Infectious Diseases Practice Questions

Q: A 45-year-old HIV-positive male presented with dysphagia. Endoscopy and biopsy were performed. What is the most likely diagnosis based on the endoscopic and histological findings?

Cytomegalovirus (CMV) esophagitis. ***Cytomegalovirus (CMV) esophagitis*** - Characterized by **large linear ulcerations** on endoscopy, typically seen in severely immunocompromised HIV patients with **CD4+ count <50 cells/μL**. - Histologically shows pathognomonic **owl-eye nuclear inclusions** (large eosinophilic intranuclear inclusions with surrounding halo) in infected cells. *Herpes esophagitis* - Endoscopically presents with **small, punched-out ulcers** rather than large linear ulcerations seen in CMV. - Histologically shows **multinucleated giant cells** with **Cowdry A inclusions**, not the characteristic owl-eye inclusions of CMV. *Candida esophagitis* - Endoscopically appears as **white plaques** or **pseudomembranes** that can be wiped off, revealing erythematous mucosa underneath. - Histologically shows **pseudohyphae and budding yeasts** on PAS or GMS staining, without the viral inclusions described. *Pseudomonas esophagitis* - Extremely rare cause of esophagitis, typically occurring only in **severely neutropenic patients** or those with extensive burns. - Would show **gram-negative rod bacteria** on histology and **necrotizing inflammation**, not the viral cytopathic effects described.

Q: What is the multifocal tumor of vascular origin commonly seen in a patient with AIDS?

Kaposi sarcoma. **Kaposi Sarcoma (KS)** is the correct answer because it is a low-grade vascular tumor strongly associated with **Human Herpesvirus 8 (HHV-8)** and is the most common neoplasm seen in patients with AIDS [1]. It typically presents as multifocal, purplish-red cutaneous nodules or plaques but can also involve visceral organs like the lungs and GI tract [2]. Pathologically, it is characterized by the proliferation of spindle cells, slit-like vascular spaces, and extravasated red blood cells [2]. **Analysis of Incorrect Options:** * **Astrocytoma:** While brain tumors occur in immunocompromised states, astrocytomas are not specifically associated with AIDS or vascular origin. * **Gastric Carcinoma:** Though AIDS patients have a higher risk of certain GI malignancies, gastric adenocarcinoma is not a vascular tumor and is primarily linked to *H. pylori* or genetic factors. * **Primary CNS Lymphoma:** This is the second most common malignancy in AIDS patients (after KS). However, it is a **B-cell neoplasm** associated with **EBV**, not a tumor of vascular origin [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Defining Characteristic:** KS is an **AIDS-defining illness**. * **Histology:** Look for "spindle cells" and "slit-like spaces" containing RBCs [2]. * **Four Clinical Variants:** Classic (European), Endemic (African), Transplant-associated (Immunosuppression), and Epidemic (AIDS-associated). * **Treatment:** Highly Active Antiretroviral Therapy (HAART) often leads to the regression of AIDS-related KS lesions [3]. **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. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 526-527. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 260-261.

Q: Which of the following statements is NOT TRUE regarding primary Herpes Simplex Virus (HSV) infections?

Occurs epidemically.. **Explanation:** The correct answer is **C (Occurs epidemically)** because Herpes Simplex Virus type 1 (HSV-1) infections are **endemic**, not epidemic. HSV is ubiquitous worldwide; most individuals are infected in childhood through direct contact with infected secretions (like saliva). It does not occur in large-scale seasonal outbreaks or localized epidemics but rather persists in the population through continuous transmission and lifelong latency. **Analysis of other options:** * **Option A & B:** Primary HSV-1 infection in children most commonly manifests as **Acute Herpetic Gingivostomatitis** [1]. It characteristically involves the **anterior portion of the mouth**, including the gingiva (gums), tongue, and labial mucosa, presenting with painful vesicles that rupture into ulcers [1]. * **Option D:** Primary infections are frequently preceded by **prodromal symptoms** such as high-grade fever, malaise, irritability, and regional lymphadenopathy before the appearance of oral lesions [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Latency:** HSV-1 remains latent in the **Trigeminal ganglion**, while HSV-2 typically resides in the **Sacral ganglia**. * **Diagnosis:** The gold standard for rapid bedside diagnosis is the **Tzanck Smear**, which shows **Multinucleated Giant Cells** with Cowdry Type A inclusion bodies [1]. * **Histopathology:** Look for "acantholysis," "ballooning degeneration" of keratinocytes, and "margination of chromatin" [1]. * **Encephalitis:** HSV-1 is the most common cause of sporadic fatal viral encephalitis, typically involving the **temporal lobes** [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 365-366. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1278.

