Mycology Practice Questions

Q: 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?

Chromoblastomycosis. ### 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.

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

Sporotrichosis. **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.

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

Coccidioides. **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.

Q: 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?

Histoplasmosis. **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.

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

Anticapsular antibody is protective.. **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 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.

Q: Which of the following Aspergillus species produces black-colored colonies on Sabouraud's dextrose agar?

A. niger. **Explanation:** The correct answer is **B. A. niger**. **Aspergillus niger** is characterized by its rapid growth on Sabouraud’s Dextrose Agar (SDA), initially appearing white but quickly turning into a dense, **carbon-black** color. This pigmentation is due to the production of dark conidia (spores) on the surface of the colony. Microscopically, it features large, globose, black conidial heads with "biseriate" sterigmata covering the entire vesicle. **Analysis of Incorrect Options:** * **A. fumigatus:** This is the most common pathogenic species. It produces **smoky-green** or grayish-green colonies. It is known for its thermotolerance (growing at 45°C) and "uniseriate" phialides. * **C. A. flavus:** This species typically produces **yellowish-green** or lime-green colonies. It is clinically significant for producing **Aflatoxins**, which are linked to hepatocellular carcinoma. * **D. None of the above:** Incorrect, as A. niger is the classic "black mold." **High-Yield Clinical Pearls for NEET-PG:** 1. **Otomycosis:** *A. niger* is the most common cause of fungal otitis externa, often presenting with a "wet newspaper" appearance or black specks in the ear canal. 2. **Oxalate Crystals:** *A. niger* is unique for producing calcium oxalate crystals in tissue or sputum, which can be a diagnostic clue in biopsies. 3. **Aspergilloma:** While *A. fumigatus* is the primary cause of "fungus balls" in pre-existing lung cavities, all three species mentioned can be involved. 4. **Morphology:** Remember the color mnemonic: **F**umigatus (**F**orest/Green), **Fl**avus (**Fl**uorescent/Yellow-Green), **N**iger (**N**ight/Black).

Q: Broad based budding is seen in which of the following fungal infections?

Blastomycosis. ### Explanation **Blastomycosis (*Blastomyces dermatitidis*)** is the correct answer because it is characterized by a unique morphological feature known as **Broad-Based Budding**. In tissue samples (yeast phase), the daughter cell remains attached to the mother cell by a wide neck, making the base of the bud nearly as wide as the cell itself. The yeast cells are typically large (8–15 µm) with thick, "doubly refractile" walls. #### Analysis of Incorrect Options: * **A. Coccidiomycosis:** Does not exist as yeast in tissue. Instead, it forms large **spherules** (20–100 µm) filled with numerous small **endospores**. * **B. Paracoccidiomycosis:** Characterized by multiple narrow-based buds surrounding a central large yeast cell, resembling a **"Pilot’s Wheel"** or **"Mickey Mouse"** appearance. * **C. Cryptococcosis:** This is a monomorphic yeast characterized by **narrow-based budding** and a prominent polysaccharide capsule (visualized with India Ink). #### NEET-PG High-Yield Pearls: * **Blastomycosis Mnemonic:** "B" for **B**lasto, **B**road-based budding, **B**one involvement (common site of dissemination), and **B**ig (large yeast). * **Geographic distribution:** Primarily found in the Ohio and Mississippi River Valleys (similar to Histoplasmosis). * **Dimorphism:** These fungi are "molds in the cold (25°C) and yeasts in the heat (37°C)." * **Histoplasmosis (Comparison):** Shows small, intracellular yeasts within macrophages (no broad budding).

Q: Which of the following statements regarding Candida are true?

