Fungal Skin Infections Practice Questions

Q: A teenage girl presents with multiple white macules on her upper trunk, showing scaling on scraping. KOH mount of the lesions revealed a specific organism. What is the most likely causative agent?

Malassezia furfur. ### Explanation **Correct Answer: A. Malassezia furfur** The clinical presentation of **hypopigmented (white) macules** on the upper trunk with fine scaling is classic for **Pityriasis versicolor** (Tinea versicolor). The characteristic "scaling on scraping" is known as the **Besnier’s sign** (or scratch sign). **Medical Concept:** *Malassezia furfur* is a lipophilic yeast that forms part of the normal skin flora. Under hot and humid conditions, it converts to a pathogenic mycelial form. It produces **azelaic acid**, which inhibits tyrosinase, leading to decreased melanin production and the characteristic hypopigmentation. On a KOH mount, it shows the pathognomonic **"Spaghetti and Meatballs" appearance** (short hyphae and thick-walled spores). **Why Incorrect Options are Wrong:** * **B. Tinea rubrum:** The most common cause of dermatophytosis (Tinea corporis/cruris). It typically presents as erythematous, itchy, annular plaques with a central clearing and an active scaling border, not isolated white macules. * **C. Epidermophyton floccosum:** A dermatophyte that affects skin and nails (never hair). It causes Tinea cruris and pedis, characterized by maceration or scaly plaques, rather than hypopigmented trunk lesions. * **D. Candida albicans:** Typically presents in intertriginous areas (skin folds) as erythematous "beefy red" plaques with characteristic **satellite lesions** and pustules. **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp Examination:** Shows a characteristic **yellowish-gold fluorescence**. * **Microscopy:** KOH mount reveals short, curved hyphae and clusters of round yeast cells (Spaghetti and Meatballs). * **Treatment:** Topical antifungals (Ketoconazole shampoo, Selenium sulfide). Oral Fluconazole/Itraconazole is used for extensive cases. * **Culture:** Requires enrichment with lipids (e.g., olive oil) as *Malassezia* is lipophilic.

Q: A 16-year-old patient was recently diagnosed with HIV. Which of the following fungal nail infections could be associated?

Proximal subungual onychomycosis. **Explanation:** **Proximal Subungual Onychomycosis (PSO)** is the rarest form of onychomycosis in the general population but is considered a **pathognomonic clinical marker for HIV/AIDS** or other severe immunocompromised states. In PSO, the fungus (most commonly *Trichophyton rubrum*) invades the nail fold and moves distally under the proximal nail plate. This results in a characteristic white-to-beige discoloration starting at the lunula (the "half-moon" area). In immunocompetent individuals, the nail's protective cuticle and rapid growth usually prevent this route of infection; however, in HIV patients, the loss of T-cell-mediated immunity allows the fungus to bypass these barriers. **Analysis of Incorrect Options:** * **A. Distal Subungual Onychomycosis:** This is the **most common** type of fungal nail infection in the general population. While it can occur in HIV patients, it is not specifically "associated" with or highly suggestive of an underlying immunodeficiency. * **C. White Superficial Onychomycosis:** This involves direct invasion of the dorsal surface of the nail plate, appearing as "chalky white" patches. It is common in the general population and not a specific marker for HIV. * **D. Paronychia with Candida:** This is typically seen in individuals with frequent water exposure (e.g., cooks, laundry workers) or chronic mucocutaneous candidiasis, but it is not the classic presentation linked to HIV-related dermatophytosis. **High-Yield Clinical Pearls for NEET-PG:** * **PSO + HIV:** If you see PSO in a young patient, the next best step is to order an **HIV screening test**. * **Most common cause of Onychomycosis:** *Trichophyton rubrum*. * **Treatment of Choice:** Oral **Terbinafine** (250 mg/day) for 6 weeks (fingernails) or 12 weeks (toenails). * **Diagnosis:** Confirmed by **KOH mount** of nail clippings or fungal culture.

Q: The appearance of this foot is most consistent with which one of the following diagnoses?

Chromomycosis. ***Chromomycosis*** - Characterized by **verrucous, cauliflower-like lesions** on the foot, caused by dematiaceous fungi like **Fonsecaea pedrosoi** or **Cladophialophora carrionii**. - Diagnosis confirmed by finding **sclerotic bodies** (muriform cells) in tissue or KOH preparations, showing thick-walled, brown, septate cells. *Buruli ulcer* - Presents as **painless, necrotic ulcers** with undermined edges, not verrucous lesions, caused by **Mycobacterium ulcerans**. - Typically occurs in **tropical regions** near water bodies and progresses from nodules to large ulcerative lesions. *Leishmaniasis* - **Cutaneous leishmaniasis** presents as painless ulcers with **raised, indurated borders**, not cauliflower-like growths. - Caused by **Leishmania species** transmitted by **sandfly bites**, diagnosed by finding amastigotes in tissue samples. *Madura foot* - **Mycetoma** characterized by the triad of **tumefaction, sinuses, and grains** discharging from multiple openings. - Caused by either **actinomycetes** (actinomycetoma) or **true fungi** (eumycetoma), with grains varying in color depending on the causative organism.

