Opportunistic Fungal Infections — MCQs
A man has undergone renal transplant and is taking immunosuppressant drug. On biopsy there was presence of budding cells with pseudohyphae. Identify the organism?
A patient with AIDS presents with meningitis. India ink staining shows encapsulated yeasts. Which organism is most likely?
HIV patient presents with chest X-ray showing bilateral reticulonodular infiltrates. CD4 count 80/µL. Most likely diagnosis?
In HIV patients, Kaposi's sarcoma is most likely caused by which of the following?
Which of the following is not a characteristic feature of bronchopulmonary aspergillosis?
A biopsy of a lung nodule from a patient with a history of bird exposure reveals yeast cells with thick capsules. What is the most likely pathogen?
The classic opportunistic infection in acquired immune deficiency syndrome is:
A 60-year-old female with a history of diabetes presents with nasal congestion, facial pain, and black necrotic patches on the palate. What is the most likely diagnosis?
Which of the following statements about Penicillium marneffei is incorrect?
Beta 1,3 Glucan test is positive in all except?
Opportunistic Fungal Infections Indian Medical PG Practice Questions and MCQs
Question 1: A man has undergone renal transplant and is taking immunosuppressant drug. On biopsy there was presence of budding cells with pseudohyphae. Identify the organism?
- A. Invasive candidiasis (Correct Answer)
- B. Pneumocystis
- C. Invasive aspergillosis
- D. Histoplasmosis
Explanation: ***Invasive candidiasis*** - The presence of **budding cells** and **pseudohyphae** on biopsy is a classic histological finding for *Candida* species. - Individuals who have undergone **renal transplant** and are on **immunosuppressant drugs** are at high risk for opportunistic fungal infections, including invasive candidiasis. *Pneumocystis* - *Pneumocystis jirovecii* typically causes pneumonia and is characterized by cysts or trophic forms in lung tissue, not budding cells and pseudohyphae. - While common in immunocompromised patients, its microscopic morphology is distinctly different from *Candida*. *Invasive aspergillosis* - *Aspergillus* species are characterized by **septate hyphae with acute angle branching** (typically 45-degree angles) on microscopy. - They do not form budding cells or pseudohyphae, which are characteristic of *Candida*. *Histoplasmosis* - *Histoplasma capsulatum* appears as **small, oval-shaped yeast cells** (2-4 µm) often found within macrophages. - It does not form pseudohyphae or large budding cells as described in the question.
Question 2: A patient with AIDS presents with meningitis. India ink staining shows encapsulated yeasts. Which organism is most likely?
- A. Candida albicans
- B. Cryptococcus neoformans (Correct Answer)
- C. Histoplasma capsulatum
- D. Coccidioides immitis
Explanation: ***Cryptococcus neoformans*** - This fungus is a common cause of **meningitis in AIDS patients** and characteristically appears as **encapsulated yeasts** on India ink staining of CSF. - The capsule excludes the ink, creating a distinct **halo** around the yeast cell, which is diagnostic. *Candida albicans* - While *Candida* can cause systemic infections, including meningitis, it typically presents as **pseudohyphae** or budding yeast without an obvious capsule on India ink stain. - *Candida meningitis* is less common in AIDS patients compared to *Cryptococcus*. *Histoplasma capsulatum* - This is a dimorphic fungus that causes **histoplasmosis**, often disseminated in AIDS patients, but typically manifests as **pulmonary disease** or hepatosplenomegaly. - It appears as small, **intracellular yeasts** within macrophages and would not show an encapsulated form on India ink stain in CSF. *Coccidioides immitis* - This dimorphic fungus causes **coccidioidomycosis**, which can lead to meningitis, particularly in immunocompromised individuals. - In CSF, it is seen as **spherules containing endospores**, not encapsulated yeasts, which is a distinct morphological feature.
