Dermatophytoses — MCQs
A 10-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hair, and lymph nodes enlarged in occipital region, which of the following would be most helpful for diagnostic evaluation?
Which of the following conditions is NOT caused by Aspergillus?
An eleven-year-old boy has Tinea capitis on his scalp. Which of the following is the most appropriate line of treatment for this condition?
A patient presents with annular, scaly plaques with perifollicular extension on the trunk. What is the most likely diagnosis?
Which of the following is not a part of P. versicolor treatment -
A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?
A 30-year-old washerwoman presents with the following lesion. All are correct except:
Skin scraping and KOH mounting is done for what condition?
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?
What is the most likely diagnostic test to help diagnose a patient presenting with an itchy annular plaque on the face?
Dermatophytoses Indian Medical PG Practice Questions and MCQs
Question 1: A 10-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hair, and lymph nodes enlarged in occipital region, which of the following would be most helpful for diagnostic evaluation?
- A. Bacterial culture
- B. Biopsy and giemsa staining
- C. Patch test, gram staining and Tzank smear
- D. KOH mount (Correct Answer)
Explanation: ***KOH mount*** - The symptoms of **painful boggy scalp swelling**, **purulent discharge**, **easily pluckable hair**, and **occipital lymphadenopathy** in a child are highly suggestive of **Tinea capitis**, specifically **Kerion**. - A **KOH mount** is the most direct and rapid method to identify fungal elements (hyphae and spores) in hair shafts and scales, confirming the diagnosis of a dermatophyte infection. *Bacterial culture* - While there is **purulent discharge**, the primary presentation with **boggy swelling** and **hair loss** is more indicative of a fungal etiology. - A bacterial culture would only be useful to rule out secondary bacterial infection, but not as the initial diagnostic step for the described primary fungal condition. *Biopsy and Giemsa staining* - A **biopsy** is an invasive procedure and generally not the first-line diagnostic test for uncomplicated **Tinea capitis/Kerion**, where a non-invasive KOH mount is sufficient. - **Giemsa staining** is primarily used for identifying certain bacteria, parasites, or cellular morphology, but it is not the standard or most efficient method for diagnosing fungal infections of the hair. *Patch test, Gram staining and Tzank smear* - A **patch test** is used to diagnose **allergic contact dermatitis** and is irrelevant to the presented symptoms. - **Gram staining** is for bacterial identification, and a **Tzank smear** is used for viral infections like herpes, neither of which are indicated by the clinical picture of a fungal scalp infection.
Question 2: Which of the following conditions is NOT caused by Aspergillus?
- A. Otomycosis
- B. Dermatophytosis (Correct Answer)
- C. Allergic sinusitis
- D. Bronchopulmonary allergy
Explanation: ***Dermatophytosis*** - This condition is caused by **dermatophytes** (e.g., *Trichophyton*, *Microsporum*, *Epidermophyton*), which are a specific group of fungi that metabolize keratin. - *Aspergillus* species are generally **opportunistic molds** but do not typically cause dermatophytosis, which is a superficial fungal infection of the skin, hair, or nails. *Otomycosis* - **Otomycosis** is a fungal infection of the external ear canal, and *Aspergillus* species are a common cause, particularly *Aspergillus niger*. - It can lead to ear pain, discharge, itching, and hearing impairment. *Allergic sinusitis* - **Allergic fungal sinusitis (AFS)** is a common form of fungal sinusitis where *Aspergillus* species are significant contributors, often leading to a thick, tenacious allergic mucin. - This condition is an IgE-mediated hypersensitivity reaction to the fungal elements in the nasal and sinus cavities. *Bronchopulmonary allergy* - **Allergic bronchopulmonary aspergillosis (ABPA)** is a hypersensitivity reaction to *Aspergillus fumigatus* antigens that colonize the airways, particularly in individuals with asthma or cystic fibrosis. - It results in recurrent episodes of wheezing, cough, and transient pulmonary infiltrates, and can lead to bronchiectasis if left untreated.
Question 3: An eleven-year-old boy has Tinea capitis on his scalp. Which of the following is the most appropriate line of treatment for this condition?
- A. Shaving of the scalp
- B. Topical griseofulvin therapy
- C. Oral griseofulvin therapy (Correct Answer)
- D. Selenium sulphide shampoo
Explanation: ***Oral griseofulvin therapy*** - **Systemic antifungal agents** are essential for treating **Tinea capitis**, as the fungal infection is deep within the hair follicles and cannot be reached effectively by topical treatments alone. - **Griseofulvin** is a well-established and effective oral antifungal for **Tinea capitis** in children. *Shaving of the scalp* - While shaving the scalp might reduce some fungal load and facilitate topical treatment, it is **not a definitive treatment** for **Tinea capitis** on its own, as the infection remains deep in the hair follicles. - It does not address the underlying systemic nature of the infection within the hair shaft. *Topical griseofulvin therapy* - **Topical griseofulvin** is generally **ineffective** for **Tinea capitis** because the fungus resides deep within the hair follicle and hair shaft, where topical preparations cannot penetrate sufficiently. - **Systemic absorption** is required to deliver adequate drug concentrations to the site of infection. *Selenium sulphide shampoo* - **Selenium sulfide shampoo** can be used as an **adjunctive therapy** to reduce shedding of spores and prevent spread, but it is **not curative** for **Tinea capitis**. - It helps to reduce skin scaling and fungal burden on the surface but does not eradicate the infection deep within the hair follicles.
