answer

Lymphogranuloma venereum (LGV)

Question 9

Which of the following viruses appears to be involved in the pathogenesis of Kaposi's sarcoma?

Accepted Answer

Human Herpes Virus 8

Answer

Human Herpes Virus 3

Answer

Human Herpes Virus 1

Answer

Human Herpes Virus 4

Question 10

In primary tuberculosis, all of the following may be seen except?

Accepted Answer

Cavitation

Answer

Caseation

Answer

Calcification

Answer

Langhans giant cell

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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