Question 3: HIV patient presents with chest X-ray showing bilateral reticulonodular infiltrates. CD4 count 80/µL. Most likely diagnosis?
- A. CMV infection
- B. Pneumocystis pneumonia (Correct Answer)
- C. Cryptococcosis
- D. Tuberculosis
Explanation: ***Pneumocystis pneumonia (PCP)*** - **Pneumocystis pneumonia** is a common opportunistic infection in HIV patients with a **CD4 count below 200 cells/L**, and a CD4 count of 80/L makes it highly likely [1]. - The classic chest X-ray finding for PCP is **bilateral interstitial or reticulonodular infiltrates**, which matches the patient's presentation [1]. *CMV infection* - While **cytomegalovirus (CMV) infection** can occur in advanced HIV disease, pulmonary involvement typically presents with **pneumonitis** or **pleural effusions** rather than exclusively reticulonodular infiltrates. - CMV pneumonitis often manifests with other organ involvement like **retinitis** or **colitis**, which are not mentioned here. *Cryptococcosis* - **Cryptococcus neoformans** primarily causes **meningitis** in HIV patients, though pulmonary cryptococcosis can occur. - Pulmonary involvement often presents as solitary or multiple **nodules** or **masses**, rather than diffuse reticulonodular infiltrates. *Tuberculosis* - **Tuberculosis (TB)** is common in HIV patients and can present with various radiographic patterns, including infiltrates, nodules, or cavitation [1]. - However, in advanced HIV (low CD4 count), **extrapulmonary TB** and atypical presentations are more common, and while pulmonary infiltrates occur, **PCP** is more classically associated with diffuse reticulonodular infiltrates in this specific CD4 range [1].
Question 4: In HIV patients, Kaposi's sarcoma is most likely caused by which of the following?
- A. Bacteria
- B. Parasite
- C. Fungus
- D. Virus (Correct Answer)
Explanation: ***Virus*** - The image likely depicts **Kaposi's sarcoma**, a common lesion in HIV patients, which is caused by **Human Herpesvirus 8 (HHV-8)**. - Other viral infections like **Herpes Simplex Virus (HSV)** can also cause mucocutaneous lesions in immunocompromised individuals. *Bacteria* - While HIV patients are susceptible to bacterial infections (e.g., **Staphylococcus aureus** causing skin abscesses), the described lesion type is not characteristic of common bacterial skin infections. - Bacterial lesions often present as pustules, cellulitis, or ulcers with purulent discharge, which differ from typical Kaposi's sarcoma. *Parasite* - Parasitic infections can occur in HIV patients (e.g., **scabies** or **leishmaniasis**), but these typically present with different dermatological features like intensely itchy papules or nodular ulcerative lesions. - Lesions caused by parasites do not usually manifest as the violaceous, nodular, or plaque-like appearances seen in Kaposi's sarcoma. *Fungus* - Fungal infections in HIV patients can cause skin lesions (e.g., **candidiasis** with oral thrush or esophagitis, or **cryptococcosis** with molluscum-like lesions). - However, the morphology of these fungal lesions generally differs from the classic appearance of Kaposi's sarcoma or other common viral lesions in HIV.
Question 5: Which of the following is not a characteristic feature of bronchopulmonary aspergillosis?
- A. Central bronchiectasis
- B. Eosinophilia
- C. Asthma
- D. Pleural effusion (Correct Answer)
Explanation: ***Pleural effusion*** - While other fungal infections can cause pleural effusions, **bronchopulmonary aspergillosis (ABPA)** rarely causes exudative effusions. - The primary pathology in ABPA involves **allergic inflammation within the airways**, rather than invasive disease extending to the pleura. *Central bronchiectasis* - **Central bronchiectasis** is a hallmark feature of ABPA, particularly affecting the upper and middle lobes due to mucin impaction and inflammation. - This is a direct consequence of the extensive **allergic inflammatory response** to *Aspergillus* antigens within the bronchial tree. *Asthma* - **Asthma** is a prerequisite for a diagnosis of ABPA, as the disease stems from an exaggerated immune response to *Aspergillus* in asthmatic individuals [1]. - Patients typically present with difficult-to-control asthma, often with **recurrent exacerbations** and a need for high-dose corticosteroids. *Eosinophilia* - **Peripheral blood eosinophilia** is a common laboratory finding in ABPA, reflecting the intense **Type I and Type III hypersensitivity reactions** [1]. - This eosinophilic inflammation is central to the pathogenesis, contributing to airway damage and mucus plugging.
