Mycology — MCQs

Mycology Indian Medical PG Practice Questions and MCQs

Question 71: Black Piedra is caused by which of the following organisms?

A. Pityrosporum orbiculare
B. Exophiala
C. Trichosporon beigelii
D. Piedraia hoae (Correct Answer)

Explanation: **Explanation:** **Black Piedra** is a superficial fungal infection of the hair shaft characterized by the presence of firm, hard, black nodules. The correct answer is **Piedraia hortae** (often referred to in exams as *Piedraia hoae*). This fungus is an ascomycete that produces dark, pigmented hyphae and asci containing ascospores, which cement themselves to the hair shaft, primarily on the scalp. **Analysis of Options:** * **Piedraia hortae (Option D):** The causative agent of Black Piedra. It produces hard, gritty nodules that are firmly attached to the hair. * **Trichosporon beigelii (Option C):** This is the causative agent of **White Piedra**. Unlike Black Piedra, the nodules are soft, white-to-light brown, and easily detached. It typically affects axillary, pubic, and facial hair. * **Pityrosporum orbiculare (Option A):** Also known as *Malassezia furfur*, it causes **Tinea versicolor** (Pityriasis versicolor), characterized by hypo- or hyperpigmented macules on the skin, not hair nodules. * **Exophiala (Option B):** Specifically *Exophiala werneckii* (now *Hortaea werneckii*), is the causative agent of **Tinea nigra**, which presents as dark, brownish-black macules on the palms and soles. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** KOH mount of the hair shows dark hyphae and asci (Black Piedra) or hyaline hyphae and blastoconidia (White Piedra). * **Culture:** *Piedraia hortae* grows slowly on Sabouraud Dextrose Agar (SDA) as greenish-black colonies. * **Treatment:** Shaving or cutting the hair is the most effective treatment; topical antifungals (e.g., ketoconazole) can also be used. * **Mnemonic:** **B**lack = **P**iedraia (Hard/Scalp); **W**hite = **T**richosporon (Soft/Body hair).

Question 72: What is the causative organism in Madura Mycosis Mycetoma?

A. Nocardia (Correct Answer)
B. Dimorphic fungus
C. Aspergillus
D. Dermatophytes

Explanation: **Explanation:** **Mycetoma** (Madura foot) is a chronic, granulomatous infection of the subcutaneous tissue, characterized by a triad of **localized swelling, underlying sinus tracts, and the discharge of grains.** It is etiologically classified into two types: 1. **Actinomycetoma:** Caused by filamentous aerobic bacteria (e.g., *Nocardia*, *Actinomadura*, *Streptomyces*). 2. **Eumycetoma:** Caused by true fungi (e.g., *Madurella mycetomatis*). **Why Option A is Correct:** *Nocardia* species (specifically *N. brasiliensis* and *N. asteroides*) are the most common causes of **Actinomycetoma** worldwide. These are Gram-positive, partially acid-fast, branching filamentous bacteria. In the context of this question, *Nocardia* is the only listed organism that is a primary causative agent of mycetoma. **Why Other Options are Incorrect:** * **B. Dimorphic Fungi:** These cause systemic mycoses (e.g., Histoplasmosis, Sporotrichosis). While *Sporothrix* causes subcutaneous lesions, it does not typically present as a classic Madura foot with grains. * **C. Aspergillus:** This is an opportunistic fungus causing respiratory infections (Aspergilloma) or systemic dissemination, but it is not a causative agent of mycetoma. * **D. Dermatophytes:** These cause superficial fungal infections of the skin, hair, and nails (e.g., Tinea). They do not invade deep subcutaneous tissues to form sinus tracts. **High-Yield Clinical Pearls for NEET-PG:** * **The Grains:** The color of the discharged grains provides a diagnostic clue. *Nocardia* usually produces **yellowish-white** grains, while *Madurella* produces **black** grains. * **Diagnosis:** Crushing the grains and performing a Gram stain or KOH mount is the initial step. * **Treatment:** Actinomycetoma (*Nocardia*) is treated with antibiotics (e.g., **Welsh regimen**: Amikacin + Cotrimoxazole), whereas Eumycetoma requires long-term antifungals and often surgical debridement.

