Fungal Skin Infections Practice Questions

Q: What is the drug of choice for treating onychomycosis?

Terbinafine. ***Terbinafine*** - **Terbinafine** is the preferred first-line oral antifungal agent for treating **onychomycosis** due to its high efficacy and favorable safety profile. - It accumulates in the nail plate, providing sustained therapeutic levels that result in high cure rates. *Fluconazole* - While effective against some fungal infections, **fluconazole** is typically a second-line choice for onychomycosis, often reserved for patients who cannot tolerate or prefer not to use terbinafine. - It has a broader spectrum but generally shows lower efficacy for dermatophyte-induced onychomycosis compared to terbinafine. *Nystatin* - **Nystatin** is primarily effective against **Candida** species and is rarely effective against the **dermatophytes** that commonly cause onychomycosis. - It is typically used for topical treatment of mucocutaneous candidiasis and is not suitable for systemic or nail plate penetration. *Itraconazole* - **Itraconazole** is an effective oral antifungal for onychomycosis, often used in a pulse-dosing regimen, but it can have more significant drug interactions and a less favorable safety profile than terbinafine. - It is considered an alternative or second-line agent, especially in cases where terbinafine is not tolerated or effective.

Q: A patient presents with a red, itchy, annular rash with central clearing on the upper arm. Identify the most likely causative organism.

Trichophyton rubrum. ***Trichophyton rubrum*** - This dermatophyte is a **common cause** of fungal skin infections, such as tinea corporis (ringworm), which presents as a red, itchy rash. - It can infect the **skin, hair, and nails**, leading to characteristic skin lesions. *Malassezia furfur* - This yeast is responsible for **tinea versicolor**, characterized by hypopigmented or hyperpigmented patches, not typically a classic red, itchy rash on the upper arm. - It primarily affects areas rich in **sebaceous glands** like the chest and back. *Candida albicans* - While it can cause skin infections (e.g., **candidiasis**), it typically presents as bright red, often weeping patches with satellite lesions in intertriginous areas (skin folds), rather than a general red, itchy rash on the upper arm. - Predisposing factors include **diabetes, obesity, and immunosuppression**. *Aspergillus niger* - This fungus is more commonly associated with **invasive pulmonary aspergillosis** in immunocompromised individuals or external otitis, rather than superficial skin infections. - It primarily affects the **respiratory tract** and, in rare cases, can cause disseminated disease.

Q: A 40-year-old male patient presents with multiple erythematous annular lesions with peripheral scales arranged predominantly on the trunk. What is the most appropriate treatment option?

Topical antifungal. ***Topical antifungal*** - The description of **erythematous annular lesions** with **peripheral scales** predominantly on the **trunk** is highly suggestive of **tinea corporis** (ringworm), a superficial fungal infection. - **Topical antifungals** (clotrimazole, miconazole, terbinafine) are first-line treatment for localized tinea corporis. - **Clinical Note**: While this patient has **multiple lesions**, which would typically favor **systemic antifungals** (oral terbinafine or itraconazole) for better coverage and compliance, topical antifungal is the most appropriate option among the choices provided. - Treatment duration: 2-4 weeks, extending 1-2 weeks beyond clinical clearance. *Topical steroids* - While steroids can reduce inflammation and erythema, they **do not treat the underlying fungal infection**. - Using topical steroids alone on a fungal infection can lead to **tinea incognito**, where the infection spreads and changes its clinical appearance, making diagnosis more difficult. - Steroids may be used **in combination** with antifungals for symptomatic relief in highly inflamed cases, but never as monotherapy. *Systemic steroids* - **Completely inappropriate** for superficial fungal infections due to immunosuppressive effects. - Would worsen the fungal infection by suppressing the immune response. - Reserved for severe inflammatory dermatoses (pemphigus, severe eczema) or autoimmune conditions, not infections. *Systemic Azathioprine* - **Azathioprine** is an **immunosuppressant** used for autoimmune conditions (lupus, pemphigus) or organ transplantation. - Completely unsuitable and potentially harmful for fungal infections, as it would suppress cell-mediated immunity and worsen the infection. - No role in infectious dermatoses.

Q: What is the primary cause of jock itch?

Trichophyton rubrum. ***Trichophyton rubrum*** - *Trichophyton rubrum* is the most common **dermatophyte** species responsible for **tinea cruris**, commonly known as jock itch. - This fungus thrives in warm, moist environments, making the groin area an ideal site for infection. *Candida albicans* - While *Candida albicans* can cause skin infections, particularly in warm and moist areas (e.g., **candidal intertrigo**), it is typically not the primary cause of classical jock itch (*tinea cruris*). - Candidal infections often present with distinct satellite lesions and a more intensely red, eroded appearance compared to dermatophyte infections. *Trichophyton tonsurans* - *Trichophyton tonsurans* is primarily known for causing **tinea capitis** (ringworm of the scalp), especially in children. - It is not a common cause of jock itch. *Malassezia furfur* - *Malassezia furfur* is a yeast species responsible for **tinea versicolor**, a superficial fungal infection characterized by discolored patches on the skin. - It is not a typical cause of jock itch, which is usually caused by dermatophytes like *Trichophyton rubrum*.

