Infectious Diseases Practice Questions

Q: What is the characteristic appearance of Cowdry type A inclusion bodies?

Granular. **Explanation:** **Cowdry type A inclusion bodies** are characteristic intranuclear inclusions most commonly associated with **Herpes Simplex Virus (HSV)** and **Varicella-Zoster Virus (VZV)** [1]. 1. **Why Option A is Correct:** Cowdry type A inclusions are described as large, single, eosinophilic (pinkish), and **granular** masses. They are typically surrounded by a clear "halo" (due to the margination of chromatin against the nuclear membrane), giving the nucleus an "owl-eye" appearance [1]. The granular texture represents the site of active viral replication and protein assembly within the nucleus. 2. **Why Other Options are Incorrect:** * **Option B (Circumscribed):** While they are distinct, "granular" is the more specific pathological descriptor for Type A. "Circumscribed" is often used to describe Cowdry Type B inclusions (found in Polio or Adenovirus), which are smaller and multiple. * **Option C (Polio virus):** Poliovirus typically produces **Cowdry type B** inclusion bodies, which are smaller, multiple, and do not show the same degree of chromatin margination seen in Type A. **High-Yield NEET-PG Pearls:** * **Cowdry Type A:** Associated with HSV, VZV, and Yellow Fever (Torres bodies) [1]. * **Cowdry Type B:** Associated with Poliovirus and Adenovirus. * **Tzanck Smear:** A rapid bedside test for Herpes where you look for multinucleated giant cells containing these Cowdry Type A inclusions [1]. * **Negri Bodies:** Eosinophilic *intracytoplasmic* inclusions pathognomonic for Rabies (found in Purkinje cells of the cerebellum and pyramidal cells of the hippocampus). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 366-367.

Q: What are the characteristic findings on a liver biopsy in a patient with malaria?

Kupffer cell hyperplasia. **Explanation:** In malaria, the liver is involved during the **exo-erythrocytic phase** (pre-erythrocytic schizogony). The characteristic finding on liver biopsy is **Kupffer cell hyperplasia** [1]. These resident macrophages become enlarged and hyperplastic as they actively phagocytose malarial pigment (**hemozoin**), cellular debris, and parasitized erythrocytes [1]. The liver often appears slate-grey or dark brown macroscopically due to this pigment deposition [1]. **Analysis of Options:** * **Kupffer cell hyperplasia (Correct):** This is a reactive change to the systemic parasitemia and the release of metabolic byproducts of *Plasmodium* species [1]. * **Microabscesses:** These are typical of pyogenic liver abscesses (e.g., *E. coli*, *Klebsiella*) or fungal infections (Candidiasis), not protozoal infections like malaria. * **Piecemeal necrosis (Interface Hepatitis):** This is the hallmark of **Chronic Autoimmune Hepatitis** or Chronic Viral Hepatitis (B and C), characterized by inflammation extending beyond the limiting plate. * **Non-caseating granuloma:** This is characteristic of **Sarcoidosis**, Berylliosis, or certain drug reactions. While some infections (like Leprosy or Brucellosis) cause them, malaria does not. **NEET-PG High-Yield Pearls:** * **Hemozoin:** An iron-containing pigment (hematin) produced by the parasite from the digestion of host hemoglobin [1]. It is birefringent under polarized light [1]. * **Durck’s Granulomas:** Small foci of white matter necrosis and microglial reaction seen in **Cerebral Malaria**. * **Blackwater Fever:** Severe hemolysis leading to hemoglobinuria and acute renal failure, typically associated with *P. falciparum*. * **Hypnozoites:** Latent stages in the liver responsible for relapses in *P. vivax* and *P. ovale*. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 398-400.

Q: A radical group commissions scientists to develop a Category A bioterrorism agent. They want an agent that will paralyze victims within hours and be disguised within innocuous-appearing cans of split pea soup. Which of the following organisms best meets the requirements stated?

