Superficial Mycoses — MCQs

10 questions

A 10-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hair, and lymph nodes enlarged in occipital region, which of the following would be most helpful for diagnostic evaluation?

Which of the following is not a part of P. versicolor treatment -

Pityriasis versicolor is caused by which organism?

Wood lamp is used to diagnose –

Best diagnostic test for fungal skin infection –

An 8-year-old child has localized non-cicatricial alopecia over scalp with itching and scales. The diagnosis is :

A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?

Q8Medium

Which statement is false regarding Cryptococcus neoformans?

Q9Easy

Which of the following is a non-culturable fungus?

Q10Easy

Which of the following is a dimorphic fungus?

Superficial Mycoses Indian Medical PG Practice Questions and MCQs

Question 1: A 10-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hair, and lymph nodes enlarged in occipital region, which of the following would be most helpful for diagnostic evaluation?

A. Bacterial culture
B. Biopsy and giemsa staining
C. Patch test, gram staining and Tzank smear
D. KOH mount (Correct Answer)

Explanation: ***KOH mount*** - The symptoms of **painful boggy scalp swelling**, **purulent discharge**, **easily pluckable hair**, and **occipital lymphadenopathy** in a child are highly suggestive of **Tinea capitis**, specifically **Kerion**. - A **KOH mount** is the most direct and rapid method to identify fungal elements (hyphae and spores) in hair shafts and scales, confirming the diagnosis of a dermatophyte infection. *Bacterial culture* - While there is **purulent discharge**, the primary presentation with **boggy swelling** and **hair loss** is more indicative of a fungal etiology. - A bacterial culture would only be useful to rule out secondary bacterial infection, but not as the initial diagnostic step for the described primary fungal condition. *Biopsy and Giemsa staining* - A **biopsy** is an invasive procedure and generally not the first-line diagnostic test for uncomplicated **Tinea capitis/Kerion**, where a non-invasive KOH mount is sufficient. - **Giemsa staining** is primarily used for identifying certain bacteria, parasites, or cellular morphology, but it is not the standard or most efficient method for diagnosing fungal infections of the hair. *Patch test, Gram staining and Tzank smear* - A **patch test** is used to diagnose **allergic contact dermatitis** and is irrelevant to the presented symptoms. - **Gram staining** is for bacterial identification, and a **Tzank smear** is used for viral infections like herpes, neither of which are indicated by the clinical picture of a fungal scalp infection.

Question 2: Which of the following is not a part of P. versicolor treatment -

A. Selenium sulfide
B. Clotrimazole
C. Ketoconazole
D. Griseofulvin (Correct Answer)

Explanation: **Griseofulvin (Correct - NOT used for P. versicolor)** - **Griseofulvin** interferes with fungal cell division and is primarily used for dermatophyte infections of the skin, hair, and nails, not superficial yeast infections like *P. versicolor*. - It is systemically absorbed and incorporated into **keratin precursor cells**, offering protection against dermatophytes in newly formed tissue. - *Malassezia* species (causing P. versicolor) are **yeasts**, not dermatophytes, making griseofulvin ineffective. *Selenium sulfide (Incorrect - IS used)* - **Selenium sulfide** is an effective topical antifungal agent commonly used in shampoos and lotions to treat *P. versicolor* by inhibiting the growth of *Malassezia* species. - It works by reducing **sebum production** and having a direct fungistatic effect on the yeast. *Clotrimazole (Incorrect - IS used)* - **Clotrimazole** is a broad-spectrum azole antifungal that is very effective as a topical treatment for *P. versicolor* by inhibiting ergosterol synthesis in the fungal cell membrane. - It works well for localized patches of the infection. *Ketoconazole (Incorrect - IS used)* - **Ketoconazole**, another azole antifungal, is highly effective for *P. versicolor* and can be used topically (shampoos, creams) or orally in more extensive or recalcitrant cases. - It disrupts the fungal cell membrane by inhibiting the synthesis of **ergosterol**.

Question 3: Pityriasis versicolor is caused by which organism?