Q: A patient presents with a non-itchy plaque positive for hyphae. What is the most likely diagnosis?

Tinea incognito. ### Explanation The correct answer is **Tinea incognito (Option C)**. **1. Why Tinea incognito is correct:** Tinea incognito refers to a dermatophytic infection that has lost its typical clinical features—specifically the **characteristic itching** and the **well-defined erythematous border**—due to the inappropriate application of topical corticosteroids. Steroids suppress the local inflammatory response, which masks the symptoms (making it "non-itchy") and alters the morphology of the lesion. However, the fungus continues to proliferate in the skin; therefore, a KOH mount will still show abundant **hyphae**, confirming the fungal etiology despite the atypical presentation. **2. Why the other options are incorrect:** * **Tinea corporis (Option B):** This is the classic "ringworm" of the body. It is characteristically **highly pruritic (itchy)** with a prominent, scaly, active border and central clearing. * **Tinea capitis (Option A):** This involves the scalp and hair follicles. While it shows hyphae/spores, it typically presents with alopecia, scaling, or inflammatory kerion, rather than a simple non-itchy plaque on the body. * **Tinea facei (Option D):** This refers to fungal infection of the face. Like tinea corporis, it is usually itchy and erythematous unless it has been modified by steroids (in which case it would also be classified as tinea incognito). **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Steroid Modified" Fungus:** Always suspect Tinea incognito when a "dermatitis-like" lesion fails to respond to steroids or worsens after an initial brief improvement. * **KOH Mount:** In Tinea incognito, the KOH mount often shows an **unusually high density of hyphae** because the steroid-induced local immunosuppression allows for unchecked fungal growth. * **Management:** Immediate cessation of steroids and initiation of systemic antifungal therapy (e.g., Itraconazole or Terbinafine).

Q: A thirty-two-year-old adult male presents with a chronic suppurative lesion on the angle of the jaw. Microscopic examination shows small abscesses immediately beneath the epidermis with moderate growth of epithelial cords. In the abscess, there are oval, unicellular organisms measuring 20 µm in diameter and having a thick, double-refractive cell wall and cytoplasm containing refractive granules and vacuoles. Which of the following is the most likely diagnosis?

Blastomycosis. **Explanation:** The clinical presentation and histopathology point directly to **Blastomycosis** (specifically North American Blastomycosis caused by *Blastomyces dermatitidis*). **1. Why Blastomycosis is correct:** * **Clinical Presentation:** Chronic suppurative or granulomatous lesions on the face (angle of the jaw) are characteristic of the cutaneous form. * **Histopathology:** The presence of **pseudoepitheliomatous hyperplasia** (described as "moderate growth of epithelial cords") and **intraepidermal/subepidermal microabscesses** are hallmark features. * **Morphology:** The "oval, unicellular organisms (20 µm) with a **thick, double-refractive cell wall**" and refractive granules describe the yeast form of *Blastomyces*. A key diagnostic feature (though not explicitly mentioned here) is the **broad-based budding** yeast. **2. Why other options are incorrect:** * **Foreign body reaction:** Would show multinucleated giant cells and foreign material under polarized light, but not specific unicellular organisms with double-refractive walls. * **Syphilis:** Primary syphilis (chancre) or secondary syphilis (condyloma lata) shows a dense plasma cell infiltrate and endarteritis, not microabscesses with 20 µm yeast cells. * **Tuberculosis (Lupus Vulgaris/Scrofuloderma):** Characterized by caseating granulomas and Acid-Fast Bacilli (AFB). While it can cause jaw lesions (Scrofuloderma), the specific yeast morphology and microabscesses rule it out. **High-Yield Clinical Pearls for NEET-PG:** * **Pseudoepitheliomatous Hyperplasia (PEH):** Often mimics Squamous Cell Carcinoma. It is commonly seen in Blastomycosis, Chromoblastomycosis, Donavanosis, and Lupus Vulgaris. * **Blastomyces Morphology:** Large (8–15 µm, up to 20 µm), broad-based budding, "double-contoured" appearance. * **Systemic Involvement:** Though cutaneous lesions are common, the primary site of infection is usually the **lungs** via inhalation.

Q: Which of the following tests is likely to be helpful in diagnosing a patient presenting with an itchy annular plaque on the face?

