Fungal and Parasitic Infections — MCQs
Which test is most specific for diagnosing invasive aspergillosis?
A 50-year-old woman with a history of rheumatoid arthritis presents with fever and joint pain. Which laboratory test is most definitive in distinguishing between a rheumatoid flare and an infectious process?
Which of the following is the carrying agent for Lyme disease?
A patient with known hemophilia presented with pain in his ankle. X-ray showed an osteolytic lesion with a sclerotic rim. What is your diagnosis?
A 40-year-old gardener presents with several subcutaneous nodules on his right hand, where he had cut himself on rose thorns, and physical examination reveals several erythematous fluctuant lesions. Which organism is most likely responsible for his condition?
A 40-year-old female with multiple sexual partners presented with fever, rash, and articular symptoms. Migratory arthritis and tenosynovitis of knees, hands, wrists, feet, and ankles were noticed during clinical examination. Synovial fluid leukocyte count was 12,000/ml and culture was sterile. The patient has been successfully treated with injection ceftriaxone 1 g Q24 hours for 7 days. What was the diagnosis in this setting?
Which of the following conditions is NOT typically associated with eosinophilic meningitis?
A 25-year-old male presents with localized pain in the tibia and swelling. Imaging reveals a bone abscess. Identify the condition.
A 18-year-old boy presents with tenderness, warmth over the bone, and fever, ESR and CRP levels. The radiograph is shown below. What is the most likely diagnosis?
A 28-year-old male with a history of trauma presents with a non-healing sinus on the tibia. An X-ray shows a sequestrum. What is the appropriate next step in management?
Fungal and Parasitic Infections Indian Medical PG Practice Questions and MCQs
Question 1: Which test is most specific for diagnosing invasive aspergillosis?
- A. Culture
- B. Beta-D-glucan assay
- C. Microscopy
- D. Galactomannan test (Correct Answer)
Explanation: ***Galactomannan test*** - The **galactomannan test** detects a polysaccharide component of the *Aspergillus* cell wall, making it specific for *Aspergillus* species. - A positive result, especially in high-risk patients, strongly indicates **invasive aspergillosis** due to its high specificity. *Culture* - While culture can identify *Aspergillus*, it lacks specificity as it can grow as a **contaminant** in respiratory samples. - Recovery of *Aspergillus* from routine cultures does not always confirm invasive disease, often requiring additional evidence. *Beta-D-glucan assay* - The **beta-D-glucan assay** detects a pan-fungal cell wall component, meaning it is not specific to *Aspergillus*. - A positive result can indicate a wide range of **invasive fungal infections**, including candidiasis and pneumocystosis, but does not differentiate them. *Microscopy* - Microscopic examination can reveal **fungal elements** consistent with *Aspergillus* (e.g., septate hyphae with acute angle branching). - However, morphology alone is not definitive and requires confirmatory tests for species identification and to distinguish from other filamentous fungi.
Question 2: A 50-year-old woman with a history of rheumatoid arthritis presents with fever and joint pain. Which laboratory test is most definitive in distinguishing between a rheumatoid flare and an infectious process?
- A. Erythrocyte sedimentation rate (ESR)
- B. Joint aspiration and culture (Correct Answer)
- C. C-reactive protein (CRP)
- D. Rheumatoid factor (RF)
Explanation: Detailed joint aspiration and culture is the most definitive step [1]. This procedure directly analyzes synovial fluid for **white blood cells**, **bacteria**, or **crystals**, providing a definitive diagnosis for an infectious process such as **septic arthritis** [1]. *Erythrocyte sedimentation rate (ESR)* - While elevated in both inflammation and infection, the **ESR is a non-specific marker** and cannot differentiate between a rheumatoid flare and an infectious process. - It indicates overall inflammation but does not identify the underlying cause of the inflammation. *C-reactive protein (CRP)* - Similar to ESR, **CRP is an acute-phase reactant** [2]. It increases significantly during both inflammatory conditions and infections [2]. - It is a more sensitive marker for inflammation than ESR but **lacks specificity** to distinguish between inflammatory and infectious etiologies [2]. *Rheumatoid factor (RF)* - **Rheumatoid factor** is an autoantibody primarily associated with **rheumatoid arthritis** and is usually present in patients with the disease. - Its presence or elevated levels would not differentiate between an RA flare and a concurrent infection, as it reflects the underlying autoimmune disease rather than an acute infectious process.
