Fungal Skin Infections Practice Questions

Q: A 60-year-old woman complains to a physician because several of her toenails are discolored. Physical examination demonstrates crumbling, friable nails with distal-lateral separation from the nail bed. Hyperkeratotic debris is present under the affected part of the nail. Which of the following is the most likely pathogen?

Trichophyton. **Explanation:** The clinical presentation described—discolored, crumbling, friable nails with distal-lateral separation (onycholysis) and subungual hyperkeratosis—is a classic description of **Onychomycosis**, specifically the **Distal Lateral Subungual Onychomycosis (DLSO)** variant. **1. Why Trichophyton is correct:** Dermatophytes are the most common cause of onychomycosis worldwide (responsible for ~90% of cases). Among these, **_Trichophyton rubrum_** is the most frequent pathogen, followed by _Trichophyton mentagrophytes_. These fungi possess keratinolytic enzymes that allow them to invade and thrive in the keratinized tissue of the nail plate and bed. **2. Why the other options are incorrect:** * **Candida:** While *Candida* can cause onychomycosis, it typically presents as **Chronic Mucocutaneous Candidiasis** or is associated with **Paronychia** (inflammation of the nail fold), which is absent here. It more commonly affects fingernails in patients with frequent water exposure. * **Aspergillus & Mucor:** These are non-dermatophytic molds. While *Aspergillus* can occasionally cause secondary nail infections, it is much less common than *Trichophyton*. *Mucor* is an opportunistic fungus that typically causes invasive rhino-cerebral or pulmonary infections in immunocompromised patients, not isolated nail dystrophy. **Clinical Pearls for NEET-PG:** * **Most common cause of Onychomycosis:** *Trichophyton rubrum*. * **Gold Standard Diagnosis:** KOH mount (shows fungal hyphae) and Fungal Culture (Sabouraud’s Dextrose Agar). * **Drug of Choice:** **Oral Terbinafine** (250mg/day) for 6 weeks (fingernails) or 12 weeks (toenails). * **White Superficial Onychomycosis:** Characterized by "powdery" white patches on the nail surface, often caused by *T. mentagrophytes*. * **Proximal Subungual Onychomycosis:** Often a clinical marker for **HIV/AIDS**.

Q: A 60-year old male presented with discoloration, thickening, and tunneling of 2 fingernails and one toenail. Which of the following investigations will clinch the diagnosis at the earliest?

KOH mount. **Explanation:** The clinical presentation of nail discoloration, thickening (subungual hyperkeratosis), and tunneling (onycholysis) in an elderly patient is highly suggestive of **Onychomycosis** (Tinea unguium). **1. Why KOH Mount is correct:** Potassium Hydroxide (KOH) mount is the **gold standard initial investigation** for fungal skin and nail infections. KOH acts as a keratolytic agent, dissolving the keratin (skin/nail debris) and allowing for the clear visualization of fungal elements like hyphae, spores, or pseudohyphae under a microscope. It is rapid, cost-effective, and provides immediate confirmation of a fungal etiology, making it the investigation that clinches the diagnosis at the earliest. **2. Why other options are incorrect:** * **Wood’s Lamp:** Primarily used for diagnosing certain superficial infections like Tinea versicolor (golden yellow fluorescence) or Erythrasma (coral red). It is not useful for onychomycosis as most dermatophytes causing nail infections do not fluoresce. * **Slit Smear:** This is the diagnostic test for **Leprosy** (to detect *M. leprae*) and Leishmaniasis. It has no role in fungal nail pathology. * **Gram Stain:** Used for identifying **bacteria** (Gram-positive/negative). While it can occasionally show *Candida*, it is not the standard or most efficient method for diagnosing dermatophytic nail infections. **Clinical Pearls for NEET-PG:** * **Most common cause of Onychomycosis:** *Trichophyton rubrum*. * **Culture:** Sabouraud Dextrose Agar (SDA) is used for definitive species identification but takes 2–3 weeks (not the "earliest"). * **Treatment of Choice:** Oral **Terbinafine** is the first-line systemic agent for dermatophytic onychomycosis. * **Periodic Acid-Schiff (PAS) stain:** If KOH is negative but clinical suspicion is high, a nail clip biopsy with PAS stain is the most sensitive diagnostic method.

Q: A 30-year-old factory worker developed itchy, annular, scaly plaques in both groins that are extending peripherally. What is the most likely diagnosis?

