Fungal Skin Infections — MCQs

Fungal Skin Infections Indian Medical PG Practice Questions and MCQs

Question 81: All of the following is/are true regarding candidiasis, except:

A. Commonly involve mucosa and skin.
B. Involves nails. (Correct Answer)
C. Caused by yeast-like fungus.
D. Diabetes is an important risk factor.

Explanation: **Explanation:** The correct answer is **B (Involves nails)**. While *Candida* can affect the periungual tissue (causing chronic paronychia), it **rarely involves the nail plate itself** (onychomycosis). True fungal nail plate infections are predominantly caused by dermatophytes (e.g., *Trichophyton rubrum*). In candidal paronychia, the primary pathology is inflammation of the nail fold, which may secondarily lead to nail dystrophy, but the fungus does not typically invade the hard keratin of the nail plate. **Analysis of other options:** * **Option A:** *Candida* species are commensals that frequently cause opportunistic infections of the **mucosa** (oral thrush, vulvovaginitis) and **moist skin** (intertrigo). * **Option C:** *Candida albicans* is a **yeast-like fungus**. It is dimorphic, existing as budding yeast cells (blastospores) and pseudohyphae in tissue. * **Option D:** **Diabetes mellitus** is a classic risk factor. High glucose levels promote fungal growth and impair neutrophil function, making diabetics prone to recurrent candidiasis. **NEET-PG High-Yield Pearls:** * **Satellite Lesions:** The presence of "satellite pustules" or papules beyond the main border of erythema is a pathognomonic clinical sign of cutaneous candidiasis. * **KOH Mount:** Shows characteristic budding yeast and **pseudohyphae**. * **Chronic Mucocutaneous Candidiasis (CMC):** Associated with T-cell immunodeficiency and endocrine disorders (e.g., hypoparathyroidism). * **Treatment:** Topical azoles or nystatin for skin; oral fluconazole for systemic or resistant mucosal cases.

Question 82: Dermatophytes primarily infect which structures of the body?

A. Subcutaneous tissue
B. Systemic organs
C. Nails, hair, and skin (Correct Answer)
D. Superficial skin and deep tissue

Explanation: **Explanation:** **Dermatophytes** are a group of closely related fungi (genera: *Trichophyton*, *Microsporum*, and *Epidermophyton*) that are **keratinophilic**, meaning they have a unique affinity for keratin. They produce the enzyme **keratinase**, which allows them to digest and colonize keratinized tissues. Since keratin is found exclusively in the **stratum corneum of the skin, hair, and nails**, these are the primary sites of infection. **Analysis of Options:** * **Option C (Correct):** Dermatophytes are restricted to the non-living cornified layers of the skin and its appendages (hair and nails) because they cannot survive at body temperature (37°C) or in the presence of serum. * **Option A & D (Incorrect):** Dermatophytes do not typically invade the **subcutaneous or deep tissues**. Such infections are usually caused by deep fungi (e.g., Mycetoma, Sporotrichosis) or opportunistic molds. * **Option B (Incorrect):** **Systemic organs** are involved in systemic mycoses (e.g., Histoplasmosis) or candidiasis, but never in dermatophytosis, as these fungi lack the ability to invade living tissue or withstand internal body temperatures. **NEET-PG High-Yield Pearls:** * **The "Rule of Three":** Remember the three genera: *Trichophyton* (infects skin, hair, and nails), *Microsporum* (skin and hair), and *Epidermophyton* (skin and nails—**never hair**). * **Tinea Incognito:** This occurs when a dermatophyte infection is modified by the application of topical steroids, leading to a loss of the classic annular (ring-like) appearance. * **Diagnosis:** The gold standard screening is **KOH mount**, which shows branching septate hyphae. Culture is done on **Sabouraud’s Dextrose Agar (SDA)**.

Question 83: Which layer of the skin do dermatophytes primarily involve?

