Fungal Skin Infections — MCQs

Fungal Skin Infections Indian Medical PG Practice Questions and MCQs

Question 141: A farmer has an ulcer on leg with indurated margin and multiple sinuses with discharging granules. The likely diagnosis is -

A. Lupus vulgaris
B. Actinomycosis
C. Scrofuloderma
D. Mycetoma (Correct Answer)

Explanation: ***Mycetoma*** - This is the **correct diagnosis** characterized by the classic triad: **tumefaction** (swelling with indurated margin), multiple **draining sinuses**, and discharge of **granules**. - The **occupational history** (farmer with soil exposure) and **location on the leg** are highly suggestive of mycetoma, particularly common in agricultural workers. - The granules are **colonies of microorganisms** (either fungi [eumycetoma] or bacteria [actinomycetoma]) aggregated and encased in a cement-like matrix, a distinctive feature of this chronic infection. - **Key distinguisher**: Mycetoma has a predilection for the **lower extremities**, especially the foot and leg, in individuals with occupational soil exposure. *Actinomycosis* - Actinomycosis is a bacterial infection caused by *Actinomyces* species, which also forms abscesses and draining sinuses with characteristic **"sulfur granules."** - **Why incorrect**: While actinomycosis shares features of sinuses and granules, it most commonly affects the **cervicofacial (50-60%)**, **thoracic**, or **abdominal** regions. - **Leg involvement is rare** for actinomycosis, making mycetoma the more likely diagnosis in this clinical scenario. - The occupational history and typical location favor mycetoma over actinomycosis. *Lupus vulgaris* - This is a form of **cutaneous tuberculosis** presenting as red-brown plaques or nodules, often with an **"apple-jelly" appearance** on diascopy. - While it can cause ulcers, it typically does **not present with deep-seated sinuses and discharging granules**, which are pathognomonic for mycetoma. *Scrofuloderma* - This is a form of cutaneous tuberculosis that develops from the direct extension of underlying **tuberculous adenitis** or **osteomyelitis** to the skin. - It presents as cold abscesses that eventually rupture, forming irregular ulcers and sinuses, but typically **lacks the distinct discharging granules** of mycetoma. - The clinical presentation with granular discharge clearly differentiates mycetoma from scrofuloderma.

Question 142: Tinea "incognito" is due to inappropriate use of systemic and topical:

A. Steroids (Correct Answer)
B. Antibiotics
C. Antivirals
D. Antifungals

Explanation: ***Steroids*** - The use of **topical or systemic steroids** can mask the typical presentation of tinea infections, leading to a modified appearance known as tinea "incognito." - Steroids reduce inflammation and symptoms like itching and redness, but they do not eliminate the fungal infection, often allowing it to spread or become more extensive. *Antibiotics* - Antibiotics are used to treat **bacterial infections** and have no direct effect on fungal organisms that cause tinea. - While inappropriate use of antibiotics can lead to other issues, it does not cause the characteristic presentation of tinea incognito. *Antivirals* - Antivirals are specifically used for **viral infections** and are ineffective against fungal pathogens. - Their use would not lead to the altered clinical presentation of a tinea infection. *Antifungals* - Antifungals are the direct treatment for tinea infections; however, their **inappropriate or insufficient use** might lead to treatment failure or resistance, but not the "incognito" appearance. - Tinea incognito specifically arises when inflammatory agents like steroids suppress visible signs without eradicating the fungus.

Question 143: A child of 7-8 years of age presents with scalp swelling and alopecia. What is the most appropriate diagnostic investigation?

A. KOH staining of the scrapings (Correct Answer)
B. Blood culture
C. PAS staining
D. Gram staining

Explanation: ***KOH staining of the scrapings*** - This presentation is highly suggestive of **tinea capitis**, a fungal infection of the scalp. **Potassium hydroxide (KOH) staining** of hair and scalp scrapings is the primary diagnostic method to identify fungal elements (hyphae and spores). - KOH dissolves keratinous material, making it easier to visualize the **fungal hyphae or spores** under a microscope. *Blood culture* - **Blood culture** is used to diagnose **systemic infections**, particularly bacterial or fungal infections that have entered the bloodstream. - It is **not indicated** for the initial diagnosis of localized skin and hair infections like tinea capitis. *PAS staining* - **Periodic acid–Schiff (PAS) staining** is primarily used for **histopathological examination** of tissue biopsies to detect fungi or other carbohydrates. - While it can identify fungi in tissue sections, it is **not the first-line diagnostic investigation** for tinea capitis, which typically uses direct microscopic examination of scrapings. *Gram staining* - **Gram staining** is a differential staining technique used to classify **bacteria** based on their cell wall properties (Gram-positive or Gram-negative). - It is **not effective** for identifying fungal organisms, which have different cell wall compositions.