Question 73: A 50-year-old farmer presents with a warty lesion over the left foot. Examination shows warts, cut nodules, and cauliflower-like proliferations. KOH mount shows yeast with dark brown irregular septae. Culture on Sabouraud's agar shows sclerotic bodies. What is the probable diagnosis?

A. Rhinosporidiosis
B. Mycetoma
C. Entomophthoromycosis
D. Chromoblastomycosis (Correct Answer)

Explanation: ### Explanation **1. Why Chromoblastomycosis is correct:** The clinical presentation and laboratory findings are pathognomonic for **Chromoblastomycosis**, a chronic fungal infection of the subcutaneous tissue. * **Clinical Clues:** It typically affects farmers (trauma-related inoculation) and presents as slow-growing, **warty (verrucous)**, or **cauliflower-like** lesions, usually on the lower limbs. * **Microscopic Clues:** The presence of **Sclerotic bodies** (also known as Medlar bodies, "copper pennies," or Muriform bodies) is the gold standard for diagnosis. These are thick-walled, dark brown, multiseptate fungal cells that divide by binary fission rather than budding. They are produced by dematiaceous (pigmented) fungi like *Fonsecaea pedrosoi* and *Phialophora verrucosa*. **2. Why other options are incorrect:** * **Rhinosporidiosis:** Caused by *Rhinosporidium seeberi*, it typically presents as friable, leafy vascular polyps in the nose or nasopharynx. Histology shows large **sporangia** containing thousands of endospores. * **Mycetoma:** Characterized by a triad of tumefaction (swelling), draining sinuses, and the presence of **grains** (sulfur granules). It does not show sclerotic bodies. * **Entomophthoromycosis:** A subcutaneous zygomycosis presenting as firm, painless, non-pitting edema (usually facial or limb). Histology shows thin-walled hyphae surrounded by an eosinophilic Splendore-Hoeppli phenomenon. **3. High-Yield Clinical Pearls for NEET-PG:** * **Sclerotic Bodies:** Pathognomonic for Chromoblastomycosis; they represent a diagnostic "copper penny" appearance. * **Dematiaceous Fungi:** These fungi produce melanin in their cell walls, giving them a natural brown/black color. * **Treatment:** It is notoriously difficult to treat; **Itraconazole** and Terbinafine are the drugs of choice, often combined with surgery or cryotherapy.

Question 74: What is the medical term for ringworm of the nail beds?

A. Tinea capitis
B. Tinea pedis
C. Tinea corporis
D. Tinea unguium (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Tinea unguium** **Medical Concept:** Tinea infections, commonly known as "ringworm," are superficial fungal infections caused by dermatophytes (*Trichophyton*, *Microsporum*, and *Epidermophyton*). These fungi metabolize keratin. The nomenclature of tinea is based on the **anatomical site** of infection. The Latin term **"unguium"** refers to the nails. Therefore, **Tinea unguium** is the clinical term for a dermatophyte infection of the nail plate and nail bed. It is often used interchangeably with "onychomycosis," though the latter also includes non-dermatophyte and yeast infections. **Analysis of Incorrect Options:** * **A. Tinea capitis:** Refers to infection of the **scalp** and hair shafts. It is most common in children and can present as "black dot" alopecia or inflammatory kerion. * **B. Tinea pedis:** Also known as **"Athlete’s foot,"** this affects the feet, particularly the interdigital spaces and soles. * **C. Tinea corporis:** Refers to infection of the **glabrous (hairless) skin** of the trunk and extremities, typically presenting as annular (ring-shaped) lesions with central clearing. **High-Yield Clinical Pearls for NEET-PG:** * **Most common causative agent:** *Trichophyton rubrum* is the most frequent cause of Tinea unguium and Tinea pedis. * **Clinical Subtypes:** The most common form of Tinea unguium is **Distal Lateral Subungual Onychomycosis (DLSO)**. * **Diagnosis:** The gold standard for initial screening is **KOH mount** (showing septate hyphae), while fungal culture on **Sabouraud Dextrose Agar (SDA)** is used for definitive identification. * **Treatment:** Unlike other tinea infections, Tinea unguium requires **systemic antifungal therapy** (e.g., Oral Terbinafine) because topical agents cannot effectively penetrate the nail plate.