A. E. floccosum
B. M. gypseum
C. M. furfur (Correct Answer)
D. T. tonsurans

Explanation: ***M. furfur*** - **Pityriasis versicolor** is caused by **Malassezia furfur** (also known as Pityrosporum ovale), a dimorphic yeast that is a normal inhabitant of human skin. - Under certain conditions (e.g., humidity, excessive sweating), it overgrows, leading to characteristic hypopigmented or hyperpigmented patches. *E. floccosum* - **Epidermophyton floccosum** is a dermatophyte known to cause **tinea pedis (athlete's foot)**, tinea cruris (jock itch), and tinea unguium (nail infections). - It does not cause pityriasis versicolor, which is a superficial yeast infection, not a dermatophyte infection. *M. gypseum* - **Microsporum gypseum** is a geophilic dermatophyte, meaning it is found in soil and can cause **tinea corporis** or **tinea capitis** in humans, often through contact with contaminated soil. - It is not associated with pityriasis versicolor. *T. tonsurans* - **Trichophyton tonsurans** is an anthropophilic dermatophyte, a common cause of **tinea capitis** (ringworm of the scalp) and sometimes tinea corporis, particularly in children. - It causes specific types of dermatophytosis and is not the causative agent of pityriasis versicolor.

Question 4: Wood lamp is used to diagnose –

A. Erysipelas
B. Pityriasis rosea
C. Psoriasis
D. Tinea versicolor (Correct Answer)

Explanation: ***Tinea versicolor*** - A Wood lamp is used to diagnose **tinea versicolor** by revealing a characteristic **yellow-green fluorescence** of the affected areas due to the production of **porphyrins** by the causative yeast, *Malassezia*. - This specific fluorescence helps differentiate **tinea versicolor** from other skin conditions that may have a similar appearance. *Erysipelas* - **Erysipelas** is a superficial bacterial skin infection, typically diagnosed based on its **clinical presentation** of a rapidly spreading, fiery red, tender, and sharply demarcated rash. - A Wood lamp is **not used** in the diagnosis of erysipelas, as it does not cause any specific fluorescence under UV light. *Pityriasis rosea* - **Pityriasis rosea** is a self-limiting inflammatory skin rash, usually diagnosed clinically by its distinctive morphology, including a **herald patch** followed by smaller, oval, fawn-colored lesions in a "Christmas tree" pattern. - A Wood lamp examination would **not show any specific fluorescence** indicative of pityriasis rosea. *Psoriasis* - **Psoriasis** is a chronic autoimmune skin condition characterized by well-demarcated, erythematous plaques covered with silvery scales, typically diagnosed through **clinical examination** and sometimes a skin biopsy. - A Wood lamp is **not a diagnostic tool** for psoriasis, as psoriatic lesions do not fluoresce in a characteristic manner under UV light.

Question 5: Best diagnostic test for fungal skin infection –

A. KOH test (Correct Answer)
B. Diascopy
C. Patch test
D. Wood's lamp

Explanation: ***Correct: KOH test*** - The **potassium hydroxide (KOH) test** is the **most common and rapid method** for diagnosing dermatophyte infections. - It involves dissolving keratinous material to visualize **fungal hyphae** and **spores** under a microscope. - KOH test is **quick, inexpensive, and can be performed in any outpatient setting**, making it the best first-line diagnostic test. *Incorrect: Diascopy* - **Diascopy** is used to determine if a lesion is **vascular** (erythematous and blanches) or **non-vascular** (purpuric and does not blanch). - It involves pressing a glass slide against the lesion and observing color changes. - This test is not relevant for fungal identification. *Incorrect: Patch test* - A **patch test** is used to identify **allergic contact dermatitis** by applying specific allergens to the skin and observing for a delayed hypersensitivity reaction. - It is not designed to detect or diagnose fungal infections. *Incorrect: Wood's lamp* - A **Wood's lamp** emits ultraviolet light and is used to detect certain skin conditions that fluoresce. - While it can help diagnose some fungal infections like **Tinea capitis** caused by *Microsporum* species (which fluoresces green), it is **not a definitive diagnostic test** for all fungal infections. - Many common dermatophytes do not fluoresce, leading to false negatives.

