Fungal Skin Infections Practice Questions

Q: A 19-year-old man develops a rash in the groin area. On examination, it is a large well-demarcated area of tan-brown discoloration around his left inguinal area. There is some scaling of the lesion when brushed with a tongue depressor. Which of the following is the most appropriate initial diagnostic test?

Potassium hydroxide (KOH) preparation of scrapings. ### Explanation The clinical presentation of a **well-demarcated, tan-brown, scaling lesion** in the inguinal area of a young male is highly suggestive of a superficial fungal infection, most commonly **Tinea cruris** (jock itch). **1. Why KOH Preparation is the Correct Answer:** The initial diagnostic step for any scaling skin lesion suspected of being fungal is a **Potassium Hydroxide (KOH) preparation**. KOH dissolves the keratinocytes, allowing for the clear visualization of fungal elements (septate hyphae and spores) under a microscope. It is a rapid, bedside, and cost-effective test that confirms the diagnosis before starting antifungal therapy. **2. Analysis of Incorrect Options:** * **Punch biopsy (A):** This is an invasive procedure reserved for atypical presentations, suspected malignancies, or inflammatory dermatoses that do not respond to treatment. It is not an initial test for a scaling groin rash. * **Tzanck smear (B):** This is used for the diagnosis of **herpetic infections** (HSV/VZV) to look for multinucleated giant cells. It is not used for fungal infections. * **Blood culture (D):** This is used for systemic or disseminated fungal infections (e.g., Candidemia). Superficial dermatophyte infections are localized to the stratum corneum and do not cause fungemia. **3. NEET-PG High-Yield Pearls:** * **Differential Diagnosis:** A major differential for this presentation is **Erythrasma** (caused by *Corynebacterium minutissimum*). While both appear brown and scaly, Erythrasma shows a characteristic **coral-red fluorescence** under a **Wood’s lamp**. * **Tinea Cruris vs. Candidiasis:** Tinea cruris typically **spares the scrotum**, whereas Inguinal Candidiasis often involves the scrotum and presents with **satellite lesions**. * **Clinical Sign:** The "scaling when brushed" mentioned in the prompt refers to the **"accentuation of scales"** seen in fungal infections.

Q: A 12-year-old boy presents with a boggy swelling and easily pluckable hair. What is the probable diagnosis?

Tinea capitis. ### Explanation **Correct Answer: B. Tinea capitis** The clinical presentation of a **boggy, inflammatory swelling** with **easily pluckable hair** is the classic description of a **Kerion**, which is a severe inflammatory form of **Tinea capitis**. * **Pathophysiology:** Tinea capitis is a dermatophyte infection of the scalp, most common in children. A Kerion represents a delayed-type hypersensitivity reaction to the fungus (commonly *Trichophyton verrucosum* or *T. mentagrophytes*). * **Clinical Features:** The "boggy" nature refers to the soft, pus-filled, abscess-like consistency. Hair follicles are damaged by the intense inflammation, leading to hair that can be pulled out without pain (easily pluckable). **Why other options are incorrect:** * **Lichen planus:** Specifically, Lichen Planopilaris causes scarring alopecia with perifollicular scaling and erythema, but it does not present as a boggy, acute inflammatory mass. * **Epidermophytosis:** While *Epidermophyton* is a dermatophyte, it typically affects the skin (Tinea corporis/cruris) and nails, but **never** infects the hair. * **Alopecia areata:** This presents as non-scarring, non-inflammatory smooth patches of hair loss. The characteristic finding is "exclamation mark hair," not a boggy swelling. **High-Yield NEET-PG Pearls:** 1. **Kerion Management:** Do **not** incise and drain (it is not a bacterial abscess). Treat with systemic antifungals (Griseofulvin is the gold standard) and sometimes oral steroids to reduce scarring. 2. **Black Dot Tinea:** Caused by endothrix organisms (e.g., *T. tonsurans*); hair breaks at the surface. 3. **Favus:** Caused by *T. schoenleinii*; characterized by **scutula** (cup-shaped crusts) and a "mousy odor." 4. **Wood’s Lamp:** *Microsporum* species show a brilliant green fluorescence, while most *Trichophyton* species (except *T. schoenleinii*) do not fluoresce.