Question 75: Asteroid bodies are seen in which of the following conditions?

A. Cryptococcosis
B. Histoplasmosis
C. Sporotrichosis (Correct Answer)
D. Aspergillosis

Explanation: **Explanation:** **Sporotrichosis** is the correct answer. Asteroid bodies (specifically the **Splendore-Hoeppli phenomenon**) are a characteristic histopathological feature of Sporotrichosis, caused by the dimorphic fungus *Sporothrix schenckii*. These bodies consist of a central fungal yeast cell surrounded by a radiating, eosinophilic "star-like" halo of antigen-antibody complexes and host proteins. While not pathognomonic (as they can rarely appear in other granulomatous conditions), they are a classic high-yield association for *Sporothrix* in medical exams. **Analysis of Incorrect Options:** * **A. Cryptococcosis:** Characterized by thick **polysaccharide capsules** visualized with India Ink. Histopathology typically shows "soap bubble" lesions in the brain. * **B. Histoplasmosis:** Characterized by small, intracellular yeast cells found within **macrophages**. It does not typically form asteroid bodies. * **C. Aspergillosis:** Characterized by **septate hyphae with acute-angle (45°) branching**. In allergic forms (ABPA), Curschmann’s spirals or Charcot-Leyden crystals may be seen, but not asteroid bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Sporotrichosis** is often called **"Rose Gardener’s Disease"** due to traumatic inoculation from thorns or sphagnum moss. * **Clinical Presentation:** Presents as a linear chain of nodules along lymphatic drainage (nodular lymphangitis). * **Morphology:** At 25°C (Mold), it shows a **"Flower-like" or "Daisy petal"** arrangement of conidia. At 37°C (Yeast), it shows **"Cigar-shaped"** bodies. * **Treatment:** Drug of choice is **Itraconazole**. Historically, saturated solution of potassium iodide (SSKI) was used.

Question 76: Desert rheumatism is caused by which of the following fungi?

A. Coccidioides (Correct Answer)
B. Paracoccidioides
C. Blastomyces
D. Histoplasma

Explanation: **Explanation:** **Coccidioidomycosis**, caused by the dimorphic fungus *Coccidioides immitis* or *C. posadasii*, is endemic to the arid regions of the Southwestern United States (San Joaquin Valley) and Mexico. The term **"Desert Rheumatism"** refers to a specific clinical triad seen in the primary pulmonary form of the disease, consisting of **fever, joint pains (arthralgia), and erythema nodosum.** It is also known as "Valley Fever." **Why other options are incorrect:** * **Paracoccidioides:** Causes South American Blastomycosis. It is characterized by the "pilot’s wheel" appearance on microscopy and typically presents with painful oral mucosal ulcers and lymphadenopathy. * **Blastomyces:** Causes North American Blastomycosis. It is associated with "Broad-Based Budding" yeast and primarily affects the lungs, skin, and bones, but does not present as the "Desert Rheumatism" complex. * **Histoplasma:** Causes "Darling’s Disease" or Spelunker’s lung. It is associated with bird or bat droppings and is characterized by intracellular yeasts within macrophages. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** *Coccidioides* is unique among dimorphic fungi because it forms **spherules filled with endospores** in tissue (at 37°C) rather than yeast cells. * **Infective form:** Arthroconidia (found in soil/culture). * **Diagnosis:** Spherules are visualized using KOH or silver stains. * **Erythema Nodosum:** In the context of Coccidioidomycosis, the development of erythema nodosum is actually a **good prognostic sign**, indicating a strong cell-mediated immune response.