Question 3: Which of the following is the carrying agent for Lyme disease?
- A. Anopheles
- B. Ixodes scapularis ticks (Correct Answer)
- C. Louse
- D. Rat flea
Explanation: ***Ixodes scapularis ticks*** - *Ixodes scapularis* ticks (deer ticks) are the primary **vectors for Lyme disease** (caused by *Borrelia burgdorferi*) in North America [1]. - In Europe, *Ixodes ricinus* is the main vector for Lyme disease. - Lyme disease presents with characteristic **erythema migrans** rash, followed by potential neurological, cardiac, and arthritic complications [1]. - Lyme arthritis commonly affects large joints, particularly the **knee**, causing inflammatory arthritis [1]. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria**, not Lyme disease [2]. - Malaria is caused by *Plasmodium* parasites and presents with fever, chills, and hemolytic anemia [2]. *Louse* - **Lice** are vectors for diseases such as **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever** (caused by *Borrelia recurrentis*) [3]. - They are not associated with the transmission of Lyme disease. *Rat flea* - **Rat fleas** (e.g., *Xenopsylla cheopis*) are the primary vectors for **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus**. - These insects do not transmit Lyme disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 389-390. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 400. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 392-393.
Question 4: A patient with known hemophilia presented with pain in his ankle. X-ray showed an osteolytic lesion with a sclerotic rim. What is your diagnosis?
- A. Hemophilic pseudotumor
- B. PVNS (Correct Answer)
- C. Giant Cell Tumor
- D. Ochronosis
Explanation: ***
Question 5: A 40-year-old gardener presents with several subcutaneous nodules on his right hand, where he had cut himself on rose thorns, and physical examination reveals several erythematous fluctuant lesions. Which organism is most likely responsible for his condition?
- A. Aspergillus
- B. Malassezia
- C. Sporothrix (Correct Answer)
- D. Histoplasma
Explanation: ***Sporothrix*** - The gardener's history of a cut from rose thorns and the development of **subcutaneous nodules** are classic presentations of **sporotrichosis** (rose gardener's disease), caused by *Sporothrix schenckii*. - *Sporothrix schenckii* is a **dimorphic fungus** found in soil and on plant matter, causing localized cutaneous or subcutaneous lesions that typically follow **lymphatic spread** (lymphocutaneous pattern). *Aspergillus* - *Aspergillus* species typically cause **invasive pulmonary infections** (aspergillosis) in immunocompromised individuals or allergic bronchopulmonary aspergillosis. - While it can cause cutaneous infections, these are rare and usually occur in severely immunocompromised patients, without the classic "rose thorn" association. *Malassezia* - *Malassezia* species are yeasts that are normal skin flora and are primarily associated with **pityriasis versicolor**, **seborrheic dermatitis**, and **folliculitis**. - They do not typically cause deep subcutaneous nodules or are associated with puncture wounds from plants. *Histoplasma* - *Histoplasma capsulatum* is a **dimorphic fungus** that primarily causes **pulmonary infections** through inhalation of spores from soil contaminated with bird or bat droppings. - While it can rarely cause cutaneous lesions (especially in disseminated disease in immunocompromised patients), it is not associated with traumatic inoculation from plant material or the lymphocutaneous pattern seen here.
Question 6: A 40-year-old female with multiple sexual partners presented with fever, rash, and articular symptoms. Migratory arthritis and tenosynovitis of knees, hands, wrists, feet, and ankles were noticed during clinical examination. Synovial fluid leukocyte count was 12,000/ml and culture was sterile. The patient has been successfully treated with injection ceftriaxone 1 g Q24 hours for 7 days. What was the diagnosis in this setting?