A. Stratum corneum (Correct Answer)
B. Stratum lucidum
C. Stratum malpighi
D. Stratum basale

Explanation: **Explanation:** Dermatophytes (genera *Trichophyton*, *Microsporum*, and *Epidermophyton*) are unique fungi that possess **keratinolytic enzymes** (keratinases). These enzymes allow them to digest and metabolize keratin as their primary nutrient source. Consequently, these infections are strictly limited to the **Stratum corneum** (the outermost, keratinized layer of the epidermis) and other keratin-containing structures like hair and nails. They do not typically invade deeper, viable tissues in immunocompetent hosts because they are inhibited by serum factors and the body's inflammatory response. **Analysis of Incorrect Options:** * **B. Stratum lucidum:** This is a thin, clear layer found only in thick skin (palms and soles). While dermatophytes can inhabit this area, their primary niche is the broader keratinized surface of the corneum. * **C. Stratum malpighi:** This refers to the combined layer of the Stratum spinosum and Stratum basale. These are living, nucleated cells with minimal mature keratin; therefore, dermatophytes do not colonize this layer. * **D. Stratum basale:** This is the deepest, germinative layer of the epidermis. Dermatophytes do not reach this level as it lacks the dead, cornified keratin required for their survival. **Clinical Pearls for NEET-PG:** * **Wood’s Lamp:** Used for diagnosis; *Microsporum* species typically show a brilliant green fluorescence. * **KOH Mount:** The gold standard for rapid bedside diagnosis, showing translucent branching hyphae. * **Tinea Incognito:** Refers to a dermatophyte infection where the clinical appearance is altered (loss of active border) due to the inappropriate use of topical steroids. * **Deep Fungal Infections:** Unlike dermatophytes, subcutaneous fungi (like Sporotrichosis) or systemic fungi (like Histoplasmosis) involve the dermis and deeper tissues.

Question 84: Central clearing is a feature of which of the following conditions?

A. Lupus vulgaris
B. Tinea corporis (Correct Answer)
C. Leishmaniasis
D. All of the above

Explanation: **Explanation:** **Tinea corporis** (Dermatophytosis) is the correct answer because it characteristically presents as an **annular (ring-shaped) lesion**. The underlying medical concept involves the centrifugal spread of the fungus. The dermatophyte digests keratin as it moves outward, leading to an active, inflammatory, scaly border. As the infection progresses, the immune response or lack of nutrients in the center leads to resolution, resulting in the hallmark **central clearing**. **Analysis of Incorrect Options:** * **Lupus vulgaris:** This is a chronic form of cutaneous tuberculosis. It typically presents as reddish-brown "apple-jelly" nodules on diascopy. While it can show peripheral expansion, it usually results in **scarring and atrophy** rather than clear skin. * **Leishmaniasis:** Cutaneous leishmaniasis typically presents as an enlarging papule that progresses to a **crusted ulcer** with a raised "rolled" border. It does not exhibit the spontaneous central resolution seen in fungal infections. **High-Yield Clinical Pearls for NEET-PG:** * **KOH Mount:** The gold standard bedside test for Tinea corporis, showing translucent, branching, septate hyphae. * **Tinea Incognito:** Refers to a fungal infection where the classic annular morphology and central clearing are lost due to the application of topical steroids. * **Differential Diagnosis for Annular Lesions:** Remember the mnemonic **"SEGUE"**: **S**econdary syphilis, **E**rythema multiforme/annulare, **G**ranuloma annulare, **U**rticaria, and **E**czema (Nummular). * **Majocchi’s Granuloma:** A deep dermal fungal infection involving hair follicles, often caused by *T. rubrum*.

Question 85: Which of the following is true about Madura mycetoma?

A. It is a fungal infection.
B. It typically presents as a non-painful nodular lesion for many months.
C. It is characterized by discharging sinuses.
D. All of the above. (Correct Answer)