Tinea cruris. ### Explanation **Correct Answer: C. Tinea cruris** **Why it is correct:** The clinical presentation of **itchy, annular (ring-shaped), scaly plaques** in the groin is classic for **Tinea cruris** (Jock itch). This is a dermatophyte infection, most commonly caused by *Trichophyton rubrum*. The hallmark of tinea is the **active border**—where the inflammation and scaling are most prominent at the periphery while the center shows "central clearing." The groin is a high-risk site due to heat, friction, and maceration, especially in manual laborers. **Why the other options are incorrect:** * **Granuloma annulare:** While annular, these lesions are typically **non-scaly** and asymptomatic. They are dermal papules arranged in a ring, often associated with diabetes mellitus. * **Annular lichen planus:** This presents as violaceous, flat-topped, polygonal papules. While it can be annular, it lacks the characteristic fine scaling of a fungal infection and usually shows **Wickham striae**. * **Erythema annulare centrifugum (EAC):** This is a reactive erythema. While it features "trailing scale" (scaling inside the advancing edge), it is less common than Tinea and usually lacks the intense pruritus and specific groin localization seen here. **NEET-PG High-Yield Pearls:** 1. **Diagnostic Gold Standard:** Potassium Hydroxide (**KOH**) mount showing translucent, branching, septate hyphae. 2. **The "Two Feet-One Hand" Syndrome:** Tinea cruris is often associated with Tinea pedis; always check the feet to prevent recurrence. 3. **Treatment:** Topical antifungals (e.g., Clotrimazole, Terbinafine) are first-line. **Avoid topical steroids**, as they lead to *Tinea incognito* (loss of typical features). 4. **Differential:** Erythrasma (caused by *Corynebacterium minutissimum*) also affects the groin but shows **coral-red fluorescence** under Wood’s lamp and lacks a central clearing.

Q: Which of the following is the drug of choice for sporotrichosis?

Itraconazole. **Explanation:** **Sporotrichosis**, also known as "Rose Gardener’s Disease," is a subcutaneous mycosis caused by the dimorphic fungus *Sporothrix schenckii*. It typically presents as a linear chain of nodules following lymphatic drainage (lymphocutaneous type) after traumatic inoculation from soil or plants. **1. Why Itraconazole is the Correct Answer:** **Itraconazole** is the current **drug of choice** for all forms of cutaneous and lymphocutaneous sporotrichosis. It is preferred due to its high efficacy, superior safety profile, and better tolerability compared to older treatments. The standard regimen is 200 mg daily for 3–6 months (continued for 2–4 weeks after lesions resolve). **2. Why the Other Options are Incorrect:** * **Ketoconazole & Miconazole:** These are older azoles. Ketoconazole is rarely used systemically due to risks of hepatotoxicity and inhibition of steroidogenesis (leading to gynecomastia). Miconazole is primarily used topically and is ineffective for systemic subcutaneous infections. * **Amphotericin B:** While highly potent, it is reserved only for **disseminated or systemic sporotrichosis** and cases involving pregnancy, as it is too toxic for localized cutaneous disease. **3. High-Yield Clinical Pearls for NEET-PG:** * **Historical Drug of Choice:** Saturated Solution of Potassium Iodide (**SSKI**) was the traditional treatment. While still an option (especially in resource-limited settings), it has been replaced by Itraconazole due to side effects like iodism and metallic taste. * **Asteroid Bodies:** Histopathology often shows the "Splendore-Hoeppli phenomenon" (eosinophilic material surrounding the yeast). * **Culture:** The gold standard for diagnosis. At 25°C, it shows a characteristic "flowerette" or "daisy-like" arrangement of conidia. * **Fixed Cutaneous Sporotrichosis:** A variant presenting as a single ulcerated plaque at the site of inoculation without lymphatic spread.

Q: A 26-year-old male presents to the OPD complaining of hair loss and itching on the scalp. Physical examination reveals moderate patchy hair loss from the central portion of the scalp, and the lesions have a ring-like configuration with central clearing. Which of the following drugs can be used to treat this patient's condition?

Terbinafine. **Explanation:** **Diagnosis:** The clinical presentation of patchy hair loss, itching, and ring-like lesions with central clearing on the scalp is characteristic of **Tinea Capitis** (a dermatophyte infection). **Why Terbinafine is Correct:** Tinea capitis requires **systemic antifungal therapy** because topical agents cannot penetrate the hair follicle deeply enough to eradicate the fungus. **Terbinafine** is a first-line systemic antifungal (an allylamine) that inhibits the enzyme *squalene epoxidase*, leading to a deficiency in ergosterol and a toxic buildup of squalene, which is fungicidal. While Griseofulvin was historically the gold standard, Terbinafine is now preferred for *Trichophyton* species. **Why Other Options are Incorrect:** * **A. Local Corticosteroids:** These are contraindicated. Applying steroids to a fungal infection can lead to *Tinea Incognito*, where the inflammation is suppressed but the fungus flourishes, worsening the infection. * **B. Progesterone:** This is a hormone with no role in treating fungal infections or standard hair loss. * **C. Finasteride:** This is a 5-alpha-reductase inhibitor used for **Androgenetic Alopecia** (male pattern baldness). It does not treat infectious causes of hair loss and would not address the itching or ring-like lesions. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Griseofulvin is still often considered the DOC for *Microsporum* species, while Terbinafine is superior for *Trichophyton* (the most common cause worldwide). * **Black Dot Tinea:** Caused by endothrix organisms (e.g., *T. tonsurans*), where hair breaks at the surface. * **Grey Patch Tinea:** Caused by ectothrix organisms (e.g., *M. audouinii*), showing scaling and dull grey hair. * **Kerion:** A painful, inflammatory boggy swelling; requires systemic antifungals plus/minus steroids to prevent scarring.

