Fungal Skin Infections Practice Questions

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.

Q: Dermatophytes primarily involve _______:

Stratum corneum. ***Stratum corneum*** - Dermatophytes are **keratinophilic fungi** that thrive on **keratin**, the primary protein found in the stratum corneum, hair, and nails. - They cause superficial infections by colonizing and breaking down the keratinized layers, leading to conditions like **tinea corporis** or **athlete's foot**. *Stratum basale* - This layer contains **actively dividing keratinocytes** and melanocytes and is the deepest epidermal layer. - Dermatophytes do not typically reach this layer, as the host immune response and the process of **epidermal turnover** would usually prevent deeper invasion. *Stratum granulosum* - This layer is characterized by cells containing **keratohyalin granules** and marks the transition from metabolically active cells to terminally differentiated cells. - While located above the stratum basale, it is generally spared from primary dermatophyte invasion, which targets the more superficial, fully keratinized layers. *Stratum spinosum* - Layers are several cells thick and characterized by **desmosomes**, which provide strength and flexibility to the epidermis. - It is located deeper than the stratum corneum, and dermatophytes typically do not penetrate this layer, as their growth is confined to the **non-living keratinized tissue** above.

Q: Ringworm fungi live in

Stratum Corneum. ***Stratum Corneum*** - **Dermatophytes**, the fungi causing ringworm, are keratinophilic and thrive in the **superficial keratinized layers** of the skin. - The **stratum corneum** is the outermost layer of the epidermis, composed of dead cells rich in keratin, providing an ideal environment for these fungi. *Basal Cell layer* - The **basal cell layer** (stratum basale) is the deepest layer of the epidermis, responsible for cell proliferation. - Dermatophytes usually do not penetrate beyond the **stratum granulosum** and are rarely found in the basal layer. *Prickle Cell layer* - The **prickle cell layer** (stratum spinosum) is located just above the basal layer and contains actively metabolizing keratinocytes. - While dermatophytes can cause inflammatory reactions in these deeper epidermal layers, their primary habitat and growth occur superficially in the **stratum corneum**. *Dermis* - The **dermis** is the layer of skin beneath the epidermis, containing connective tissue, blood vessels, nerves, and hair follicles. - Dermatophytes generally do not invade the dermis, as they are specifically adapted to colonize **keratinized structures** and the immune system typically contains them within the epidermis.

Q: 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?

KOH mount. ***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.

Q: A 7 year old boy with boggy swelling of the scalp with multiple discharging sinuses with cervical lymphadenopathy with easily pluckable hair. What would be done for diagnosis?

KOH mount. ***KOH mount*** - A **KOH mount** (potassium hydroxide wet mount) is the most appropriate **initial rapid diagnostic test** for suspected **tinea capitis** with **kerion formation**, allowing immediate visualization of fungal elements (hyphae and spores). - The clinical presentation of boggy scalp swelling, discharging sinuses, cervical lymphadenopathy, and easily pluckable hair is classic for **kerion**, a severe inflammatory form of tinea capitis caused by dermatophytes (commonly *Trichophyton* or *Microsporum* species). - KOH mount is **quick, inexpensive, and readily available**, making it ideal for immediate diagnosis in clinical practice, though fungal culture may be performed subsequently for species identification. *Pus for culture (bacterial)* - While bacterial culture might be performed to rule out **secondary bacterial infection**, it does not diagnose the underlying **fungal etiology** of kerion. - The primary pathogen in kerion is a dermatophyte fungus, not bacteria, though secondary bacterial infection can occur. *Biopsy* - A **biopsy** is usually reserved for cases that are atypical, treatment-resistant, or when there is diagnostic uncertainty with other conditions (e.g., dissecting cellulitis, bacterial abscess). - It is an **invasive procedure** and not the first-line diagnostic approach for a clinically obvious case of kerion. *None of the options* - Given the classic clinical presentation of kerion, a definitive diagnostic method (KOH mount) is required to confirm the fungal infection and guide appropriate systemic antifungal treatment. - Therefore, choosing "None of the options" would be incorrect.

Q: Tinea incognito is seen with:

Steroid treatment. ***Steroid treatment*** - **Tinea incognito** refers to a dermatophyte infection whose appearance has been altered by the application of **topical corticosteroids**. - Steroids suppress the immune response, allowing the fungal infection to spread and making its characteristic features less apparent or even masked. *5% permethrin* - **Permethrin** is an insecticide commonly used to treat parasitic infestations such as **scabies** and **lice**. - It has no antifungal properties and would not lead to tinea incognito; rather, it would be ineffective against a fungal infection. *Antibiotics* - **Antibiotics** are medications used to treat **bacterial infections**. - They are ineffective against fungal infections and would not cause tinea incognito. *Antifungal cream* - **Antifungal creams** are used to treat fungal infections, including tinea. - While inappropriate use or misdiagnosis could delay proper treatment, antifungal creams themselves would not cause tinea incognito, which is specifically a result of steroid use.

Q: Drug not given in treatment of tinea versicolor?

Griseofulvin. ***Griseofulvin*** - **Griseofulvin** works by binding to **keratin** and interfering with fungal cell division, making it effective for dermatophyte infections of the **skin, hair, and nails**. - It is not effective against **Malassezia species**, which cause tinea versicolor, rendering it unsuitable for this condition. *Ketoconazole* - **Ketoconazole** is an azole antifungal that inhibits **ergosterol synthesis**, a crucial component of fungal cell membranes. - It is effective against **Malassezia species** and is a common treatment for tinea versicolor, available topically and orally. *Selenium sulfide* - **Selenium sulfide** is an antifungal and keratolytic agent that slows the growth of **Malassezia species**. - It is commonly used as a **topical shampoo or lotion** for tinea versicolor due to its efficacy in clearing the fungal overgrowth. *Miconazole* - **Miconazole** is another azole antifungal that disrupts **fungal cell membrane integrity** by inhibiting ergosterol synthesis. - It is effective against **Malassezia species** and is widely used as a **topical cream or spray** for tinea versicolor.