Question 77: A 54-year-old farmer presents with a chronic cough. A chest X-ray reveals a mass lesion with hilar lymphadenopathy. Biopsy of the mass demonstrates multiple, tiny yeast forms within macrophages. What is the most likely diagnosis?

A. Blastomycosis
B. Coccidioidomycosis
C. Histoplasmosis (Correct Answer)
D. Paracoccidioidomycosis

Explanation: **Explanation:** The clinical presentation and histopathology point directly to **Histoplasmosis**, caused by the dimorphic fungus *Histoplasma capsulatum*. **Why Histoplasmosis is correct:** The hallmark of *Histoplasma* infection is the presence of **small, oval yeast cells (2–4 µm) found within macrophages** (intracellular). In the lungs, these yeasts are phagocytosed by alveolar macrophages but survive and multiply within them. The clinical scenario of a farmer (exposure to soil enriched with bird or bat droppings) presenting with a chronic cough and a mass lesion mimicking bronchogenic carcinoma (the "pseudotumor" presentation) is a classic NEET-PG favorite. **Why other options are incorrect:** * **Blastomycosis:** Characterized by large, **broad-based budding yeasts** with thick, doubly refractile walls. They are typically extracellular and much larger than *Histoplasma*. * **Coccidioidomycosis:** Identified by large **spherules (20–100 µm) filled with endospores**. It is not seen as tiny yeasts within macrophages. * **Paracoccidioidomycosis:** Characterized by large yeasts with multiple buds, resembling a **"Pilot’s wheel"** or "Mickey Mouse" appearance. **High-Yield Clinical Pearls for NEET-PG:** * **Habitat:** Soil contaminated with bird (starlings) or bat droppings (caving/spelunking). * **Stains:** Best visualized with **Gomori Methenamine Silver (GMS)** or PAS stain. * **Key Feature:** It is the only systemic mycosis that is an **obligate intracellular** pathogen of the reticuloendothelial system. * **Differential:** Often mimics Tuberculosis (hilar lymphadenopathy, granulomas) or Sarcoidosis.

Question 78: Which of the following is NOT true regarding cryptococcal infection?

A. Occurs in immunodeficient states.
B. Capsular antigen in CSF is a rapid method of detection.
C. Anticapsular antibody is protective. (Correct Answer)
D. Urease positive.

Explanation: **Explanation:** **Cryptococcus neoformans** is an encapsulated yeast that primarily causes meningitis in humans. Understanding its pathogenesis and diagnostic markers is crucial for NEET-PG. **Why Option C is the correct answer (The "False" statement):** While *Cryptococcus* possesses a prominent polysaccharide capsule (Glucuronoxylomannan), the **anticapsular antibodies are NOT protective**. Immunity against Cryptococcus is primarily **cell-mediated (T-cell driven)**. In fact, high titers of capsular antigen in the blood or CSF actually suppress the immune response rather than stimulating a protective one. This is why the infection is so prevalent in patients with impaired T-cell immunity (e.g., HIV/AIDS). **Analysis of Incorrect Options (True statements):** * **Option A:** It is a classic **opportunistic infection**. It occurs predominantly in immunodeficient states, especially in patients with CD4 counts <100 cells/µL. * **Option B:** Detection of the **Capsular Antigen (CrAg)** via Latex Agglutination or Lateral Flow Assay (LFA) in the CSF is the gold standard for rapid diagnosis, boasting sensitivity and specificity >90%. * **Option D:** *Cryptococcus* species are characteristically **Urease positive**. This biochemical property helps differentiate them from other yeasts like *Candida albicans* (which is urease negative). **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Round, budding yeast with a wide halo on **India Ink** preparation (negative staining). * **Culture:** Grows on Sabouraud Dextrose Agar (SDA) as mucoid, cream-colored colonies. On **Niger Seed/Bird Seed Agar**, it produces brownish-black colonies due to **phenoloxidase** activity (melanin production). * **Pathology:** Causes "Soap bubble appearance" lesions in the brain parenchyma. * **Treatment:** Induction with Amphotericin B + Flucytosine, followed by maintenance with Fluconazole.