Explanation: **Explanation:** Madura mycetoma (Maduramycosis) is a chronic, granulomatous, inflammatory disease of the subcutaneous tissue, most commonly affecting the foot (Madura foot). It is characterized by a classic clinical triad: **localized swelling (nodules), multiple interconnecting discharging sinuses, and the presence of grains** in the discharge. * **Option A is true:** Mycetoma is classified into two types based on the causative agent: **Eumycetoma** (caused by true fungi like *Madurella mycetomatis*) and **Actinomycetoma** (caused by filamentous bacteria like *Nocardia* or *Actinomadura*). "Madura mycetoma" is often used synonymously with the fungal form. * **Option B is true:** The disease is notorious for its insidious onset and slow progression. It typically presents as a firm, painless subcutaneous nodule that persists for months or years. Pain is usually absent unless there is secondary bacterial infection or bone involvement. * **Option C is true:** As the lesion progresses, it forms abscesses that rupture to create multiple draining sinuses. These sinuses discharge serosanguinous fluid containing characteristic "grains" (colonies of the organism), which are diagnostic. **High-Yield Clinical Pearls for NEET-PG:** 1. **The Triad:** Tumefaction (swelling), Sinuses, and Grains. 2. **Grains:** Black grains are pathognomonic for **Eumycetoma** (*Madurella*). Yellow/White grains can be seen in both, but are more common in **Actinomycetoma**. 3. **Dot-in-a-Circle Sign:** A characteristic MRI finding where small high-intensity foci (grains) are surrounded by low-intensity rims. 4. **Treatment:** Actinomycetoma responds well to antibiotics (e.g., **Welsh Regime** using Amikacin and Cotrimoxazole). Eumycetoma is harder to treat, requiring long-term antifungals (Itraconazole) and often surgical debridement.

Question 86: A 30-year-old female presents with a history of itching under her right breast. On examination, an annular ring lesion was present under the breast. What is the most likely diagnosis?

A. Trichophyton rubrum (Correct Answer)
B. Candida albicans
C. Epidermophyton
D. Microsporum

Explanation: **Explanation:** The clinical presentation of an **annular (ring-shaped) lesion** with central clearing and an active, itchy border is the hallmark of **Tinea corporis** (Dermatophytosis). In the context of skin folds (like under the breast), it is often referred to as Tinea intertriginosa. **1. Why Trichophyton rubrum is correct:** *Trichophyton rubrum* is the most common cause of dermatophytosis worldwide. It typically presents as classical "ringworm"—erythematous, scaly, annular plaques with centrifugal spread. It is the leading pathogen for Tinea corporis, Tinea cruris, and Tinea pedis. **2. Why other options are incorrect:** * **Candida albicans:** While common in submammary folds (Intertrigo), it typically presents as **beefy red plaques** with **satellite lesions** (pustules) and lacks the clear central sparing seen in annular ring lesions. * **Epidermophyton:** *E. floccosum* can cause Tinea corporis/cruris, but it is less common than *T. rubrum* and **never involves the hair or nails** (unlike Trichophyton). * **Microsporum:** Species like *M. canis* or *M. audouinii* primarily cause **Tinea capitis** (scalp infections) in children. While they can cause body lesions, they are not the most frequent cause in an adult female. **Clinical Pearls for NEET-PG:** * **Most common dermatophyte overall:** *Trichophyton rubrum*. * **Wood’s Lamp:** Dermatophytes generally do not fluoresce, except for certain *Microsporum* species (Green fluorescence). * **Diagnosis:** KOH mount showing **septate branching hyphae**. * **Culture:** Sabouraud’s Dextrose Agar (SDA) is the standard medium. * **Treatment:** Topical azoles or terbinafine are first-line for localized Tinea corporis.

Question 87: A 30-year-old nurse, whose job requires frequent hand washing, has noted a small erosive skin lesion between the third interdigital web of her right hand. What is the best therapy for this condition?