Question 6: A biopsy of a lung nodule from a patient with a history of bird exposure reveals yeast cells with thick capsules. What is the most likely pathogen?
- A. Aspergillus fumigatus
- B. Blastomyces dermatitidis
- C. Histoplasma capsulatum
- D. Cryptococcus neoformans (Correct Answer)
Explanation: ***Cryptococcus neoformans*** - The presence of **yeast cells with thick capsules** is a classic histological finding for *Cryptococcus neoformans*. - While *Cryptococcus* commonly affects immunocompromised individuals, it can also be found in **bird droppings**, particularly from pigeons, making the history of bird exposure relevant. *Aspergillus fumigatus* - *Aspergillus fumigatus* typically presents as **hyphae**, not yeast cells, and would not have a thick capsule. - Infections often manifest as **aspergillomas** (fungus balls) in lung cavities or invasive disease in immunocompromised patients. *Blastomyces dermatitidis* - *Blastomyces dermatitidis* appears as **large, broad-based budding yeast cells** but does not possess a thick capsule. - It is typically found in the **soil**, especially in moist areas, and its association with bird exposure is not as strong as with *Cryptococcus*. *Histoplasma capsulatum* - *Histoplasma capsulatum* is characterized by **small intracellular yeast forms** within macrophages and does not have a thick capsule. - It is strongly associated with **bird and bat droppings** but its microscopic appearance is distinct from that described.
Question 7: The classic opportunistic infection in acquired immune deficiency syndrome is:
- A. Aphthous stomatitis
- B. Tuberculosis
- C. Pneumocystis jirovecii pneumonia (Correct Answer)
- D. Herpetic gingivostomatitis
Explanation: ***Pneumocystis jirovecii pneumonia*** - **Pneumocystis jirovecii pneumonia (PJP)** is a classic and common opportunistic infection in individuals with **AIDS**, especially when the **CD4 count drops below 200 cells/mm³** [1]. - It presents with fever, dyspnea, non-productive cough, and hypoxia, and is a major cause of morbidity and mortality in untreated HIV. *Aphthous stomatitis* - While common in HIV-positive individuals, **aphthous stomatitis** is not typically considered an **opportunistic infection** or an **AIDS-defining illness** [2]. - It represents a painful inflammation of the oral mucosa, often recurring due to local irritants or systemic factors, rather than a pathogen exploiting immunodeficiency. *Tuberculosis* - **Tuberculosis (TB)** is an opportunistic infection and a serious concern in HIV-infected individuals, but the question asks for the **classic** opportunistic infection in AIDS [1]. - While TB incidence is significantly higher in HIV-positive patients, **Pneumocystis jirovecii pneumonia** is historically and clinically more often cited as the classic infection associated with the initial presentation or diagnosis of AIDS. *Herpetic gingivostomatitis* - **Herpes simplex virus (HSV)** infections, including gingivostomatitis, are more frequent and severe in immunocompromised individuals. - However, **herpetic gingivostomatitis** is a specific manifestation that doesn't usually define AIDS as readily as **Pneumocystis jirovecii pneumonia**.
Question 8: A 60-year-old female with a history of diabetes presents with nasal congestion, facial pain, and black necrotic patches on the palate. What is the most likely diagnosis?