Potassium hydroxide mount. ### Explanation **Correct Answer: D. Potassium hydroxide (KOH) mount** The clinical presentation of an **itchy annular (ring-shaped) plaque** with central clearing and an active scaling border is a classic description of **Tinea faciei** (Dermatophytosis of the face). **Why KOH Mount is the Gold Standard:** Dermatophytes (such as *Trichophyton*, *Microsporum*, and *Epidermophyton*) invade the keratinized layers of the skin. A KOH mount is the initial investigation of choice because the alkali (10-20% KOH) dissolves the keratinocytes, allowing for the clear visualization of characteristic **translucent, branching, septate hyphae** under a microscope. **Analysis of Incorrect Options:** * **A. Gram's stain:** Primarily used for identifying bacterial infections (Gram-positive vs. Gram-negative). It is not used for diagnosing dermatophytosis. * **B. Tissue smear:** Usually refers to a Tzanck smear (used for Herpes Simplex/Varicella) or a slit-skin smear (used for Leprosy/Leishmaniasis). It does not demonstrate fungal hyphae effectively. * **C. Wood's lamp examination:** While useful for *Tinea capitis* (showing green fluorescence in *Microsporum* species) or *Erythrasma* (coral-red fluorescence), most cases of Tinea corporis/faciei caused by *Trichophyton rubrum* do not fluoresce, making it less reliable than a KOH mount. **Clinical Pearls for NEET-PG:** * **Tinea Incognito:** This occurs when a fungal infection is treated with topical steroids, leading to a loss of the classic annular morphology and making diagnosis difficult. * **Specimen Collection:** Always scrape scales from the **active peripheral margin** of the lesion, as this is where the fungal load is highest. * **Culture:** Sabouraud’s Dextrose Agar (SDA) is the standard culture medium for fungi, but it takes 2–3 weeks, making KOH the preferred rapid diagnostic tool.

Q: What is the management for the given case?

Antifungals treatment for oral candidiasis. ***Antifungals treatment for oral candidiasis*** - The white, creamy, **scrapable plaques** on oral mucosa are pathognomonic for **oral candidiasis (thrush)**. - **Topical antifungals** like nystatin or **systemic antifungals** like fluconazole are the standard first-line treatments. *Vitamin supplements* - Vitamin deficiencies may predispose to oral infections but do not treat the **active fungal infection** present. - **Nutritional supplementation** alone would not resolve the characteristic white plaques of candidiasis. *Stop smoking and screen for carcinoma* - This management is appropriate for **leukoplakia**, which presents as non-scrapable white patches with malignant potential. - **Oral candidiasis** is easily scrapable and has no direct association with **smoking** or **malignancy**. *Dapsone plus steroids* - This combination is used for **autoimmune blistering diseases** like pemphigus or **inflammatory conditions**. - **Oral candidiasis** is a **fungal infection** requiring antifungal therapy, not immunosuppressive treatment.

Q: Potassium iodide is useful in the treatment of which of the following conditions?

Sporotrichosis. **Explanation:** **Sporotrichosis** (Rose Gardener’s disease) is a subcutaneous fungal infection caused by the dimorphic fungus *Sporothrix schenckii*. Historically, **Saturated Solution of Potassium Iodide (SSKI)** has been the traditional drug of choice for the lymphocutaneous and fixed cutaneous forms of this infection. While Itraconazole is now considered the first-line treatment due to better tolerability, SSKI remains a highly effective and high-yield alternative in dermatological therapeutics. Its exact mechanism of action is not fully understood, but it is believed to act by enhancing the host’s immune response and inhibiting the fungal granulomatous reaction rather than acting as a direct antifungal. **Analysis of Incorrect Options:** * **Impetigo:** This is a superficial bacterial infection (usually *S. aureus* or *S. pyogenes*) treated with topical (Mupirocin) or systemic antibiotics. * **Viral Warts:** Caused by Human Papillomavirus (HPV), these are managed with destructive methods (cryotherapy, salicylic acid) or immunomodulators (Imiquimod). * **Dermatitis Herpetiformis:** This is an autoimmune blistering disorder associated with Celiac disease. The drug of choice is **Dapsone**, along with a gluten-free diet. **High-Yield Clinical Pearls for NEET-PG:** * **SSKI Side Effects:** Watch for "Iodism" (metallic taste, increased salivation, coryza, and frontal headache) and hypothyroidism (Wolff-Chaikoff effect). * **Other uses of Potassium Iodide:** It is also used in Erythema Nodosum and Sweet Syndrome (Neutrophilic dermatosis). * **Sporotrichosis Presentation:** Look for a history of trauma (thorn prick) followed by linear nodules along the lymphatics (**Sporotrichoid spread**).

