Fungal Skin Infections Practice Questions

Q: A 24 year old man had multiple, small hypopigmented macules on the upper chest and back for the last three months. The macules were circular, arranged around follicles and many had coalesced to form large sheets. The surface of the macules showed fine scaling. He had similar lesions one year ago which subsided with treatment. The most appropriate investigation to confirm the diagnosis is -

Potassium hydroxide preparation of scales. ***Potassium hydroxide preparation of scales*** - The description of **hypopigmented macules** with **fine scaling** on the upper chest and back, which coalesced and recurred, is highly suggestive of **Pityriasis versicolor** (also known as Tinea versicolor). - A **potassium hydroxide (KOH) preparation** of the scales directly visualizes the fungal elements (**hyphae and spores**, often described as "spaghetti and meatballs" appearance), confirming the diagnosis. *Slit skin smear from discrete macules* - A **slit skin smear** is primarily used for diagnosing mycobacterial infections, particularly **leprosy**, to detect acid-fast bacilli. - This procedure is not appropriate for diagnosing superficial fungal infections like Pityriasis versicolor. *Skin biopsy of coalesced macules* - While a **skin biopsy** can show fungal elements in the stratum corneum, it is an invasive and generally unnecessary procedure for diagnosing Pityriasis versicolor. - **KOH preparation** is a faster, simpler, and less invasive method that provides a definitive diagnosis. *Tzanck test* - The **Tzanck test** is used to identify multinucleated giant cells characteristic of viral infections, such as **herpes simplex virus** or **varicella-zoster virus**. - It involves scraping the base of a vesicle or bulla, which is not consistent with the described presentation of scaling macules.

Q: Which of the following is the location beyond which fungus does not penetrate in tinea capitis ?

Adamson's fringe. ***Adamson's fringe*** - Adamson's fringe is the **critical anatomical boundary** located at the opening of the sebaceous gland duct into the hair follicle. - It represents the zone where **hair keratinization is complete** and marks the transition between the keratinized (dead) upper portion and the living, pre-keratinized hair matrix below. - In tinea capitis, dermatophyte fungi **cannot penetrate beyond Adamson's fringe** because they are keratinophilic organisms that can only invade fully keratinized tissue [1]—they cannot survive in the living hair bulb below this level. - This is the **deepest point of fungal penetration** in the hair follicle. *Isthmus* - The isthmus is the mid-portion of the hair follicle located **between the insertion of the arrector pili muscle and the opening of the sebaceous gland**. - It is **above/superficial to Adamson's fringe**, meaning fungi can and do penetrate through this region as they invade downward toward Adamson's fringe. - Therefore, the isthmus is **not the limiting boundary** of fungal penetration. *Infundibulum* - The infundibulum is the **uppermost segment** of the hair follicle, extending from the skin surface down to the sebaceous gland opening. - This is the **most superficial region** where fungal infection typically begins in tinea capitis. - Fungi are readily present in the infundibulum but penetrate **deeper than this level**, making it not the limiting boundary. *Stem* - "Stem" refers to the **hair shaft itself** (the visible, keratinized hair fiber) rather than a specific anatomical boundary within the follicle. - While fungi do invade the hair stem/shaft, this term does not define the **anatomical limit of penetration within the follicle architecture**—that limit is specifically Adamson's fringe. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 638-639.

Q: 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?

KOH mount. ***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.

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**.

Question 1

A 24 year old man had multiple, small hypopigmented macules on the upper chest and back for the last three months. The macules were circular, arranged around follicles and many had coalesced to form large sheets. The surface of the macules showed fine scaling. He had similar lesions one year ago which subsided with treatment. The most appropriate investigation to confirm the diagnosis is -

Accepted Answer

Potassium hydroxide preparation of scales

Answer

Slit skin smear from discrete macules

Answer

Skin biopsy of coalesced macules

Answer

Tzanck test

Question 2

Which of the following is the location beyond which fungus does not penetrate in tinea capitis ?

Accepted Answer

Adamson's fringe

Answer

Isthmus

Answer

Infundibulum

Answer

Stem

Question 3

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?

Accepted Answer

KOH mount

Answer

Bacterial culture

Answer

Biopsy and giemsa staining

Answer

Patch test, gram staining and Tzank smear

Question 4

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 5

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

Accepted Answer

Steroids

Answer

Antibiotics

Answer

Antivirals

Answer

Antifungals

Question 6

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 7

Best diagnostic test for fungal skin infection –

Accepted Answer

KOH test

Answer

Diascopy

Answer

Patch test

Answer

Wood's lamp

Question 8

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 9

Majocchi granuloma is due to:

Accepted Answer

Trichophyton

Answer

Microsporum

Answer

Microsporum gypseum

Answer

Epidermophyton

Question 10

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

Accepted Answer

Griseofulvin

Answer

Selenium sulfide

Answer

Clotrimazole

Answer

Ketoconazole

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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