A. Topical 5-fluorouracil
B. Topical clotrimazole (Correct Answer)
C. Oral griseofulvin
D. Topical hydrocortisone

Explanation: ### Explanation **Diagnosis: Erosio Interdigitalis Blastomycetica (EIB)** The clinical presentation describes **Erosio Interdigitalis Blastomycetica**, a localized form of cutaneous candidiasis typically caused by *Candida albicans*. It characteristically affects the third interdigital web space (the narrowest space) and is common in individuals whose occupations involve frequent water immersion or hand washing (e.g., nurses, bartenders, housewives). The maceration of the skin allows the yeast to colonize, leading to an oval-shaped, erythematous erosion with a white, sodden border. **1. Why Topical Clotrimazole is Correct:** Since EIB is a fungal infection (Candidiasis), the primary treatment is a **topical antifungal** agent. Clotrimazole, an imidazole, is highly effective against *Candida* species. Keeping the area dry is also a crucial adjunctive measure. **2. Why Other Options are Incorrect:** * **Topical 5-fluorouracil:** This is a cytotoxic chemotherapy agent used for actinic keratoses or superficial basal cell carcinomas; it has no role in treating fungal infections. * **Oral griseofulvin:** While an antifungal, griseofulvin is effective only against **dermatophytes** (Tinea) and is **ineffective against Candida**. Furthermore, systemic therapy is rarely needed for localized interdigital lesions. * **Topical hydrocortisone:** Steroids may temporarily reduce inflammation but will worsen a fungal infection by suppressing the local immune response (Tinea incognito). **Clinical Pearls for NEET-PG:** * **Predisposing Factors:** Diabetes mellitus and hyperhidrosis are common systemic associations. * **Site Predilection:** The **3rd web space** is most commonly involved because it is the tightest space, promoting moisture retention. * **Differential Diagnosis:** Erythrasma (caused by *Corynebacterium minutissimum*), which shows **coral-red fluorescence** under Wood’s lamp, unlike Candidiasis. * **Microscopy:** KOH mount of EIB will show budding yeast cells and pseudohyphae.

Question 88: A 24-year-old male presents with a 6-month history of hypopigmented patches over his chest with mild itching. A KOH mount of skin scrapings shows characteristic microscopic findings. What is the most probable diagnosis?

A. Pityriasis alba
B. Candidiasis
C. Tinea corporis
D. Pityriasis versicolor (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Pityriasis versicolor** **Medical Concept:** Pityriasis versicolor (Tinea versicolor) is a superficial fungal infection caused by the lipophilic yeast **_Malassezia furfur_**. The fungus produces **azelaic acid**, which inhibits tyrosinase, leading to decreased melanin production and the characteristic **hypopigmented patches** (though they can also be hyperpigmented or erythematous). The diagnosis is confirmed via a **KOH mount**, which reveals the classic **"Spaghetti and Meatballs" appearance** (short, thick hyphae and clusters of spores). **Why other options are incorrect:** * **A. Pityriasis alba:** Typically seen in children with atopy. It presents as ill-defined hypopigmented patches with fine scaling on the face. KOH mount is negative as it is not a fungal infection. * **B. Candidiasis:** Usually presents in intertriginous areas (skin folds) as bright red (erythematous) plaques with characteristic **satellite lesions**. It is painful or itchy, not typically hypopigmented. * **C. Tinea corporis:** Presents as an annular (ring-shaped) lesion with **central clearing** and an active, scaly border. While it shows hyphae on KOH, the clinical morphology differs from the diffuse patches of versicolor. **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp Examination:** Shows a characteristic **Golden-yellow fluorescence**. * **Sign of Besnier (Coup d'ongle sign):** Scratching the surface of the lesion produces fine, branny (furfuraceous) scales. * **Predisposing factors:** High humidity, sweating, and oily skin. * **Treatment:** Topical ketoconazole or selenium sulfide. Oral fluconazole/itraconazole for extensive cases.

Question 89: All of the following statements about thrush are true EXCEPT?

A. It is caused by a gram-negative fungus (Correct Answer)
B. It is characterized by a plaque of proliferating epithelial and other cells
C. It is a complication of immunosuppression or systemic disease
D. It can affect neonates in an epidemic fashion