Q: Tinea Manuum affects

Hands. ***Hands*** - **Tinea manuum** is a dermatophyte infection specifically affecting the skin of the **hands**. - It often presents as a **unilateral** scaling, red, or macerated rash, sometimes mistaken for eczema or contact dermatitis. *Nails* - Fungal infections of the nails are known as **onychomycosis** or **tinea unguium**, not tinea manuum. - While sometimes associated with tinea manuum, it is a distinctly separate condition affecting the **nail plate**. *Face* - Fungal infections on the face are referred to as **tinea faciei**. - This condition presents with well-demarcated, erythematous, and scaly patches on the face. *Foot* - Fungal infections on the foot are most commonly known as **tinea pedis**, also called **athlete's foot**. - Tinea pedis typically affects the soles, interdigital spaces, or sides of the feet.

Q: In Wood's lamp examination, Tinea versicolor looks like

Yellow fluorescence. ***Yellow fluorescence*** - **Tinea versicolor** (Pityriasis versicolor) caused by *Malassezia* species characteristically shows **golden-yellow to yellow-green fluorescence** under Wood's lamp examination. - This fluorescence is due to **pityriacitrin**, a fluorescent substance produced by the fungus. - This finding helps confirm the diagnosis and distinguish it from other skin conditions. *Non-fluorescent (appears dark)* - This is incorrect for Tinea versicolor, which does show fluorescence. - Conditions that appear non-fluorescent include vitiligo (appears bright white due to lack of melanin but doesn't fluoresce). *Blue-green fluorescence* - This is characteristic of **Pseudomonas aeruginosa** infections due to pyocyanin production. - Seen in wound infections, ecthyma gangrenosum, and folliculitis. - Not associated with Tinea versicolor. *Coral-red fluorescence* - This is pathognomonic for **Erythrasma**, caused by *Corynebacterium minutissimum*. - The coral-red color is due to coproporphyrin III production by the bacteria. - This bright fluorescence easily distinguishes Erythrasma from fungal infections.

Q: A patient presents with tinea corporis showing minimal response to terbinafine. What is the most likely cause?

Microsporum canis. ***Microsporum canis*** - *Microsporum canis* is a **zoophilic dermatophyte** (acquired from animals, especially cats and dogs) that shows **reduced susceptibility to terbinafine** compared to *Trichophyton* species. - The *Microsporum* genus has inherently **lower response rates to terbinafine** due to differences in fungal cell wall composition and drug target affinity. - Treatment of *M. canis* infections typically requires **griseofulvin or azole antifungals** (itraconazole, fluconazole) rather than terbinafine for optimal outcomes. - Minimal response to terbinafine in tinea corporis should prompt consideration of *Microsporum* infection. *Trichophyton rubrum* - *Trichophyton rubrum* is the **most common cause of tinea corporis** and shows **excellent response to terbinafine**. - This is typically the most terbinafine-susceptible dermatophyte, making treatment failure with adequate therapy highly unlikely. - Minimal response would only occur with poor compliance, incorrect diagnosis, or very rare resistance. *Trichophyton mentagrophytes* - *Trichophyton mentagrophytes* is a common cause of tinea corporis with **good susceptibility to terbinafine**. - This species typically responds well to standard terbinafine therapy. - Treatment failure would be uncommon with proper dosing and compliance. *Trichophyton tonsurans* - *Trichophyton tonsurans* primarily causes **tinea capitis** but can also cause tinea corporis. - Shows **good response to terbinafine** and would not typically present with treatment resistance. - Not the most likely explanation for terbinafine failure in tinea corporis.

Question 1

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

Question 2

Dermatophytes primarily involve _______:

Accepted Answer

Stratum corneum

Answer

Stratum basale

Answer

Stratum granulosum

Answer

Stratum spinosum

Question 3

Ringworm fungi live in

Accepted Answer

Stratum Corneum

Answer

Basal Cell layer

Answer

Prickle Cell layer

Answer

Dermis

Question 4

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?

Accepted Answer

KOH mount

Answer

Tzanck smear

Answer

Woods lamp

Answer

Biopsy

Question 5

A 7 year old boy with boggy swelling of the scalp with multiple discharging sinuses with cervical lymphadenopathy with easily pluckable hair. What would be done for diagnosis?

Accepted Answer

KOH mount

Answer

Pus for culture

Answer

Biopsy

Answer

None of the options

Question 6

Tinea incognito is seen with:

Accepted Answer

Steroid treatment

Answer

5% permethrin

Answer

Antibiotics

Answer

Antifungal cream

Question 7

Drug not given in treatment of tinea versicolor?

Accepted Answer

Griseofulvin

Answer

Ketoconazole

Answer

Selenium sulfide

Answer

Miconazole

Question 8

Tinea Manuum affects

Accepted Answer

Hands

Answer

Nails

Answer

Face

Answer

Foot

Question 9

In Wood's lamp examination, Tinea versicolor looks like

Accepted Answer

Yellow fluorescence

Answer

Non-fluorescent (appears dark)

Answer

Blue-green fluorescence

Answer

Coral-red fluorescence

Question 10

A patient presents with tinea corporis showing minimal response to terbinafine. What is the most likely cause?

Accepted Answer

Microsporum canis

Answer

Trichophyton mentagrophytes

Answer

Trichophyton tonsurans

Answer

Trichophyton rubrum

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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