Q: Which of the following statements about pityriasis versicolor is FALSE?

Corticosteroids are used in its treatment.. ### Explanation **Pityriasis Versicolor (Tinea Versicolor)** is a superficial fungal infection caused by the lipophilic yeast *Malassezia*. **Why Option D is the Correct (False) Statement:** Corticosteroids are **contraindicated** in fungal infections. They are immunosuppressive agents that can worsen the infection, lead to its spread, or mask symptoms (Tinea Incognito). The mainstay of treatment for Pityriasis Versicolor includes **topical antifungals** (e.g., Ketoconazole shampoo, Ciclopirox olamine) or oral antifungals (e.g., Fluconazole, Itraconazole) for extensive cases. **Analysis of Other Options:** * **Option A:** While *Malassezia furfur* was historically cited, **_Malassezia globosa_** is now recognized as the most common causative agent. * **Option B:** A KOH mount of skin scrapings reveals short, thick hyphae and clusters of spores, classically described as a **"spaghetti and meatball"** or "banana and grapes" appearance. * **Option C:** *Malassezia* is lipophilic and requires the addition of olive oil to SDA for growth. The resulting colonies are creamy/yellowish and often exhibit a characteristic **"fried egg"** morphology. **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp Examination:** Shows a characteristic **yellowish-gold or pale-yellow fluorescence**. * **Clinical Presentation:** Hypopigmented or hyperpigmented macules with fine scaling (**Besnier’s sign** or "scratch sign"—scaling becomes visible upon scratching the lesion). * **Pathogenesis:** The hypopigmentation is due to **azelaic acid** produced by the fungus, which inhibits tyrosinase, thereby interfering with melanin synthesis. * **Common Site:** Upper trunk and back (seborrheic areas).

Q: An 8-year-old boy presents with a boggy scalp swelling and easily pluckable hair. Which of the following is the investigation of choice?

KOH smear. ### Explanation **Diagnosis: Kerion (Inflammatory Tinea Capitis)** The clinical presentation of a **boggy, painful scalp swelling** with **easily pluckable hair** and associated lymphadenopathy is classic for **Kerion**. This is a severe inflammatory cell-mediated immune response to a dermatophyte infection (most commonly *Trichophyton mentagrophytes* or *T. verrucosum*). **Why KOH Smear is the Correct Answer:** * **Investigation of Choice:** In any suspected fungal infection of the skin, hair, or nails, a **10%–20% KOH (Potassium Hydroxide) smear** is the initial and most important investigation. * **Mechanism:** KOH dissolves keratin, allowing the visualization of fungal elements. In Kerion, microscopic examination of the plucked hair will show fungal hyphae or spores (ectothrix or endothrix invasion), confirming the dermatophytic origin. **Why Other Options are Incorrect:** * **A. Biopsy:** Rarely indicated for tinea capitis. It is invasive and usually reserved for cases where inflammatory conditions like discoid lupus or lichen planopilaris are suspected. * **B. X-ray Skull:** Kerion is a soft tissue fungal infection; it does not involve the bone. X-rays have no diagnostic value here. * **D. Tzanck Smear:** This is used for the rapid diagnosis of **Herpes Simplex or Varicella-Zoster** (looking for multinucleated giant cells), not fungal infections. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** Oral **Griseofulvin** is the gold standard for Tinea Capitis (Kerion). Topical antifungals are ineffective as they do not penetrate the hair follicle. * **Complication:** If untreated, Kerion leads to **cicatricial (permanent) alopecia**. * **Wood’s Lamp:** Useful for screening; *Microsporum* species show a brilliant green fluorescence, while most *Trichophyton* species (common in Kerion) do not fluoresce.

Q: 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?

Trichophyton rubrum. **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.

Q: 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?

Pityriasis versicolor. ### 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.

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

Itraconazole. ### 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.