Explanation: **Explanation:** **1. Why Option A is the correct (False) statement:** Thrush is caused by *Candida albicans*, which is a **Gram-positive** yeast. In microbiology, all fungi, including *Candida*, stain Gram-positive because their thick cell walls (containing chitin and glucans) retain the crystal violet dye. Therefore, the statement that it is caused by a "gram-negative fungus" is scientifically incorrect. **2. Analysis of other options:** * **Option B:** Oral thrush (pseudomembranous candidiasis) is characterized by creamy white "curd-like" plaques. These plaques consist of a dense network of fungal hyphae, pseudohyphae, proliferating desquamated epithelial cells, bacteria, and fibrin. * **Option C:** *Candida* is an opportunistic pathogen. Thrush is frequently seen in patients with compromised immunity (HIV/AIDS), those using inhaled corticosteroids, or those with systemic diseases like Diabetes Mellitus. * **Option D:** Neonatal thrush can occur during birth (via the maternal vaginal canal) or spread in nurseries. In institutional settings, it can indeed occur in an epidemic fashion due to cross-contamination via the hands of healthcare workers or contaminated feeding equipment. **High-Yield Clinical Pearls for NEET-PG:** * **The "Scrape" Test:** Unlike leukoplakia, the white plaques of oral thrush **can be scraped off**, leaving behind an erythematous, bleeding base. * **Morphology:** On KOH mount, *Candida* shows budding yeast cells and **pseudohyphae**. * **Drug of Choice:** For mild oral thrush, topical **Clotrimazole** or **Nystatin** suspension is used. For systemic or refractory cases, **Fluconazole** is the preferred agent. * **Risk Factor:** Chronic use of broad-spectrum antibiotics predisposes patients to thrush by altering the normal oral flora.

Question 90: A patient presented with scaly, hypopigmented and irregular macules on trunk and proximal extremities. Such a case is best treated with?

A. Amphotericin B
B. Itraconazole (Correct Answer)
C. Ciprofloxacin
D. Dapsone

Explanation: ### Explanation **Diagnosis: Pityriasis Versicolor (Tinea Versicolor)** The clinical presentation of scaly, hypopigmented, and irregular macules on the trunk and proximal extremities is classic for **Pityriasis Versicolor**. This is a superficial fungal infection caused by the lipophilic yeast *Malassezia furfur*. **1. Why Itraconazole is Correct:** Pityriasis Versicolor is a fungal infection. While topical antifungals (like Ketoconazole or Selenium sulfide) are first-line for localized cases, **systemic oral antifungals** like **Itraconazole** (200 mg daily for 5–7 days) or Fluconazole are highly effective for extensive or recurrent infections. Itraconazole works by inhibiting the enzyme 14α-demethylase, disrupting fungal cell membrane synthesis. **2. Why Other Options are Incorrect:** * **Amphotericin B:** This is a potent intravenous antifungal reserved for life-threatening systemic fungal infections (e.g., Mucormycosis, Cryptococcal meningitis). It is too toxic and unnecessary for a superficial infection like Pityriasis Versicolor. * **Ciprofloxacin:** This is a fluoroquinolone antibiotic used to treat bacterial infections. It has no activity against fungi or yeasts. * **Dapsone:** This is primarily used in the treatment of Leprosy and Dermatitis Herpetiformis. It is not an antifungal agent. **3. High-Yield Clinical Pearls for NEET-PG:** * **Causative Agent:** *Malassezia furfur* (formerly *Pityrosporum ovale*). * **Microscopy:** KOH mount shows a characteristic **"Spaghetti and Meatballs"** appearance (hyphae and blastospores). * **Wood’s Lamp:** Shows a characteristic **Golden-Yellow** (or pale yellow) fluorescence. * **Clinical Sign:** **Besnier’s Sign** (Scratch sign) – fine scaling becomes visible upon scratching the lesion. * **Note on Griseofulvin:** It is **ineffective** in Pityriasis Versicolor; it only works on dermatophytes.

Practice by Chapter

Dermatophytoses

Practice Questions

Tinea Versicolor

Practice Questions

Candidiasis

Practice Questions

Onychomycosis

Practice Questions

Subcutaneous Mycoses

Practice Questions

Systemic Mycoses with Cutaneous Manifestations

Practice Questions

Opportunistic Fungal Infections

Practice Questions

Mycetoma

Practice Questions

Tropical Fungal Infections

Practice Questions

Diagnosis of Fungal Infections

Practice Questions

Antifungal Therapy

Practice Questions

Preventive Strategies

Practice Questions

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