Fungal Skin Infections Practice Questions

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

Steroids. ***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.

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

KOH staining of the scrapings. ***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.

Q: Best diagnostic test for fungal skin infection –

KOH test. ***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.

Q: Blue-green fluorescence on Wood's lamp is seen in –

Tinea capitis due to Microsporum canis. ***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.

Q: Majocchi granuloma is due to:

Trichophyton. ***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**.

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

Griseofulvin. **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**.

Q: Which of the following is used in the treatment of Pityriasis versicolor?

Itraconazole. ***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.

Q: 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?

Piedraia hortae. ***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.

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

KOH mount. ***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.

Question 1

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

Accepted Answer

Mycetoma

Answer

Lupus vulgaris

Answer

Actinomycosis

Answer

Scrofuloderma

Question 2

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

Accepted Answer

Steroids

Answer

Antibiotics

Answer

Antivirals

Answer

Antifungals

Question 3

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

Accepted Answer

KOH staining of the scrapings

Answer

Blood culture

Answer

PAS staining

Answer

Gram staining

Question 4

Best diagnostic test for fungal skin infection –

Accepted Answer

KOH test

Answer

Diascopy

Answer

Patch test

Answer

Wood's lamp

Question 5

Blue-green fluorescence on Wood's lamp is seen in –

Accepted Answer

Tinea capitis due to Microsporum canis

Answer

Pityriasis versicolor

Answer

Erythrasma

Answer

Vitiligo

Question 6

Majocchi granuloma is due to:

Accepted Answer

Trichophyton

Answer

Microsporum

Answer

Microsporum gypseum

Answer

Epidermophyton

Question 7

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

Accepted Answer

Griseofulvin

Answer

Selenium sulfide

Answer

Clotrimazole

Answer

Ketoconazole

Question 8

Which of the following is used in the treatment of Pityriasis versicolor?

Accepted Answer

Itraconazole

Answer

Griseofulvin

Answer

Terbinafine

Answer

All of the options

Question 9

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?

Accepted Answer

Piedraia hortae

Answer

Malassezia furfur

Answer

Trichosporon beigelii

Answer

Microsporum canis

Question 10

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

Accepted Answer

KOH mount

Answer

Tzanck smear

Answer

Gram stain

Answer

Split skin smear

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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