Infectious Diseases Practice Questions

Q: Which staining technique is considered the most reliable for detecting Cytomegalovirus (CMV) inclusions in tissue samples?

Immunohistochemistry (IHC). ***Immunohistochemistry (IHC)*** - **IHC** uses specific antibodies to detect **viral antigens** present within infected cells, offering high **sensitivity** and **specificity** for CMV [1]. - It effectively highlights **CMV-infected cells**, even those without classic viral inclusions, making it the most reliable method [1]. *Hematoxylin and eosin staining (H&E)* - While H&E can identify classic **CMV inclusions** (e.g., "owl's eye" appearance), its **sensitivity** is limited, especially in early or focal infections [1]. - It relies on morphological changes which might be subtle or absent, leading to potential **false negatives**. *Periodic acid-Schiff (PAS) staining* - PAS staining is primarily used to detect **carbohydrates** like glycogen, mucin, and fungal elements, not viral components [1]. - It is not specific for viral inclusions and would not reliably detect **CMV infection**. *Giemsa staining* - Giemsa stain is useful for identifying certain bacteria, parasites, and fungi, and can show some nuclear morphology, but it is not specific for **CMV viral inclusions** [1]. - It lacks the **specificity** and **sensitivity** of IHC for detecting viral antigens and distinguishing CMV from other cellular changes. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 362.

Q: An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node examination showed the following findings. What could be the diagnosis?

Tuberculosis. ***Tuberculosis*** - The image shows **caseating granulomas**, characterized by a central area of amorphous, eosinophilic necrosis (caseation) surrounded by epithelioid histiocytes, lymphocytes, and often Langhans giant cells. This is a classic histological feature of **tuberculosis**. - Cervical lymphadenopathy (scrofula) in a child, especially with a history of cough, is highly suggestive of **tuberculous lymphadenitis**. *Leprosy* - Leprosy typically presents with **granulomas that are non-caseating** or show foamy macrophages due to intracellular bacilli, depending on the type (tuberculoid vs. lepromatous). **Caseation is not a prominent feature.** - **Skin lesions and neurological involvement** (e.g., nerve thickening) are more characteristic of leprosy than isolated cervical lymphadenopathy. *Sarcoidosis* - Sarcoidosis is characterized by **non-caseating granulomas** in affected tissues, which is distinct from the caseating necrosis seen here. - While sarcoidosis can cause lymphadenopathy, the presence of **caseation rules out sarcoidosis**. *Syphilis* - Lymphadenopathy in syphilis often shows **follicular hyperplasia and diffuse paracortical expansion** with plasma cell infiltration and prominent vascularity. - **Granulomas, especially caseating ones, are not characteristic** of syphilitic lymphadenopathy.

Q: In tuberculosis the cytokine causing fever is

IL-1. ***ILI*** - **IL-1** plays a crucial role in the inflammatory response to tuberculosis, leading to symptoms such as **fever** and **malaise**. - It is primarily produced by activated **macrophages** in response to the presence of Mycobacterium tuberculosis [1]. *IL4* - IL-4 is mainly involved in **B-cell activation** and is associated with **allergic responses**, not directly causing fever. - Its role does not include the **pro-inflammatory** response seen in tuberculosis infections [2]. *IL3* - IL-3 is involved in the **stimulation of hematopoiesis**, promoting the growth of various blood cells. - It does not have a significant role in **fever** or inflammation associated with tuberculosis. *IL2* - IL-2 is primarily associated with the activation and proliferation of **T-cells**, playing a role in **adaptive immunity**, not acute inflammatory responses. - It is less related to the **fever** response seen in active tuberculosis infection. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 380-381. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 380.

Q: Warthin-Finkeldey cells are seen in

Measles infection. ***Measles infection*** - **Warthin-Finkeldey cells** are characteristic large, multinucleated giant cells with acidophilic intranuclear and intracytoplasmic inclusions found in lymphoid tissues during the prodromal phase of **measles** [1]. - These cells result from the fusion of measles virus-infected lymphocytes and are a **histological hallmark** of the disease [1]. *Rubella infection* - Rubella, or German measles, typically presents with a milder rash and **arthralgia** in adults. - While it is a viral infection, it does **not characteristically form Warthin-Finkeldey cells** in lymphoid tissue. *Rabies infection* - Rabies is a viral encephalitis primarily affecting the nervous system. - The characteristic histological finding in rabies is the presence of **Negri bodies** (eosinophilic inclusions) in the cytoplasm of neurons, not Warthin-Finkeldey cells in lymphoid tissue. *Typhoid infection* - Typhoid fever is a **bacterial infection** caused by *Salmonella Typhi*. - Histological features include **macrophage hyperplasia** and **typhoid nodules** in lymphoid tissues (like Peyer's patches), but not Warthin-Finkeldey cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 362-363.