Question 144: 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 145: Blue-green fluorescence on Wood's lamp is seen in –

A. Pityriasis versicolor
B. Erythrasma
C. Tinea capitis due to Microsporum canis (Correct Answer)
D. Vitiligo

Explanation: ***Tinea capitis due to Microsporum canis*** - Certain species of *Microsporum*, including **Microsporum canis**, produce a characteristic **blue-green fluorescence** under a Wood's lamp due to metabolites like **pteridine**. - This fluorescence is a rapid aid in diagnosing **tinea capitis** caused by these specific dermatophytes, differentiating them from other fungal infections. *Pityriasis versicolor* - This superficial fungal infection caused by *Malassezia* species often shows a **yellowish-green or coppery-orange fluorescence** under a Wood's lamp, not blue-green. - The fluorescence is due to the presence of **porphyrin metabolites**. *Erythrasma* - This bacterial infection, caused by *Corynebacterium minutissimum*, exhibits a distinct **coral-pink or red fluorescence** under a Wood's lamp. - The fluorescence is attributed to the presence of **coproporphyrin III**. *Vitiligo* - Vitiligo, a condition of depigmentation, does not cause any specific color fluorescence under a Wood's lamp; rather, it appears as **bright white or bluish-white sharply demarcated patches** due to the complete absence of melanin, which enhances their visibility. - There is no fungal or bacterial metabolic product producing fluorescence in vitiligo lesions.

Question 146: Majocchi granuloma is due to:

A. Microsporum
B. Microsporum gypseum
C. Epidermophyton
D. Trichophyton (Correct Answer)

Explanation: ***Trichophyton*** - **Majocchi granuloma** is a deep fungal infection of the dermis and subcutaneous tissue caused by dermatophytes, most commonly species of the genus **Trichophyton**, such as *Trichophyton rubrum* or *Trichophyton mentagrophytes*. - This infection often occurs when dermatophytes penetrate hair follicles or traumatized skin, leading to a granulomatous inflammatory response. *Microsporum* - While *Microsporum* species are dermatophytes that can cause tinea infections, particularly **tinea capitis** (ringworm of the scalp), they are less commonly implicated in causing **Majocchi granuloma**. - *Microsporum* species primarily infect hair and skin surfaces but rarely cause deep follicular or granulomatous infections. *Microsporum gypseum* - *Microsporum gypseum* is a geophilic dermatophyte that can cause **tinea corporis** and **tinea capitis**. - Similar to other *Microsporum* species, it is not a typical cause of the deeper, granulomatous infection known as **Majocchi granuloma**. *Epidermophyton* - The genus *Epidermophyton*, specifically *Epidermophyton floccosum*, typically causes infections of the skin and nails, such as **tinea cruris** (jock itch) and **tinea pedis** (athlete's foot). - It does not commonly infect hair and is not a known primary causative agent of **Majocchi granuloma**.

Question 147: 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 148: Which of the following is used in the treatment of Pityriasis versicolor?