Clostridium botulinum. **Explanation:** The correct answer is **Clostridium botulinum**. This question tests the integration of microbiology, public health (bioterrorism categories), and clinical presentation. **Why Clostridium botulinum is correct:** * **Category A Agent:** The CDC classifies *C. botulinum* toxin as a Category A bioterrorism agent because it is highly lethal, easy to disseminate, and requires special action for public health preparedness. * **Mechanism of Action:** It produces a potent neurotoxin that inhibits the release of **Acetylcholine (ACh)** at the neuromuscular junction by cleaving SNARE proteins. This leads to a rapid-onset, **symmetric descending flaccid paralysis**. * **Transmission:** In a bioterrorism context, it can be delivered via aerosol or contaminated food. It is classically associated with **improperly canned alkaline foods** (like split pea soup), where the anaerobic environment allows the spores to germinate and produce toxin. **Why other options are incorrect:** * **Chlamydia psittaci:** Causes Psittacosis (atypical pneumonia). It is a Category B agent and does not cause paralysis. * **Ebola virus:** While a Category A agent, it causes hemorrhagic fever, not rapid paralysis, and is not typically spread via canned food. * **Hantavirus:** Causes Hantavirus Pulmonary Syndrome (HPS) or Hemorrhagic Fever with Renal Syndrome (HFRS). It is transmitted via rodent excreta, not canned food. **NEET-PG High-Yield Pearls:** * **Clinical Triad:** Afebrile, symmetric descending paralysis, and clear sensorium. * **Early Signs:** The "4 Ds" – Diplopia, Dysarthria, Dysphagia, and Dyspnea. * **Infant Botulism:** Associated with **honey** ingestion (ingestion of spores, unlike adult botulism which is usually ingestion of pre-formed toxin). * **Diagnosis:** Confirmed by demonstrating toxin in serum, stool, or suspected food via mouse bioassay.

Question 1

What is the histopathological finding in the liver in cases of malaria?

Accepted Answer

Kupffer's cell hyperplasia with macrophage infiltration around periportal area laden with pigments

Answer

Microabscess formation

Answer

Non-caseating granuloma

Answer

Non-specific finding of neutrophilic infiltration

Question 2

HPV-16/18 is detected in which of the following conditions?

Accepted Answer

All of the above

Answer

Condylomas

Answer

Squamous Cell papilloma

Answer

Focal epithelial hyperplasia

Question 3

What does a prion include?

Accepted Answer

Proteins

Answer

DNA and RNA

Answer

Only RNA

Answer

Only DNA

Question 4

What is the characteristic appearance of Cowdry type A inclusion bodies?

Accepted Answer

Granular

Answer

Circumscribed

Answer

Found in polio virus infections

Answer

None of the above

Question 5

A 62-year-old patient presents with hematuria. Investigations reveal renal calculi, calcifications in the wall of the urinary bladder, and a small contracted bladder. What is the most likely cause?

Accepted Answer

Schistosomiasis

Answer

Prostate calculi

Answer

Carcinoma of the bladder

Answer

Bladder diverticulitis

Question 6

What are the characteristic findings on a liver biopsy in a patient with malaria?

Accepted Answer

Kupffer cell hyperplasia

Answer

Microabscesses

Answer

Piecemeal necrosis

Answer

Non-caseating granuloma

Question 7

Zenker's degeneration of the abdominal musculature is seen in which of the following conditions?

Accepted Answer

Typhoid

Answer

Cholera

Answer

Myotonia congenita

Answer

Amyloidosis

Question 8

A 6-year-old girl presents with a blotchy, reddish-brown rash on her face, trunk, and proximal extremities that developed over 3 days. Physical examination reveals 0.2-cm to 0.5-cm ulcerated lesions on the oral mucosa and generalized tender lymphadenopathy. A cough with minimal sputum production worsens over the next 3 days. Which of the following viruses is most likely to produce these findings?

Accepted Answer

Rubeola virus

Answer

Epstein-Barr virus

Answer

Mumps virus

Answer

Rubella virus

Question 9

A radical group commissions scientists to develop a Category A bioterrorism agent. They want an agent that will paralyze victims within hours and be disguised within innocuous-appearing cans of split pea soup. Which of the following organisms best meets the requirements stated?

Accepted Answer

Clostridium botulinum

Answer

Chlamydia psittaci

Answer

Ebola virus

Answer

Hantavirus

Question 10

A 20-year-old man who has multiple sexual partners and does not use barrier precautions has had a non-tender ulcer on his penis for the past week. On physical examination, the 0.6-cm lesion has a firm, erythematous base and sharply demarcated borders. The lesion is scraped, and the microscopic darkfield examination is positive for motile spirochetes. Which of the following inflammatory processes is most likely to accompany this infection?

Accepted Answer

Perivascular inflammation with plasma cells

Answer

Acute inflammation with abscess formation

Answer

Granulomatous inflammation with caseation

Answer

Gummatous inflammation with necrosis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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