Question 79: Which of the following structures are characteristically seen in chromoblastomycosis?

A. Asteroid bodies
B. Sclerotic bodies (Correct Answer)
C. Torres bodies
D. Guameri bodies

Explanation: **Explanation:** **Chromoblastomycosis** is a chronic subcutaneous mycosis caused by dematiaceous (pigmented) fungi, most commonly *Fonsecaea pedrosoi*. **Why Sclerotic Bodies are the Correct Answer:** The hallmark histological feature of chromoblastomycosis is the presence of **Sclerotic bodies** (also known as **Medlar bodies** or "copper-penny" bodies). These are thick-walled, dark brown, globe-shaped fungal cells that divide by binary fission (septation) rather than budding. Their presence in skin scrapings (KOH mount) or histopathology is pathognomonic for the disease. **Analysis of Incorrect Options:** * **Asteroid bodies:** These are eosinophilic radiations seen around fungal elements (Splendore-Hoeppli phenomenon), most characteristically associated with **Sporotrichosis**. * **Torres bodies:** These are intranuclear inclusion bodies seen in hepatocytes in cases of **Yellow Fever**. * **Guarnieri bodies:** These are eosinophilic cytoplasmic inclusion bodies found in cells infected with **Variola (Smallpox)** or Vaccinia virus. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Typically presents as slow-growing, "cauliflower-like" verrucous (warty) lesions, usually on the lower limbs of agricultural workers following traumatic inoculation. * **Key Histology:** Look for **pseudoepitheliomatous hyperplasia** and the characteristic pigmented sclerotic bodies. * **Treatment:** It is notoriously difficult to treat; **Itraconazole** or Terbinafine are the drugs of choice, often combined with surgical excision or cryotherapy.

Question 80: Which one of the following is the geophilic dermatophyte?

A. Microsporum equinum (Correct Answer)
B. Microsporum gypseum
C. Microsporum persicolor
D. Microsporum canis

Explanation: **Explanation:** Dermatophytes are fungi that require keratin for growth and are classified into three groups based on their natural habitat: **Geophilic** (soil), **Zoophilic** (animals), and **Anthropophilic** (humans). **Correct Answer: A. Microsporum gypseum** *(Note: There appears to be a discrepancy in the provided key. In standard medical microbiology, **Microsporum gypseum** is the classic, most frequently cited example of a **geophilic** dermatophyte. It resides in the soil and occasionally causes inflammatory tinea infections in humans who come into contact with contaminated earth.)* **Analysis of Options:** * **Microsporum gypseum (Option B):** The prototypical **Geophilic** species. It produces abundant, symmetrical, thin-walled macroconidia with rounded ends. * **Microsporum canis (Option D):** A **Zoophilic** dermatophyte. Its primary reservoir is cats and dogs; it is a common cause of Tinea capitis in children. * **Microsporum equinum (Option A):** A **Zoophilic** dermatophyte. As the name suggests, its primary host is horses. * **Microsporum persicolor (Option C):** A **Zoophilic** dermatophyte, typically associated with voles and other small wild rodents. **High-Yield Clinical Pearls for NEET-PG:** 1. **Classification by Habitat:** * **Geophilic:** *M. gypseum*, *M. fulvum*. (Cause intense inflammation in humans). * **Zoophilic:** *M. canis* (dogs/cats), *T. verrucosum* (cattle), *T. mentagrophytes* (rodents), *M. equinum* (horses). * **Anthropophilic:** *T. rubrum* (most common worldwide), *T. tonsurans*, *E. floccosum*. 2. **Wood’s Lamp Examination:** *Microsporum* species typically show a **bright green fluorescence** (except *M. gypseum*, which may be dull or negative). 3. **Morphology:** *Microsporum* is characterized by predominant **macroconidia**, whereas *Trichophyton* is characterized by predominant **microconidia**.

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Aspergillosis

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Cryptococcosis

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Zygomycosis

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Endemic Mycoses

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Opportunistic Fungal Infections

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Mycology — MCQs

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