A. Itraconazole (Correct Answer)
B. Griseofulvin
C. Terbinafine
D. All of the options

Explanation: ***Itraconazole*** - **Itraconazole** is an effective oral antifungal agent commonly used to treat Pityriasis versicolor, particularly in widespread or recurrent cases. - It works by inhibiting fungal cytochrome P450-dependent 14α-lanosterol demethylase, thereby disrupting ergosterol synthesis and fungal cell membrane integrity. - Standard regimen: 200 mg once daily for 5-7 days or 200 mg twice daily for 1 day. *Griseofulvin* - **Griseofulvin** is an oral antifungal primarily used for dermatophyte infections (e.g., tinea capitis, tinea corporis), not Pityriasis versicolor, which is caused by *Malassezia* species (a yeast). - It acts by disrupting fungal mitosis and is concentrated in keratinocytes, but has **no activity against yeasts** like *Malassezia*. *Terbinafine* - **Terbinafine** is an allylamin antifungal that primarily targets dermatophytes by inhibiting squalene epoxidase, an enzyme involved in ergosterol synthesis. - While it has **limited activity** against *Malassezia* species, it is not considered a first-line or preferred systemic treatment for Pityriasis versicolor. - Azoles (itraconazole, fluconazole) are far more effective for this condition. *All of the options* - This option is incorrect because **griseofulvin** has no antifungal activity against *Malassezia* species and **terbinafine** is not a preferred treatment. - Only **itraconazole** among the listed options is an appropriate and effective systemic treatment for Pityriasis versicolor.

Question 149: A 23-year-old female came to a dermatology clinic with the complaints of brittle scalp hair and the presence of firmly adherent, black, gritty, hard nodules along the hair shaft. Pruritus is absent. What is the most probable causative agent?

A. Malassezia furfur
B. Trichosporon beigelii
C. Microsporum canis
D. Piedraia hortae (Correct Answer)

Explanation: ***Piedraia hortae*** - This fungus causes **Black piedra**, characterized by **firmly adherent**, hard, **black nodules** on the hair shaft, leading to brittle hair. - The nodules are formed by fungal hyphae and spores cemented together, which are distinctive clinical feature. *Malassezia furfur* - This yeast is associated with **Tinea versicolor**, characterized by **hypo- or hyperpigmented patches** on the skin, not hard nodules on hair. - It can also cause **dandruff** or seborrheic dermatitis, presenting as scaling of the scalp. *Trichosporon beigelii* - This yeast causes **White piedra**, which involves the formation of **soft**, yellowish-white nodules on the hair shaft. - Unlike Black piedra, the nodules are easily removed and typically found on axillary and pubic hair. *Microsporum canis* - This dermatophyte causes **Tinea capitis**, a fungal infection of the scalp that leads to **scaly patches** and **hair breakage at the root**. - It does not form distinct, hard, black nodules along the hair shaft; rather, it causes scaling and inflammation of the scalp.

Question 150: A child comes with a circular 3cm x 3cm scaly patchy hair loss with itching in the lesions. The investigation of choice is

A. Tzanck smear
B. Gram stain
C. KOH mount (Correct Answer)
D. Split skin smear

Explanation: ***Correct: KOH mount (Potassium Hydroxide mount)*** - A **KOH mount** is the investigation of choice for suspected **dermatophyte infections** (tinea capitis), which commonly present as circular, scaly patches of hair loss with itching in children. - It involves dissolving keratinous material to visualize **fungal hyphae** and spores directly under a microscope. - This is a quick, cost-effective, and highly specific first-line diagnostic test. *Incorrect: Tzanck smear* - A **Tzanck smear** is primarily used to diagnose **viral infections** like herpes simplex or varicella-zoster by identifying multinucleated giant cells. - It is not effective for detecting fungal elements responsible for scaly hair loss. *Incorrect: Gram stain* - A **Gram stain** is a technique used to classify **bacteria** based on their cell wall properties. - It would not reveal fungal hyphae or spores relevant to the described condition. *Incorrect: Split skin smear* - A **split skin smear** (or slit-skin smear) is typically used in the diagnosis of **leprosy** to identify acid-fast bacilli. - This technique involves scraping the dermis and is not suitable for diagnosing superficial fungal infections.

Practice by Chapter

Dermatophytoses

Practice Questions

Tinea Versicolor

Practice Questions

Candidiasis

Practice Questions

Onychomycosis

Practice Questions

Subcutaneous Mycoses

Practice Questions

Systemic Mycoses with Cutaneous Manifestations

Practice Questions

Opportunistic Fungal Infections

Practice Questions

Mycetoma

Practice Questions

Tropical Fungal Infections

Practice Questions

Diagnosis of Fungal Infections

Practice Questions

Antifungal Therapy

Practice Questions

Preventive Strategies

Practice Questions

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