Commensal in skin. **Explanation:** *Candida albicans* is a versatile opportunistic fungus. Understanding its ecological niche and clinical presentation is crucial for NEET-PG. **1. Why Option A is Correct:** *Candida* species are part of the **normal human flora (commensals)**. They primarily colonize the gastrointestinal tract (mouth to anus), the female genital tract (vagina), and the **skin**, particularly in moist areas (intertriginous sites). When the host's local or systemic immunity is compromised, these commensals transition into pathogens. **2. Analysis of Incorrect Options:** * **Option B:** While pregnancy predisposes women to **Vulvovaginal Candidiasis** (due to high estrogen levels and increased glycogen content in the vaginal mucosa), **oral candidiasis** is not specifically "common" in pregnancy; it is more characteristic of T-cell deficiencies or inhaled steroid use. * **Option C:** In HIV/AIDS patients, *Candida* infections follow a specific hierarchy. **Oropharyngeal Candidiasis** (Thrush) occurs at a relatively early stage (CD4 count <500 cells/mm³), but **Esophageal Candidiasis** is an AIDS-defining illness occurring at a later, more advanced stage (CD4 <200 cells/mm³). * **Option D:** While *Candida* can be visualized on a Gram stain (appearing as large, Gram-positive budding yeast cells), the statement is technically less definitive as a "characteristic" compared to its commensal nature. However, in many exam contexts, Option A is the established physiological fact. **High-Yield Clinical Pearls:** * **Morphology:** *Candida* is dimorphic; it forms **Pseudohyphae** in tissues, but *C. albicans* specifically produces **Germ Tubes** (Reynolds-Braude phenomenon) when incubated in serum at 37°C. * **Culture:** Grows on **Sabouraud Dextrose Agar (SDA)** as creamy white, smooth colonies with a "yeasty" odor. * **Chlamydospores:** *C. albicans* produces thick-walled terminal chlamydospores on Cornmeal Agar.

Q: A 34-week pregnant female presented with intense itching over the vulvar area and a white, cheesy vaginal discharge. On examination, vulvar erythema is noted. Which among the following is the causative organism in this patient?

Candida albicans. **Explanation:** The clinical presentation of **intense vulvar itching (pruritus)** and a **thick, white, "curdy" or "cheesy" vaginal discharge** is classic for **Vulvovaginal Candidiasis (VVC)**. In this case, the patient’s pregnancy (34 weeks) is a significant predisposing factor. High estrogen levels during pregnancy increase the glycogen content of the vaginal mucosa, providing an ideal environment for the overgrowth of *Candida*. **Why Candida albicans is correct:** * **Causative Agent:** *Candida albicans* is responsible for 80–90% of fungal vaginal infections. * **Clinical Features:** Characterized by "cottage-cheese" like discharge, vulvar erythema, edema, and intense itching. * **Diagnosis:** On microscopy (KOH mount), it shows pseudohyphae and budding yeast cells. The vaginal pH is typically **normal (<4.5)**, which helps distinguish it from Trichomoniasis or Bacterial Vaginosis. **Why other options are incorrect:** * **Epidermophyton & Tinea:** These are dermatophytes responsible for fungal infections of the skin (like Tinea cruris/jock itch). While they cause itching in the groin, they do not cause vaginal discharge. * **Aspergillus:** This is a filamentous fungus that typically causes respiratory infections or systemic opportunistic infections; it is not a standard cause of vaginitis. **NEET-PG High-Yield Pearls:** * **Risk Factors:** Pregnancy, Diabetes Mellitus, recent antibiotic use, and immunosuppression. * **Drug of Choice (Non-pregnant):** Oral Fluconazole (150 mg single dose). * **Drug of Choice (Pregnancy):** **Topical Azoles** (e.g., Clotrimazole) for 7 days are preferred; oral fluconazole is generally avoided in pregnancy. * **Gold Standard Diagnosis:** Culture on **Sabouraud’s Dextrose Agar (SDA)**.

Q: Which of the following is not an opportunistic infection in AIDS?