Q: Which of the following is not a clinical feature of candidal intertrigo?

Central scaling. ***Central scaling*** - **Central scaling** is **NOT a typical feature** of candidal intertrigo, making this the correct answer. - Candidal intertrigo presents with **moist, erythematous patches** in skin folds, not with prominent central scaling. - Central scaling is more characteristic of **dermatophyte infections** like **tinea corporis** (ringworm), which shows an active, scaly border with central clearing. *Satellite lesions* - **Satellite lesions** are a **pathognomonic feature** of candidal intertrigo. - These small papules and pustules surrounding the main erythematous plaque result from yeast spread beyond the primary lesion borders. - Their presence helps distinguish candidal from bacterial intertrigo. *Maceration* - **Maceration** (softening and whitening of skin due to moisture) is a **classic feature** of candidal intertrigo. - Occurs in intertriginous areas (groin, axillae, under breasts) where skin-on-skin contact traps moisture. - The moist environment favors Candida growth and contributes to the characteristic appearance. *Pustular lesions* - **Pustules** are commonly seen in candidal intertrigo, often as satellite lesions or within the main plaque. - These pustules indicate active inflammatory response to the fungal infection. - Their presence, along with erythema and satellite lesions, supports the diagnosis of candidal intertrigo.

Q: Most common pattern of onychomycosis is?

Distal and lateral subungual. ***Distal and lateral subungual*** - This pattern, often caused by dermatophytes like *Trichophyton rubrum*, accounts for the **majority of onychomycosis cases** (80-90%). - It begins at the **distal nail plate** or **lateral nail folds** and spreads proximally under the nail. *Proximal subungual* - This pattern is less common and often indicative of **immunosuppression**, such as in HIV/AIDS patients. - The infection starts at the **proximal nail fold** and spreads distally. *White superficial* - This type of onychomycosis is characterized by **white, powdery patches** on the surface of the nail plate. - It is caused by superficial fungal invasion and can be **scraped off easily**. *Total dystrophic* - This pattern represents the most **advanced and severe form** of onychomycosis, often developing from other types. - The entire nail unit is affected, leading to gross **thickening, discoloration, and crumbling** of the nail.

Q: Onychomycosis is most commonly caused by which of the following fungi?

1) Trichophyton rubrum. **1) Trichophyton rubrum** - **Trichophyton rubrum** is the most common dermatophyte causing **onychomycosis**, responsible for up to 80-90% of cases. - It typically causes **distal and lateral subungual onychomycosis**, leading to nail thickening and discoloration. *2) Trichophyton mentagrophytes* - **Trichophyton mentagrophytes** is another common dermatophyte but is less frequently implicated in onychomycosis compared to *T. rubrum*. - It is more commonly associated with **tinea pedis (athlete's foot)** and **tinea corporis (ringworm)**. *3) Epidermophyton floccosum* - **Epidermophyton floccosum** can cause various dermatophytoses, including **tinea cruris (jock itch)** and **tinea pedis**. - While it can occasionally affect nails, it is not a primary or common cause of onychomycosis. *4) Candida* - **Candida** species, particularly *Candida albicans*, can cause onychomycosis, especially in individuals with **chronic mucocutaneous candidiasis** or those whose hands are frequently wet. - However, **Candida** is a yeast and is less common as a cause of onychomycosis than dermatophytes like *Trichophyton rubrum*, which are molds.

Q: Identify the condition causing this infection on the upper arm

Tinea corporis (body ringworm). ***Tinea corporis (body ringworm)*** - This lesion, depicted on the upper arm, is characteristic of **tinea corporis** due to its **annular, erythematous, and scaly border with central clearing**. - The term "corporis" refers to the **body surface**, excluding the scalp, hands, feet, groin, and nails. *Tinea capitis (scalp ringworm)* - Tinea capitis specifically affects the **scalp** and can present with scaling, hair loss, and inflammation. - The image clearly shows a lesion on the **upper arm**, not the scalp. *Tinea cruris (jock itch)* - Tinea cruris is a fungal infection found in the **groin area**, often extending to the inner thighs and buttocks. - The location of the lesion in the image, on the **upper arm**, rules out tinea cruris. *Tinea manus (hand ringworm)* - Tinea manus affects the **hands**, typically causing dryness, scaling, and sometimes blister formation on the palms or between the fingers. - The lesion in the image is located on the **upper arm**, not the hand.