Question 6: An 8-year-old child has localized non-cicatricial alopecia over scalp with itching and scales. The diagnosis is :

A. Lichen planus
B. Tinea Capitis (Correct Answer)
C. Tinea Barbae
D. Alopecia areata

Explanation: ***Tinea Capitis*** - **Tinea capitis** typically presents as **localized, non-cicatricial alopecia** with features like **scaling**, **itching**, and broken hairs, which are consistent with the child's symptoms. - It's a common **dermatophyte infection** of the scalp, particularly in children, caused by fungi like *Trichophyton* or *Microsporum*. *Lichen planus* - **Lichen planus** can cause alopecia, but it is typically a **cicatricial (scarring)** alopecia, unlike the non-cicatricial finding described. - It is more commonly associated with **purplish, polygonal, pruritic papules** on the skin and mucous membranes. *Tinea Barbae* - **Tinea barbae** specifically affects the **beard and mustache area** in adult males and would not present as alopecia on the scalp in an 8-year-old child. - It usually involves deep follicular inflammation with **pustules and nodules**. *Alopecia areata* - **Alopecia areata** is characterized by **smooth, circular patches of non-scarring hair loss** without associated scaling or significant itching. - The presence of **scaling and itching** in this case makes alopecia areata less likely.

Question 7: A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?

A. Tzanck smear
B. KOH mount (Correct Answer)
C. Woods lamp
D. Biopsy

Explanation: ***KOH mount*** - A **KOH mount** (potassium hydroxide) dissolves keratinocytes, allowing for direct visualization of fungal elements such as **hyphae** and **spores** under a microscope. This is the **most rapid and cost-effective test** for confirming fungal infections like **onychomycosis**. - The patient's presentation with **yellowish discoloration** and **"tunneling"** of nails (suggesting onycholysis and subungual hyperkeratosis), along with a history of recurrent groin itching (potentially **tinea cruris**), strongly points to a fungal infection. *Tzanck smear* - A **Tzanck smear** is primarily used to detect multinucleated giant cells in **herpesvirus infections** (e.g., herpes simplex, varicella-zoster). - It is not useful for identifying fungal elements responsible for nail discoloration or suspected onychomycosis. *Woods lamp* - A **Woods lamp** uses ultraviolet light to detect specific fluorescent substances, particularly useful for diagnosing certain **bacterial infections** (e.g., *Corynebacterium minutissimum* in erythrasma) or some **tinea capitis** species (*Microsporum*). - Most common dermatophytes causing onychomycosis **do not fluoresce** under a Wood's lamp, making it an unreliable diagnostic tool in this scenario. *Biopsy* - A **nail biopsy** (with histology and special stains like PAS) is a highly accurate diagnostic method for onychomycosis, especially when other tests are inconclusive. - However, it is an **invasive procedure**, takes more time for results, and is generally not the **most rapid** initial test compared to a KOH mount.

Question 8: Which statement is false regarding Cryptococcus neoformans?

A. Grows at 5°C and 37°C
B. Has 4 serotypes
C. Urease negative (Correct Answer)
D. Causes superficial skin infection

Explanation: **Explanation:** *Cryptococcus neoformans* is an encapsulated yeast primarily associated with pigeon droppings and is a significant opportunistic pathogen in immunocompromised patients (e.g., HIV/AIDS). **1. Why "Urease negative" is the False Statement:** *Cryptococcus neoformans* is characteristically **Urease positive**. The production of the urease enzyme is a key biochemical marker used in the laboratory to differentiate it from other yeasts like *Candida albicans* (which is urease negative). It hydrolyzes urea to produce ammonia, raising the pH and changing the indicator color. **2. Analysis of Other Options:** * **Option A (Grows at 5°C and 37°C):** This is true. Unlike many other pathogenic fungi, *C. neoformans* can grow at 37°C (essential for human pathogenicity) and also at lower temperatures like 4°C–5°C. * **Option B (Has 4 serotypes):** This is true. Based on capsular polysaccharide antigens, it is classified into four serotypes: **A, B, C, and D**. (Note: Serotype A is *C. neoformans var. grubii*, while B and C are now often classified as *C. gattii*). * **Option D (Causes superficial skin infection):** This is true. While meningitis is the most common presentation, primary or secondary cutaneous cryptococcosis can occur, presenting as papules, pustules, or ulcerations. **High-Yield Clinical Pearls for NEET-PG:** * **Virulence Factor:** The **Polysaccharide capsule** (Glucuronoxylomannan) is the most important; it inhibits phagocytosis. * **Staining:** **India Ink** preparation shows a "halo" (negative staining). **Mucicarmine** stains the capsule red. * **Culture:** Grows on **Bird Seed Agar** (Niger Seed Agar) producing brown/black colonies due to **Phenoloxidase** activity (melanin production). * **Drug of Choice:** Induction with Amphotericin B + Flucytosine, followed by Fluconazole.

