Fungal Skin Infections Practice Questions

Q: The underlying cause of chronic paronychia is:

Contact dermatitis/Inflammatory. ***Correct: Contact dermatitis/Inflammatory*** - **Chronic paronychia** is fundamentally an **inflammatory/eczematous condition** of the proximal nail fold, not a primary infection - The underlying cause is **repeated exposure to irritants** (water, detergents, chemicals) or **allergens** leading to chronic inflammation - This inflammation causes **separation of the cuticle from the nail plate**, disrupting the protective barrier - **Loss of the cuticle seal** allows moisture accumulation and creates an environment for secondary colonization - The inflammatory process itself is the primary pathology that must be addressed for successful treatment *Incorrect: Bacterial (secondary colonization)* - Bacteria such as *Staphylococcus aureus* or *Pseudomonas aeruginosa* can secondarily colonize the inflamed nail fold - However, they are **not the underlying cause** but rather opportunistic colonizers after barrier disruption - Treating with antibiotics alone often fails because it doesn't address the primary inflammatory process - Bacterial colonization is much less common than candidal colonization in chronic paronychia *Incorrect: Fungal (secondary colonization)* - *Candida* species (especially *C. albicans*) are the **most common secondary colonizers** in chronic paronychia - Candida thrives in the moist environment created by cuticle disruption - While frequently present, Candida is a **consequence rather than the cause** of chronic paronychia - Antifungal therapy alone often provides temporary relief but recurrence is common without addressing the underlying inflammation *Incorrect: Viral* - Viral infections such as **herpetic whitlow** (HSV) cause **acute** painful vesicular lesions of the distal finger - Viral infections are not associated with chronic paronychia - Clinical presentation of viral nail infections differs significantly with vesicles and a self-limited course

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: Which organism does not affect hair?

Epidermophyton floccosum. ***Epidermophyton floccosum*** - This fungus primarily affects the **skin and nails**, causing conditions like **tinea cruris** (jock itch) and **tinea pedis** (athlete's foot). - Unlike *Trichophyton* and *Microsporum*, *Epidermophyton floccosum* does not have the enzymatic machinery to invade or colonize hair shafts. *Trichophyton rubrum* - This organism is a common cause of **dermatophytosis**, and it frequently infects hair, particularly in conditions like **tinea capitis** (scalp ringworm) and **tinea barbae**. - It can invade the hair shaft both **endothrix** (inside the hair) and **ectothrix** (outside the hair) depending on the species and type of infection. *Microsporum* - *Microsporum* species are well-known for causing infections of the hair and are a major cause of **tinea capitis**, especially in children. - The infection typically presents as an **ectothrix** pattern, where fungal spores are found on the outside of the hair shaft. *All of the options* - This option is incorrect because both *Trichophyton rubrum* and *Microsporum* species are known to infect hair. - Only *Epidermophyton floccosum* does not typically affect hair.

Q: Wood's Lamp is used in the diagnosis of:

Pityriasis versicolor. ***Pityriasis versicolor*** - A Wood's lamp is used to diagnose **Pityriasis versicolor** as the affected areas fluoresce a characteristic **golden yellow** (sometimes yellow-green) color due to the presence of porphyrins produced by the Malassezia fungus. - This diagnostic tool helps in visualizing subtle lesions and confirming the diagnosis of this superficial fungal infection. *Tinea pedis* - **Tinea pedis**, or athlete's foot, is typically diagnosed clinically based on symptoms like **itching, scaling, and redness**, or through **potassium hydroxide (KOH) microscopy** of skin scrapings to visualize hyphae. - A Wood's lamp is generally **not useful** for Tinea pedis, as the causative dermatophytes usually do not fluoresce. *Sporotrichosis* - **Sporotrichosis** is a subcutaneous fungal infection usually diagnosed by **fungal culture** from lesional tissue or aspiration, and sometimes by **histopathology**. - A Wood's lamp is **not used** in the diagnosis of sporotrichosis as the Sporothrix schenckii fungus does not exhibit fluorescence under UV light. *All of the options* - This option is incorrect because a Wood's lamp is only reliably used for **Pityriasis versicolor** among the given choices, due to the characteristic fluorescence of the causative organism. - It does not aid in the diagnosis of **Tinea pedis** or **Sporotrichosis**.

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.

Question 1

The underlying cause of chronic paronychia is:

Accepted Answer

Contact dermatitis/Inflammatory

Answer

Bacterial (secondary colonization)

Answer

Fungal (secondary colonization)

Answer

Viral

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

Which organism does not affect hair?

Accepted Answer

Epidermophyton floccosum

Answer

Trichophyton rubrum

Answer

Microsporum

Answer

All of the options

Question 8

Wood's Lamp is used in the diagnosis of:

Accepted Answer

Pityriasis versicolor

Answer

Tinea pedis

Answer

Sporotrichosis

Answer

All of the options

Question 9

Drug not given in treatment of tinea versicolor?

Accepted Answer

Griseofulvin

Answer

Ketoconazole

Answer

Selenium sulfide

Answer

Miconazole

Question 10

Tinea Manuum affects

Accepted Answer

Hands

Answer

Nails

Answer

Face

Answer

Foot

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?