- A. Bacterial sinusitis
- B. Mucormycosis (Correct Answer)
- C. Rhinoscleroma
- D. Granulomatosis with Polyangiitis (GPA)
Explanation: ***Mucormycosis*** - The presence of **black necrotic patches on the palate** in a diabetic patient with sinusitis symptoms is highly characteristic of mucormycosis. - **Diabetes** is a significant risk factor for this aggressive fungal infection, which often presents with tissue necrosis. *Bacterial sinusitis* - While facial pain and nasal congestion are consistent with bacterial sinusitis, **black necrotic patches** are not a typical feature. - Bacterial sinusitis rarely causes deep tissue invasion and necrosis of this extent. *Rhinoscleroma* - This is a chronic granulomatous disease of the upper respiratory tract caused by *Klebsiella rhinoscleromatis*, primarily seen in specific endemic regions. - It presents with **progressive inflammatory masses** and **scarring**, not acute necrosis or black patches. *Granulomatosis with Polyangiitis (GPA)* - GPA can cause sinusitis, **nasal crusting**, and **cartilage destruction**, but typically presents with **granulomatous inflammation** and vasculitis, not primary necrotic patches on the palate. - It is often associated with **ANCA positivity** and systemic symptoms affecting the lungs and kidneys.
Question 9: Which of the following statements about Penicillium marneffei is incorrect?
- A. Forms black colonies (Correct Answer)
- B. Is a dimorphic fungus
- C. Amphotericin B is used for treatment
- D. Causes severe infections in immunocompromised patients
Explanation: ***Forms black colonies*** - *Penicillium marneffei* typically forms colonies that are often **reddish-beige** or **pigmented red-diffusible**, not black. - The production of a characteristic **red-to-burgundy pigment** is a key identifying feature of this fungus, especially in culture. *Is a dimorphic fungus* - This statement is correct. *Penicillium marneffei* is a **thermally dimorphic fungus**, meaning it grows as a mould at 25°C (room temperature) and as yeast-like cells at 37°C (body temperature). - This dimorphism is crucial for its pathogenesis and identification. *Amphotericin B is used for treatment* - This statement is correct. **Amphotericin B** is a commonly used antifungal agent for the treatment of severe *Penicillium marneffei* infections, particularly in immunocompromised patients. - It is often followed by a maintenance regimen with an azole antifungal like itraconazole. *Causes severe infections in immunocompromised patients* - This statement is correct. *Penicillium marneffei* is an **opportunistic pathogen** that primarily causes severe, disseminated infections in individuals with compromised immune systems, especially those with HIV/AIDS. - Endemic regions include Southeast Asia, where it is a leading cause of systemic mycosis in HIV-positive patients.
Question 10: Beta 1,3 Glucan test is positive in all except?
- A. Pneumocystis Jirovecii
- B. Candida
- C. Mucormycosis (Correct Answer)
- D. Aspergillus
Explanation: ***Mucormycosis*** - Fungi causing mucormycosis belong to the order **Mucorales**, which structurally lack **beta-D-glucan** in their cell walls. - Due to the absence of beta-D-glucan, the **beta-1,3-D-glucan assay** will yield a negative result in cases of mucormycosis. *Pneumocystis jirovecii* - This fungus contains significant amounts of **beta-D-glucan** in its cell wall, making the test usually positive during active infection. - A positive **beta-D-glucan test** can be a useful diagnostic marker for **Pneumocystis pneumonia (PCP)**, especially in immunocompromised patients. *Candida* - **Candida species** possess a cell wall rich in **beta-D-glucan**, leading to a positive test result during active infection. - The **beta-D-glucan assay** is a valuable adjunctive test for diagnosing invasive candidiasis. *Aspergillus* - The cell wall of **Aspergillus** contains **beta-D-glucan**, causing the test to be positive in cases of invasive aspergillosis. - A positive **beta-D-glucan test** can aid in the early diagnosis and management of invasive aspergillosis, particularly in high-risk patients.
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