- A. Disseminated gonococcal infection (Correct Answer)
- B. Gonococcal septic arthritis
- C. Syphilitic arthritis
- D. Arthritis due to Pseudomonas aeruginosa
Explanation: ***Disseminated gonococcal infection*** - The classic triad of **fever**, **rash**, and **articular symptoms (migratory polyarthralgia or tenosynovitis)** in a sexually active individual strongly suggests disseminated gonococcal infection (**DGI**). - The positive response to **ceftriaxone**, an antibiotic effective against *Neisseria gonorrhoeae*, further supports this diagnosis. *Gonococcal septic arthritis* - While *N. gonorrhoeae* can cause septic arthritis, it typically presents as a **monoarticular** joint infection with severe pain and swelling, not **migratory polyarthritis** and tenosynovitis. - The synovial fluid in septic arthritis would show a significantly **higher leukocyte count** (often >50,000 cells/mm³) and frequently a positive culture if bacteria are adequately cultured. *Syphilitic arthritis* - Syphilitic arthritis is uncommon and often presents in **secondary or tertiary syphilis**, characterized by chronic inflammation and unique bone lesions, not acute migratory polyarthritis or tenosynovitis. - The rash of secondary syphilis is typically **macropapular and non-pruritic**, often involving the palms and soles, which differs from the rash seen in DGI. *Arthritis due to Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* arthritis is rare and typically occurs in individuals with **immunocompromise**, **intravenous drug use**, or following **puncture wounds**, none of which are mentioned here. - The clinical picture of **migratory polyarthralgia and tenosynovitis** is not characteristic of *Pseudomonas* arthritis, which is usually purulent and monoarticular.
Question 7: Which of the following conditions is NOT typically associated with eosinophilic meningitis?
- A. Leptomeningeal metastasis (Correct Answer)
- B. Cryptococcal meningitis
- C. Coccidiomycosis
- D. Helminthic infections
Explanation: ***Leptomeningeal metastasis*** - This condition involves the spread of **malignant cells** to the leptomeninges, causing inflammation and neurological symptoms. - While it can cause inflammatory changes in the cerebrospinal fluid, it typically does not lead to a prominent **eosinophilic pleocytosis**. *Coccidiomycosis* - **Coccidioides immitis**, a dimorphic fungus, can cause **meningitis** and is a known cause of **eosinophilic meningitis**, particularly in endemic areas. - The fungal infection triggers a robust immune response that often involves an **eosinophil accumulation** in the CSF. *Cryptococcal meningitis* - Caused by **Cryptococcus neoformans** or **Cryptococcus gattii**, this fungal infection usually presents with **lymphocytic pleocytosis** or can have a normal cell count initially, especially in immunocompromised individuals. - Although it is a fungal infection, **eosinophilia** in the CSF is not a characteristic finding and is quite rare. *Helminthic infections* - Parasitic infections such as those caused by **Angiostrongylus cantonensis** (rat lungworm), **Gnathostoma spinigerum**, or **Taenia solium** (cysticercosis) are common causes of eosinophilic meningitis. - The immune response to the presence of these **helminths** in the central nervous system often involves a significant influx of eosinophils into the CSF.
Question 8: A 25-year-old male presents with localized pain in the tibia and swelling. Imaging reveals a bone abscess. Identify the condition.