Q: All of the following are true regarding Tinea versicolor except:

Griseofulvin is the drug of choice. **Explanation:** **Tinea versicolor** (Pityriasis versicolor) is a common superficial fungal infection caused by the lipophilic yeast **Malassezia globosa** (and *M. furfur*). **Why Option C is the correct answer (False statement):** Griseofulvin is **ineffective** in the treatment of Tinea versicolor. Griseofulvin is only active against dermatophytes (Trichophyton, Microsporum, and Epidermophyton) because it requires active keratin uptake, which Malassezia does not perform. The **drug of choice** for localized infection is topical ketoconazole or selenium sulfide; for systemic treatment, oral **Itraconazole** or Fluconazole is preferred. **Analysis of other options:** * **Option A:** Under Wood’s lamp, the lesions typically show a characteristic **golden-yellow or orange fluorescence** due to the presence of pteridine metabolites. * **Option B:** While *M. furfur* was historically cited, **Malassezia globosa** is now recognized as the most common causative agent. * **Option D:** The name "versicolor" refers to the variety of pigmentary changes. It can present as **hypopigmented** (due to azelaic acid production inhibiting melanin) or **hyperpigmented/erythematous** lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Microscopy:** KOH mount shows the classic **"Spaghetti and Meatballs"** appearance (short, thick hyphae and clusters of spores). * **Clinical Sign:** **Besnier’s sign** (or "Coupe d’ongle" sign) – scratching the lesion produces fine, branny scales. * **Culture:** Requires enrichment with lipids (e.g., olive oil) as Malassezia is lipophilic. * **Risk Factors:** High humidity, excessive sweating, and oily skin.

Question 1

A 19-year-old man develops a rash in the groin area. On examination, it is a large well-demarcated area of tan-brown discoloration around his left inguinal area. There is some scaling of the lesion when brushed with a tongue depressor. Which of the following is the most appropriate initial diagnostic test?

Accepted Answer

Potassium hydroxide (KOH) preparation of scrapings

Answer

Punch biopsy of skin

Answer

Tzanck smear

Answer

Blood culture for fungi

Question 2

A 12-year-old boy presents with a boggy swelling and easily pluckable hair. What is the probable diagnosis?

Accepted Answer

Tinea capitis

Answer

Lichen planus

Answer

Epidermophytosis

Answer

Alopecia areata

Question 3

Which of the following statements about pityriasis versicolor is FALSE?

Accepted Answer

Corticosteroids are used in its treatment.

Answer

It is caused by Malassezia globosa.

Answer

It shows a 'spaghetti and meatball' appearance on KOH mount.

Answer

Fungal colonies on Sabouraud Dextrose Agar (SDA) have a 'fried egg' appearance.

Question 4

Which of the following is NOT a true statement regarding Tinea capitis?

Accepted Answer

It is characterized by the presence of dark brown to black nodules cemented to the hair shaft.

Answer

It is a form of Tinea capitis.

Answer

It is caused by Tinea schoenlein.

Answer

It causes cicatricial alopecia.

Question 5

An 8-year-old boy presents with a boggy scalp swelling and easily pluckable hair. Which of the following is the investigation of choice?

Accepted Answer

KOH smear

Answer

Biopsy

Answer

X-ray skull

Answer

Tzank smear

Question 6

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?

Accepted Answer

Trichophyton rubrum

Answer

Candida albicans

Answer

Epidermophyton

Answer

Microsporum

Question 7

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?

Accepted Answer

Topical clotrimazole

Answer

Topical 5-fluorouracil

Answer

Oral griseofulvin

Answer

Topical hydrocortisone

Question 8

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?

Accepted Answer

Pityriasis versicolor

Answer

Pityriasis alba

Answer

Candidiasis

Answer

Tinea corporis

Question 9

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

Accepted Answer

Itraconazole

Answer

Amphotericin B

Answer

Ciprofloxacin

Answer

Dapsone

Question 10

All of the following are true regarding Tinea versicolor except:

Accepted Answer

Griseofulvin is the drug of choice

Answer

Orange fluorescence with Wood lamp examination

Answer

Caused by Malassezia globosa

Answer

Both hypo and hyperpigmented lesions

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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