Question 9: Which of the following is a non-culturable fungus?

A. Rhinosporidium (Correct Answer)
B. Candida
C. Sporothrix
D. Penicillium

Explanation: **Explanation:** The correct answer is **Rhinosporidium seeberi**. This organism is unique in medical mycology because it has **never been successfully cultured** on artificial laboratory media (like SDA) or in cell culture. Its classification was historically debated, but molecular analysis (18S rRNA sequencing) has placed it among the *Mesomycetozoea*, a group of aquatic fish parasites, though it is still traditionally studied in Mycology. **Why the other options are incorrect:** * **Candida:** A common yeast that grows readily on Sabouraud Dextrose Agar (SDA) within 24–48 hours, forming creamy white colonies. * **Sporothrix:** A dimorphic fungus that can be cultured at 25°C (mold form with "flower-like" sporulation) and 37°C (yeast form). * **Penicillium:** A common saprophytic mold that grows rapidly in culture, characterized by its "brush-like" conidiophores. **High-Yield Clinical Pearls for NEET-PG:** * **Disease:** Rhinosporidiosis typically presents as **friable, leafy, strawberry-like polypoid masses** in the nose or nasopharynx. * **Transmission:** Associated with bathing in stagnant freshwater (ponds/tanks). * **Diagnosis:** Since it cannot be cultured, diagnosis relies on **histopathology**. Look for large **sporangia** (up to 350 µm) containing thousands of **endospores**. * **Treatment:** Surgical excision with wide-base cauterization is the treatment of choice; medical therapy (Dapsone) has limited efficacy.

Question 10: Which of the following is a dimorphic fungus?

A. Candida
B. Histoplasma (Correct Answer)
C. Rhizopus
D. Mucor

Explanation: ### Explanation **Correct Answer: B. Histoplasma** **Concept of Dimorphism:** Dimorphic fungi are organisms that exist in two distinct morphological forms depending on environmental conditions (primarily temperature). They exist as **molds (hyphae)** in the environment/soil at 25°C and as **yeasts** in the human host tissues at 37°C. A common mnemonic to remember this is: *"Mold in the Cold, Yeast in the Beast."* **Histoplasma capsulatum** is a classic systemic dimorphic fungus. In the body, it is typically found as small, intracellular yeasts within macrophages. **Analysis of Incorrect Options:** * **A. Candida:** While *Candida albicans* is often called "polymorphic" because it forms yeast, pseudohyphae, and true hyphae (germ tubes), it is **not** classified as a true thermal dimorphic fungus. Interestingly, it reverses the rule: it forms hyphae/germ tubes at 37°C (body temperature). * **C & D. Rhizopus and Mucor:** These belong to the class Zygomycetes. They are **monomorphic molds** characterized by broad, non-septate hyphae with right-angle branching. They do not have a yeast phase. **High-Yield NEET-PG Pearls:** 1. **List of Dimorphic Fungi:** *Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Sporothrix schenckii,* and *Talaromyces (Penicillium) marneffei.* 2. **Histoplasma Clue:** Look for a history of exposure to **bird or bat droppings** (guano) in caves or chicken coops. 3. **Diagnosis:** On Giemsa or Wright stain, Histoplasma appears as small oval yeasts with a narrow base of budding, often seen inside **macrophages**. 4. **Coccidioides Exception:** It is dimorphic but forms **spherules** filled with endospores in the tissue, rather than simple yeast cells.

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