- A. Brodie abscess (Correct Answer)
- B. Osteoid osteoma
- C. Intracortical hemangioma
- D. Chondromyxoid fibroma
Explanation: ***Brodie abscess*** - A Brodie abscess is a **subacute or chronic osteomyelitis** characterized by a well-circumscribed, **radiolucent lesion** (an abscess cavity) often surrounded by a zone of **sclerosis**, representing the body's attempt to wall off the infection. - The presentation of localized pain and swelling in the tibia, with imaging revealing a bone abscess, is consistent with this condition, which is a common form of localized osteomyelitis. *Osteoid osteoma* - This is a **benign bone tumor** characterized by a small, radiolucent nidus surrounded by a large area of **sclerotic bone**. The pain from an osteoid osteoma is typically **worse at night** and dramatically relieved by NSAIDs. - While it can cause localized pain and swelling, the imaging features of a distinct abscess cavity are not characteristic of an osteoid osteoma. *Intracortical hemangioma* - An intracortical hemangioma is a **rare benign vascular lesion** within the cortex of a bone. - Imaging typically shows a **lytic lesion** with a characteristic **"honeycomb" or "sunburst" appearance**, not a well-defined abscess. *Chondromyxoid fibroma* - This is a rare, **benign cartilaginous tumor** that usually presents as an **eccentric lytic lesion** in the metaphysis of long bones, often with a scalloped border and sclerotic rim. - While it can cause localized pain and swelling, the imaging appearance of an abscess with sclerotic margins is not typical of a chondromyxoid fibroma.
Question 9: A 18-year-old boy presents with tenderness, warmth over the bone, and fever, ESR and CRP levels. The radiograph is shown below. What is the most likely diagnosis?
- A. Ewing's sarcoma
- B. Osteosarcoma
- C. Osteomyelitis (Correct Answer)
- D. Giant cell tumor
Explanation: ***Osteomyelitis*** - The clinical presentation of **fever, localized tenderness, and warmth** with elevated **ESR and CRP** levels in an 18-year-old is highly suggestive of **osteomyelitis**, an infection of the bone. - Radiographs in acute osteomyelitis may show soft tissue swelling, periosteal reaction, and areas of **bone destruction**, which can be subtle early in the infection. *Ewing's sarcoma* - This typically presents with local pain and swelling, and can also cause fever and elevated inflammatory markers. - However, characteristic radiographic findings such as an **"onion skin" periosteal reaction** or a **"moth-eaten" appearance** are not clearly visible here. *Osteosarcoma* - This is a primary malignant bone tumor often seen in adolescents, presenting with localized pain and swelling. - Radiographic features typically include a **Codman triangle**, **sunburst appearance**, or a **mixed lytic and blastic lesion**, which are not seen in this image. *Giant cell tumor* - Usually occurs in **young adults (20-40 years old)**, not typically in an 18-year-old, and presents with pain and swelling around the joint. - Radiographically, it is characterized by an **eccentric lytic lesion** in the **epiphysis or metaphysis** of long bones, often described as a **"soap bubble" appearance**, which is not depicted here.
Question 10: A 28-year-old male with a history of trauma presents with a non-healing sinus on the tibia. An X-ray shows a sequestrum. What is the appropriate next step in management?
- A. Systemic antibiotics
- B. Local wound care
- C. Sequestrectomy (Correct Answer)
- D. Bone grafting
Explanation: ***Sequestrectomy*** - A **sequestrum** is a piece of dead bone that has become separated from the surrounding healthy bone during necrosis. In the context of **chronic osteomyelitis**, this dead bone acts as a nidus for infection that cannot be eradicated by antibiotics alone. - The presence of a **non-healing sinus** and a sequestrum on X-ray clearly indicates **chronic osteomyelitis**, which requires surgical removal of the infected dead bone (sequestrectomy) for resolution. *Systemic antibiotics* - While systemic antibiotics are crucial in treating acute osteomyelitis and as an adjunct in chronic cases, they are unlikely to cure an infection with a sequestered dead bone. - The **avascular nature of the sequestrum** prevents adequate penetration of antibiotics, making them ineffective as a sole therapy. *Local wound care* - Local wound care might help manage the non-healing sinus superficially but does not address the underlying **bone infection and dead bone**, which is the primary pathology. - This approach would only provide symptomatic relief without resolving the infectious process. *Bone grafting* - Bone grafting is typically performed after the infection has been completely eradicated and involves filling a bone defect. - Performing bone grafting while a **sequestrum and ongoing infection** are present would likely lead to graft failure and continued infection.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free