Q: In dermatophytosis, which antifungal drug is not indicated?

Amphotericin B. **Explanation:** The correct answer is **Amphotericin B**. Dermatophytosis (Tinea) is a superficial fungal infection caused by fungi that colonize keratinized tissues (skin, hair, and nails). **1. Why Amphotericin B is the correct answer:** Amphotericin B is a potent polyene antifungal reserved for **systemic, life-threatening deep mycoses** (e.g., Mucormycosis, Cryptococcosis, Aspergillosis) and Visceral Leishmaniasis. It is administered intravenously and carries a high risk of nephrotoxicity. Because dermatophytes are confined to the superficial keratin layers, the systemic toxicity of Amphotericin B far outweighs any benefit, making it inappropriate and unnecessary for these infections. **2. Analysis of incorrect options:** * **Terbinafine (Allylamine):** Currently the **drug of choice** for most dermatophytoses. It is fungicidal and works by inhibiting the enzyme squalene epoxidase. * **Griseofulvin:** A fungistatic drug that binds to polymerized microtubules, disrupting mitosis. It was historically the gold standard for Tinea capitis (especially *Microsporum* species). * **Fluconazole (Azole):** An oral triazole that inhibits 14-alpha-demethylase. While often second-line to Terbinafine, it is an effective and indicated treatment for various forms of Tinea. **NEET-PG High-Yield Pearls:** * **Mechanism of Action:** Terbinafine inhibits **Squalene Epoxidase**; Azoles inhibit **14-α-demethylase**. * **Tinea Capitis:** Griseofulvin is still highly effective, but Terbinafine is preferred for *Trichophyton* infections. * **Onychomycosis:** Oral Terbinafine is the first-line systemic treatment. * **Amphotericin B Side Effect:** Most common acute side effect is "shake and bake" (fever/chills); most serious long-term side effect is **nephrotoxicity** (renal tubular acidosis).

Question 1

A teenage girl presents with multiple white macules on her upper trunk, showing scaling on scraping. KOH mount of the lesions revealed a specific organism. What is the most likely causative agent?

Accepted Answer

Malassezia furfur

Answer

Tinea rubrum

Answer

Epidermophyton floccosum

Answer

Candida albicans

Question 2

A 16-year-old patient was recently diagnosed with HIV. Which of the following fungal nail infections could be associated?

Accepted Answer

Proximal subungual onychomycosis

Answer

Distal onychomycosis

Answer

White superficial onychomycosis

Answer

Paronychia with Candida onychomycosis

Question 3

The appearance of this foot is most consistent with which one of the following diagnoses?

Accepted Answer

Chromomycosis

Answer

Buruli ulcer

Answer

Leishmaniasis

Answer

Madura foot

Question 4

A patient presents with a non-itchy plaque positive for hyphae. What is the most likely diagnosis?

Accepted Answer

Tinea incognito

Answer

Tinea capitis

Answer

Tinea corporis

Answer

Tinea facei

Question 5

A thirty-two-year-old adult male presents with a chronic suppurative lesion on the angle of the jaw. Microscopic examination shows small abscesses immediately beneath the epidermis with moderate growth of epithelial cords. In the abscess, there are oval, unicellular organisms measuring 20 µm in diameter and having a thick, double-refractive cell wall and cytoplasm containing refractive granules and vacuoles. Which of the following is the most likely diagnosis?

Accepted Answer

Blastomycosis

Answer

Foreign body reaction

Answer

Syphilis

Answer

Tuberculosis

Question 6

Dermatophytids are defined as:

Accepted Answer

Cutaneous lesions secondary to a hypersensitivity reaction to fungal antigens.

Answer

Fungal hyphae in the skin.

Answer

Vegetative fungal cells within keratinised tissue.

Answer

Dead fungal tissue.

Question 7

Which of the following tests is likely to be helpful in diagnosing a patient presenting with an itchy annular plaque on the face?

Accepted Answer

Potassium hydroxide mount

Answer

Gram's stain

Answer

Tissue smear

Answer

Wood's lamp examination

Question 8

What is the management for the given case?

Accepted Answer

Antifungals treatment for oral candidiasis

Answer

Vitamin supplements

Answer

Stop smoking and screen for carcinoma

Answer

Dapsone plus steroids

Question 9

Potassium iodide is useful in the treatment of which of the following conditions?

Accepted Answer

Sporotrichosis

Answer

Impetigo

Answer

Viral warts

Answer

Dermatitis herpetiformis

Question 10

In dermatophytosis, which antifungal drug is not indicated?

Accepted Answer

Amphotericin B

Answer

Fluconazole

Answer

Terbinafine

Answer

Griseofulvin

Fungal Skin Infections — MCQs

Fungal Skin Infections — MCQs

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