Q: Which of the following is NOT a feature of Tinea capitis?

Most commonly occurs in the elderly. **Explanation:** **Tinea capitis** is a fungal infection of the scalp hair and skin. The correct answer is **Option B** because Tinea capitis is primarily a disease of **children** (pre-pubertal age). It is rarely seen in adults/elderly because post-pubertal sebum contains **fungistatic medium-chain fatty acids** that inhibit dermatophyte growth. **Analysis of other options:** * **Option A (Boggy swelling):** This refers to **Kerion**, an inflammatory variant of Tinea capitis caused by a hypersensitivity reaction to zoophilic fungi. It presents as a painful, boggy, inflammatory mass with pustules and crusting. * **Option C (Black dot):** This is a characteristic clinical presentation where the hair breaks off at the scalp surface due to **endothrix** infection (e.g., *T. tonsurans*), leaving behind "black dots" (the distal ends of broken hair shafts). * **Option D (Causative organisms):** Tinea capitis is caused by species of **Trichophyton** and **Microsporum**. Crucially, **Epidermophyton floccosum** does NOT cause Tinea capitis as it does not invade hair (it only affects skin and nails). **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause worldwide:** *Trichophyton tonsurans* (Endothrix). * **Most common cause in India:** *Trichophyton violaceum*. * **Wood’s Lamp Examination:** *Microsporum* species show a **bright green** fluorescence, while *Trichophyton* (except *T. schoenleinii*) usually does not fluoresce. * **Drug of Choice:** **Oral Griseofulvin** remains the gold standard for Tinea capitis (Terbinafine is also used, especially for *Trichophyton*). Topical antifungals are ineffective as they do not penetrate the hair follicle.

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.

Question 1

A 60-year-old woman complains to a physician because several of her toenails are discolored. Physical examination demonstrates crumbling, friable nails with distal-lateral separation from the nail bed. Hyperkeratotic debris is present under the affected part of the nail. Which of the following is the most likely pathogen?

Accepted Answer

Trichophyton

Answer

Aspergillus

Answer

Candida

Answer

Mucor

Question 2

Which agent is used in the treatment of oral thrush?

Accepted Answer

Clotrimazole

Answer

Miconazole

Answer

Clobetasol

Answer

Amoxycillin

Question 3

A 45-year-old woman presents with thick, yellow toenails. She is otherwise healthy and takes no medications. Examination reveals affected toenails on her right foot and the great toenail on her left foot. There is no periungual erythema, and her peripheral pulses are good. What is the best advice for this patient?

Accepted Answer

Oral antifungal therapies will be required for several months until the affected nails have completely grown out.

Answer

This nail condition is likely to resolve spontaneously.

Answer

Laboratory tests including CBC, comprehensive metabolic profile, chest x-ray, and abdominal CT scan should be ordered to rule out underlying malignancy.

Answer

Nail sampling is not necessary for making a definitive diagnosis.

Question 4

A 60-year old male presented with discoloration, thickening, and tunneling of 2 fingernails and one toenail. Which of the following investigations will clinch the diagnosis at the earliest?

Accepted Answer

KOH mount

Answer

Wood's lamp examination

Answer

Slit smear (split skin smear)

Answer

Gram stain

Question 5

A 30-year-old factory worker developed itchy, annular, scaly plaques in both groins that are extending peripherally. What is the most likely diagnosis?

Accepted Answer

Tinea cruris

Answer

Granuloma annulare

Answer

Annular lichen planus

Answer

Erythema annulare centrifugum

Question 6

Which of the following is the drug of choice for sporotrichosis?

Accepted Answer

Itraconazole

Answer

Ketoconazole

Answer

Miconazole

Answer

Amphotericin - B

Question 7

A 26-year-old male presents to the OPD complaining of hair loss and itching on the scalp. Physical examination reveals moderate patchy hair loss from the central portion of the scalp, and the lesions have a ring-like configuration with central clearing. Which of the following drugs can be used to treat this patient's condition?

Accepted Answer

Terbinafine

Answer

Local corticosteroid

Answer

Progesterone

Answer

Finasteride

Question 8

Which of the following is NOT a feature of Tinea capitis?

Accepted Answer

Most commonly occurs in the elderly

Answer

May present as a boggy swelling

Answer

May present as black dot

Answer

Caused by Trichophyton and Microsporum, but not by Epidermophyton

Question 9

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 10

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

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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