Q: Stellate granulomas are seen in

Cat scratch disease. ***Cat scratch disease*** - **Stellate granulomas** are a characteristic histological feature of **Cat scratch disease**, caused by **Bartonella henselae**. - These granulomas are composed of macrophages, lymphocytes, and neutrophils arranged in a **star-shaped or stellate pattern**, often with central necrosis. *Sarcoidosis* - Sarcoidosis is characterized by **non-caseating granulomas**, which are typically well-formed and discrete [2], [3]. - However, they do not usually have the distinct **stellate (star-shaped) morphology** seen in cat scratch disease [3]. *Cryptococcosis* - Cryptococcosis is a fungal infection that typically presents with **granulomas containing yeasts** within macrophages. - The granulomas formed in cryptococcosis are not classically described as **stellate granulomas**. *Histoplasmosis* - Histoplasmosis is another fungal infection that can cause granuloma formation, usually with **caseous necrosis** similar to tuberculosis [1]. - The granulomas in histoplasmosis do not exhibit the **stellate architectural pattern** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 198-200. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 700-701.

Q: ABO non- secretors are more prone to ?

Increased risk of infections. Increased risk of infections - Non-secretors of ABO antigens exhibit an increased susceptibility to a variety of infections, particularly bacterial and viral pathogens. - This is thought to be due to the absence of ABO antigens in secretions, which typically act as decoy receptors to prevent pathogen adhesion to host cells. Autoimmune diseases - While some associations between ABO blood groups and autoimmune diseases exist, non-secretor status is not consistently linked to a higher overall risk of autoimmune conditions. Cardiovascular diseases - ABO blood groups have been associated with cardiovascular risk, with non-O blood types generally having a slightly higher risk of certain cardiovascular events. - However, secretor status (the ability to secrete ABO antigens into bodily fluids) itself is not a prominent independent risk factor for cardiovascular diseases. Cancer - There are some documented associations between specific ABO blood types and certain types of cancer (e.g., non-O blood types with pancreatic cancer), but this is distinct from secretor status. - Being an ABO non-secretor is not a primary, broadly recognized risk factor for developing cancer.

Q: Primary complex of M bovis involves:

Tonsil and intestine. ***Tonsil and intestine*** - *Mycobacterium bovis* is primarily transmitted through **consumption of contaminated milk and dairy products**, making the **alimentary tract** the main route of infection - The primary complex (Ghon complex) involves the **initial site of infection plus regional lymph nodes** - In alimentary tuberculosis, the organisms enter through the **intestinal mucosa** (Peyer's patches) or **tonsillar tissue**, creating foci with associated mesenteric or cervical lymphadenopathy - Both tonsils and intestines are part of the **alimentary system**, representing the typical primary complex for M. bovis in humans *Tonsil and lung* - This incorrectly combines **two different routes of entry** (alimentary and respiratory) - A primary complex involves a **single portal of entry**, not multiple unrelated organ systems - While M. bovis can rarely cause pulmonary TB through inhalation, this would create a separate lung + hilar node complex, not a combined tonsil-lung complex *Tonsil and skin* - **Skin involvement** requires direct inoculation through cuts or abrasions and does not form a primary complex with tonsillar infection - These represent different portals of entry and would not occur together as a primary complex *Skin and Intestine* - **Skin infection** by M. bovis is rare and requires occupational exposure with direct inoculation (e.g., veterinarians, butchers) - This incorrectly pairs two different routes of infection that would not form a single primary complex

Q: What does Ghon's focus indicate in the context of tuberculosis?