Q: Skin scraping and KOH mounting is primarily used to diagnose which of the following conditions?

Dermatophyte infection. ***Dermatophyte infection*** - Skin scraping followed by **KOH mounting** is the **primary and gold standard** diagnostic method for dermatophyte infections - **Potassium hydroxide (KOH)** dissolves keratin, making **fungal hyphae and arthroconidia** clearly visible under microscopy - This is the **most common indication** for KOH preparation in dermatology practice - Demonstrates **septate hyphae** characteristic of dermatophytes *Candidiasis* - KOH mounting can also identify *Candida* species by revealing **pseudohyphae and budding yeast cells** - While KOH can diagnose candidiasis, dermatophyte infections remain the **primary and most frequent indication** for this test in skin lesions - Candida more commonly affects mucosal surfaces where other diagnostic methods may be preferred *Bacterial infection* - Bacterial infections are diagnosed using **Gram stain, culture, and sensitivity** testing - KOH mounting is specifically for **fungal elements** and does not visualize bacteria effectively - Bacterial skin infections require different diagnostic approaches *Herpes Simplex Virus (HSV)* - HSV infections are diagnosed using **Tzanck smear** (showing multinucleated giant cells), **viral culture, or PCR** - KOH mounting is exclusively for fungal identification and **cannot detect viruses** - Viral cytopathic effects are not visible with KOH preparation

Q: Which of the following drugs is effective in the treatment of pityriasis versicolor?

Ketoconazole. ***Ketoconazole*** - **Ketoconazole** is an **azoles antifungal agent** effective against the *Malassezia* species, the causative agent of **pityriasis versicolor**. - It works by inhibiting the synthesis of **ergosterol**, a crucial component of the fungal cell membrane, leading to its disruption and fungal cell death. *Metronidazole* - **Metronidazole** is an **antibiotic** and **amoebicide** primarily used to treat bacterial and parasitic infections. - It has **no antifungal activity** and is thus ineffective against *Malassezia* or other fungal infections. *Griseofulvin* - **Griseofulvin** is an **oral antifungal drug** primarily used for **dermatophyte infections** of the skin, hair, and nails (e.g., tinea capitis, onychomycosis). - It is **ineffective against yeasts and molds**, including *Malassezia*, making it unsuitable for pityriasis versicolor. *Chloroquine* - **Chloroquine** is an **antimalarial drug** also used in the treatment of some autoimmune conditions like lupus erythematosus. - It possesses **no antifungal properties** and is not used to treat fungal infections of any kind.

Question 1

What is the drug of choice for treating onychomycosis?

Accepted Answer

Terbinafine

Answer

Fluconazole

Answer

Nystatin

Answer

Itraconazole

Question 2

A patient presents with a red, itchy, annular rash with central clearing on the upper arm. Identify the most likely causative organism.

Accepted Answer

Trichophyton rubrum

Answer

Candida albicans

Answer

Malassezia furfur

Answer

Aspergillus niger

Question 3

A 40-year-old male patient presents with multiple erythematous annular lesions with peripheral scales arranged predominantly on the trunk. What is the most appropriate treatment option?

Accepted Answer

Topical antifungal

Answer

Systemic steroids

Answer

Systemic Azathioprine

Answer

Topical steroids

Question 4

What is the primary cause of jock itch?

Accepted Answer

Trichophyton rubrum

Answer

Candida albicans

Answer

Trichophyton tonsurans

Answer

Malassezia furfur

Question 5

Which of the following is not a clinical feature of candidal intertrigo?

Accepted Answer

Central scaling

Answer

Satellite lesions

Answer

Maceration

Answer

Pustular lesions

Question 6

Most common pattern of onychomycosis is?

Accepted Answer

Distal and lateral subungual

Answer

Proximal subungual

Answer

White superficial

Answer

Total dystrophic

Question 7

Onychomycosis is most commonly caused by which of the following fungi?

Accepted Answer

1) Trichophyton rubrum

Answer

2) Trichophyton mentagrophytes

Answer

3) Epidermophyton floccosum

Answer

4) Candida

Question 8

Identify the condition causing this infection on the upper arm

Accepted Answer

Tinea corporis (body ringworm)

Answer

Tinea capitis (scalp ringworm)

Answer

Tinea cruris (jock itch)

Answer

Tinea manus (hand ringworm)

Question 9

Skin scraping and KOH mounting is primarily used to diagnose which of the following conditions?

Accepted Answer

Dermatophyte infection

Answer

Bacterial infection

Answer

Candidiasis

Answer

Herpes Simplex Virus (HSV)

Question 10

Which of the following drugs is effective in the treatment of pityriasis versicolor?

Accepted Answer

Ketoconazole

Answer

Metronidazole

Answer

Griseofulvin

Answer

Chloroquine

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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