Q: Which of the following is NOT a disease caused by coxsackievirus?

Herpes. **Explanation:** The correct answer is **D. Herpes**. This is because Herpes is caused by the **Herpes Simplex Virus (HSV)**, a DNA virus belonging to the *Herpesviridae* family [1]. In contrast, Coxsackievirus is a member of the *Picornaviridae* family (genus Enterovirus) and is a positive-sense RNA virus. **Analysis of Options:** * **Herpangina (Option A):** Characterized by fever, sore throat, and small vesicular/ulcerative lesions on the posterior oropharynx (tonsillar pillars, soft palate). It is primarily caused by **Coxsackievirus Group A**. * **Hand, Foot, and Mouth Disease (Option B):** A common childhood illness presenting with vesicular eruptions on the palms, soles, and oral mucosa. It is most commonly caused by **Coxsackievirus A16** (and Enterovirus 71). * **Acute Lymphonodular Pharyngitis (Option C):** A variant of pharyngitis where white-to-yellow nodules (packed lymphocytes) appear on the posterior pharynx. This is specifically associated with **Coxsackievirus A10**. **NEET-PG High-Yield Pearls:** * **Coxsackie Group A:** Primarily affects mucous membranes and skin (Herpangina, HFMD). * **Coxsackie Group B:** Primarily affects the heart and body walls. It is the most common cause of **viral myocarditis** and **pericarditis**, as well as **Bornholm disease** (epidemic pleurodynia/Devil’s grip). * **Aseptic Meningitis:** Both Group A and B can cause viral meningitis, but Group B is more frequently implicated. * **Type 1 Diabetes:** Coxsackie B4 has been epidemiologically linked to the triggering of islet cell antibodies. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 366.

Question 1

A 45-year-old HIV-positive male presented with dysphagia. Endoscopy and biopsy were performed. What is the most likely diagnosis based on the endoscopic and histological findings?

Accepted Answer

Cytomegalovirus (CMV) esophagitis

Answer

Herpes esophagitis

Answer

Candida esophagitis

Answer

Pseudomonas esophagitis

Question 2

Which of the following is the brownish-colored substance seen in heart failure cells?

Accepted Answer

Hemosiderin

Answer

Lipofuscin

Answer

Myoglobin

Answer

Bilirubin

Question 3

What is the multifocal tumor of vascular origin commonly seen in a patient with AIDS?

Accepted Answer

Kaposi sarcoma

Answer

Astrocytoma

Answer

Gastric Carcinoma

Answer

Primary CNS lymphoma

Question 4

Hepatitis B virus (HBV) infection is associated with all of the following conditions except:

Accepted Answer

Hepatic adenoma

Answer

Hepatic cancer

Answer

Chronic hepatitis

Answer

Cirrhosis

Question 5

Erythrophagia and Mononuclear cell infiltration ulcers are seen in which condition?

Accepted Answer

Typhoid ulcers

Answer

Necrotising colitis

Answer

Ulcerative colitis

Answer

Crohn's disease

Question 6

In Tuberculosis, what type of cells primarily provide immunity?

Accepted Answer

CD4+ cells

Answer

CD8+ cells

Answer

IgG antibodies

Answer

IgM antibodies

Question 7

A 37-year-old man presents with a productive cough, fever, and night sweats. A chest X-ray reveals an ill-defined area of consolidation at the periphery of the right middle lobe and mediastinal lymphadenopathy. Sputum culture is positive for acid-fast bacilli. What pathologic finding is most likely to be seen in a lymph node biopsy from this patient?

Accepted Answer

Caseating granulomas

Answer

Follicular hyperplasia

Answer

Nodular amyloidosis

Answer

Noncaseating granulomas

Question 8

Which of the following statements is NOT TRUE regarding primary Herpes Simplex Virus (HSV) infections?

Accepted Answer

Occurs epidemically.

Answer

Primarily affects the anterior portion of the mouth.

Answer

Causes acute gingivostomatitis.

Answer

Is often preceded by prodromal symptoms.

Question 9

Which of the following is NOT a disease caused by coxsackievirus?

Accepted Answer

Herpes

Answer

Herpangina

Answer

Hand, foot, and mouth disease

Answer

Acute lymphonodular pharyngitis

Question 10

Which of the following statements regarding Viridans streptococci is TRUE?

Accepted Answer

Reliably produces hemolysis on blood agar plates.

Answer

Includes Streptococcus mutans, mitis, sanguis, and salivarius.

Answer

Accounts for few cases of infective endocarditis.

Answer

The main strains of cariogenic streptococcus.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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