Dermatophyte. **Explanation:** In the context of HIV/AIDS, **opportunistic infections (OIs)** are defined as infections that occur more frequently or are more severe in individuals with weakened immune systems (specifically when CD4+ T-cell counts drop). **Why Dermatophytes are the correct answer:** Dermatophytes (e.g., *Trichophyton*, *Microsporum*, and *Epidermophyton*) are **superficial mycoses** that infect keratinized tissues like skin, hair, and nails. While they can occur in AIDS patients, they are not classified as "opportunistic infections" because they commonly affect immunocompetent individuals and do not cause life-threatening systemic disease even in the presence of severe immunosuppression. In AIDS patients, dermatophytoses may present more extensively or atypically, but they remain localized to the integumentary system. **Analysis of Incorrect Options:** * **Cryptococcus neoformans:** A major OI in AIDS (usually when CD4 <100 cells/mm³). It is the most common cause of fungal meningitis in these patients. * **Aspergillosis:** While more common in neutropenic patients, *Aspergillus* species act as opportunistic pathogens in advanced AIDS, causing invasive pulmonary disease. * **Pneumocystis jirovecii:** Historically the most common defining OI in AIDS. It causes *Pneumocystis* pneumonia (PCP) typically when CD4 counts fall below 200 cells/mm³. **High-Yield Clinical Pearls for NEET-PG:** * **CD4 <200:** Threshold for *Pneumocystis jirovecii* prophylaxis (Trimethoprim-Sulfamethoxazole). * **CD4 <100:** Threshold for *Cryptococcus* and *Toxoplasma* risk. * **Diagnosis:** Cryptococcus is identified via **India Ink** preparation (capsule visualization) or Cryptococcal Antigen (CrAg) test. * **Pneumocystis:** Identified via **Gomori Methenamine Silver (GMS)** stain showing "crushed ping-pong ball" appearance.

Question 1

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?

Accepted Answer

Chromoblastomycosis

Answer

Rhinosporidiosis

Answer

Mycetoma

Answer

Entomophthoromycosis

Question 2

Asteroid bodies are seen in which of the following conditions?

Accepted Answer

Sporotrichosis

Answer

Cryptococcosis

Answer

Histoplasmosis

Answer

Aspergillosis

Question 3

Desert rheumatism is caused by which of the following fungi?

Accepted Answer

Coccidioides

Answer

Paracoccidioides

Answer

Blastomyces

Answer

Histoplasma

Question 4

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?

Accepted Answer

Histoplasmosis

Answer

Blastomycosis

Answer

Coccidioidomycosis

Answer

Paracoccidioidomycosis

Question 5

Which of the following is NOT true regarding cryptococcal infection?

Accepted Answer

Anticapsular antibody is protective.

Answer

Occurs in immunodeficient states.

Answer

Capsular antigen in CSF is a rapid method of detection.

Answer

Urease positive.

Question 6

Which of the following Aspergillus species produces black-colored colonies on Sabouraud's dextrose agar?

Accepted Answer

A. niger

Answer

A. fumigatus

Answer

A. flavus

Answer

None of the above

Question 7

Broad based budding is seen in which of the following fungal infections?

Accepted Answer

Blastomycosis

Answer

Coccidiomycosis

Answer

Paracoccidiomycosis

Answer

Cryptococcosis

Question 8

Which of the following statements regarding Candida are true?

Accepted Answer

Commensal in skin

Answer

Oral candidiasis is common in pregnancy

Answer

In AIDS, it occurs at an early stage

Answer

Gram staining is done

Question 9

A 34-week pregnant female presented with intense itching over the vulvar area and a white, cheesy vaginal discharge. On examination, vulvar erythema is noted. Which among the following is the causative organism in this patient?

Accepted Answer

Candida albicans

Answer

Epidermophyton

Answer

Aspergillus

Answer

Tinea

Question 10

Which of the following is not an opportunistic infection in AIDS?

Accepted Answer

Dermatophyte

Answer

Cryptococcus

Answer

Aspergillosis

Answer

Pneumocystis jirovecii

Mycology — MCQs

Mycology — MCQs

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