Primary complex. ***Primary complex*** - A **Ghon's focus** is the initial parenchymal lesion (typically subpleural) that develops during primary tuberculosis infection [1]. - The Ghon's focus, together with an enlarged regional lymph node (usually hilar or mediastinal), forms the **Ghon's complex** or **Primary complex** [2]. - When this complex undergoes calcification and healing, it is called a **Ranke complex**, which indicates past healed primary TB. *Post primary tuberculosis* - Also known as **reactivation tuberculosis** or **secondary tuberculosis**, this typically occurs years after the primary infection, usually in the apices of the lungs [2]. - It represents reactivation of dormant bacilli, not the initial primary infection lesion. - Characterized by cavitary lesions and often more severe pulmonary symptoms. *Miliary tuberculosis* - This is a form of progressive, widespread tuberculosis characterized by the presence of **tiny, millet-seed sized lesions** disseminated throughout the body via hematogenous spread [3]. - It indicates a severe and life-threatening form of TB resulting from massive lymphohematogenous dissemination. - Not related to the localized primary complex. *Tuberculous lymphadenitis* - This refers to **tuberculous infection of lymph nodes**, most commonly in the cervical region (scrofula). - While lymph node involvement is part of the primary complex, Ghon's focus specifically refers to the **parenchymal lung lesion**, not the lymph node component alone [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 379-380. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 319-320. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 320-321.

Q: The histological feature known as 'Mickey Mouse Ears' is characteristically seen in:

Paracoccidioidomycosis. ***Paracoccidioidomycosis*** - This characteristic appearance, often described as a **"ship's wheel"** or **"Mickey Mouse ears"**, refers to the multiple budding yeast cells seen in **Paracoccidioides brasiliensis** on histological examination. - The central mother cell has several smaller daughter buds emerging from its periphery, resembling the iconic Mickey Mouse ears. *Candidiasis* - **Candida** infections typically manifest as **pseudohyphae** and **budding yeast** cells, but they do not form the multi-budding, "Mickey Mouse ears" configuration [1]. - The budding of Candida is usually singular or in short chains, distinct from the broad-based multi-budding of Paracoccidioides [1]. *Tuberculosis* - **Tuberculosis** is caused by **Mycobacterium tuberculosis**, a bacterium, and is characterized histologically by **granulomas** with caseous necrosis. - It does not involve yeast forms or the "Mickey Mouse ears" morphology. *Leptospirosis* - **Leptospirosis** is a **bacterial infection** caused by **Leptospira interrogans**, a spirochete, which is seen as spiral-shaped bacteria under microscopy. - This disease affects various organs and is not associated with fungal yeast forms or the "Mickey Mouse ears" appearance. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 736-737.

Question 1

Which staining technique is considered the most reliable for detecting Cytomegalovirus (CMV) inclusions in tissue samples?

Accepted Answer

Immunohistochemistry (IHC)

Answer

Hematoxylin and eosin staining (H&E)

Answer

Periodic acid-Schiff (PAS) staining

Answer

Giemsa staining

Question 2

An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node examination showed the following findings. What could be the diagnosis?

Accepted Answer

Tuberculosis

Answer

Leprosy

Answer

Sarcoidosis

Answer

Syphilis

Question 3

In tuberculosis the cytokine causing fever is

Accepted Answer

IL-1

Answer

IL-2

Answer

IL-3

Answer

IL-4

Question 4

Warthin-Finkeldey cells are seen in

Accepted Answer

Measles infection

Answer

Rubella infection

Answer

Rabies infection

Answer

Typhoid infection

Question 5

Stellate granulomas are seen in

Accepted Answer

Cat scratch disease

Answer

Sarcoidosis

Answer

Cryptococcosis

Answer

Histoplasmosis

Question 6

ABO non- secretors are more prone to ?

Accepted Answer

Increased risk of infections

Answer

Autoimmune diseases

Answer

Cardiovascular diseases

Answer

Cancer

Question 7

Primary complex of M bovis involves:

Accepted Answer

Tonsil and intestine

Answer

Tonsil and skin

Answer

Tonsil and lung

Answer

Skin and Intestine

Question 8

What does Ghon's focus indicate in the context of tuberculosis?

Accepted Answer

Primary complex

Answer

Post primary tuberculosis

Answer

Miliary tuberculosis

Answer

Tuberculous lymphadenitis

Question 9

The histological feature known as 'Mickey Mouse Ears' is characteristically seen in:

Accepted Answer

Paracoccidioidomycosis

Answer

Tuberculosis

Answer

Candidiasis

Answer

Leptospirosis

Question 10

What are the histological characteristics of Lepra cells in lepromatous leprosy?

Accepted Answer

Foamy macrophages (Histiocytes)

Answer

Neutrophils

Answer

Plasma cells

Answer

Epithelioid cells

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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