Question 4: A patient presents with annular, scaly plaques with perifollicular extension on the trunk. What is the most likely diagnosis?
- A. Psoriasis
- B. Lichen planus
- C. Tinea (Correct Answer)
- D. Pityriasis versicolor
Explanation: ***Tinea*** - **Tinea corporis** classically presents with **annular, scaly plaques with central clearing** and an active, raised border. - On hairy areas or with follicular involvement, dermatophyte infections show **perifollicular extension** as the fungus invades hair follicles. - The **annular morphology with scale** is pathognomonic for dermatophyte infection, confirmed by **KOH preparation** showing septate hyphae. - Common sites include trunk, limbs, and any body area with hair follicles. *Psoriasis* - Presents with **well-demarcated, erythematous plaques** with **silvery-white scales**, typically on extensor surfaces (elbows, knees, scalp). - **Follicular psoriasis** is rare and shows **pinpoint follicular papules**, not annular plaques with perifollicular extension. - Auspitz sign (pinpoint bleeding on scale removal) helps differentiate from tinea. *Lichen planus* - Characterized by **pruritic, polygonal, purple, planar papules** (the "6 Ps"). - **Lichen planopilaris** (follicular variant) causes **scarring alopecia** with follicular hyperkeratosis, not annular scaly plaques. - Wickham striae may be visible on mucosal surfaces. *Pityriasis versicolor* - Caused by **Malassezia species**, presents as **hypo- or hyperpigmented macules** with fine scale on trunk and upper arms. - **Follicular variant** (pityriasis folliculorum) shows discrete follicular papules, NOT annular plaques. - "Spaghetti and meatballs" appearance on KOH prep (short hyphae and spores) differentiates from dermatophytes.
Question 5: Which of the following is not a part of P. versicolor treatment -
- A. Selenium sulfide
- B. Clotrimazole
- C. Ketoconazole
- D. Griseofulvin (Correct Answer)
Explanation: **Griseofulvin (Correct - NOT used for P. versicolor)** - **Griseofulvin** interferes with fungal cell division and is primarily used for dermatophyte infections of the skin, hair, and nails, not superficial yeast infections like *P. versicolor*. - It is systemically absorbed and incorporated into **keratin precursor cells**, offering protection against dermatophytes in newly formed tissue. - *Malassezia* species (causing P. versicolor) are **yeasts**, not dermatophytes, making griseofulvin ineffective. *Selenium sulfide (Incorrect - IS used)* - **Selenium sulfide** is an effective topical antifungal agent commonly used in shampoos and lotions to treat *P. versicolor* by inhibiting the growth of *Malassezia* species. - It works by reducing **sebum production** and having a direct fungistatic effect on the yeast. *Clotrimazole (Incorrect - IS used)* - **Clotrimazole** is a broad-spectrum azole antifungal that is very effective as a topical treatment for *P. versicolor* by inhibiting ergosterol synthesis in the fungal cell membrane. - It works well for localized patches of the infection. *Ketoconazole (Incorrect - IS used)* - **Ketoconazole**, another azole antifungal, is highly effective for *P. versicolor* and can be used topically (shampoos, creams) or orally in more extensive or recalcitrant cases. - It disrupts the fungal cell membrane by inhibiting the synthesis of **ergosterol**.
Question 6: A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?
- A. Tzanck smear
- B. KOH mount (Correct Answer)
- C. Woods lamp
- D. Biopsy
Explanation: ***KOH mount*** - A **KOH mount** (potassium hydroxide) dissolves keratinocytes, allowing for direct visualization of fungal elements such as **hyphae** and **spores** under a microscope. This is the **most rapid and cost-effective test** for confirming fungal infections like **onychomycosis**. - The patient's presentation with **yellowish discoloration** and **"tunneling"** of nails (suggesting onycholysis and subungual hyperkeratosis), along with a history of recurrent groin itching (potentially **tinea cruris**), strongly points to a fungal infection. *Tzanck smear* - A **Tzanck smear** is primarily used to detect multinucleated giant cells in **herpesvirus infections** (e.g., herpes simplex, varicella-zoster). - It is not useful for identifying fungal elements responsible for nail discoloration or suspected onychomycosis. *Woods lamp* - A **Woods lamp** uses ultraviolet light to detect specific fluorescent substances, particularly useful for diagnosing certain **bacterial infections** (e.g., *Corynebacterium minutissimum* in erythrasma) or some **tinea capitis** species (*Microsporum*). - Most common dermatophytes causing onychomycosis **do not fluoresce** under a Wood's lamp, making it an unreliable diagnostic tool in this scenario. *Biopsy* - A **nail biopsy** (with histology and special stains like PAS) is a highly accurate diagnostic method for onychomycosis, especially when other tests are inconclusive. - However, it is an **invasive procedure**, takes more time for results, and is generally not the **most rapid** initial test compared to a KOH mount.
Question 7: A 30-year-old washerwoman presents with the following lesion. All are correct except:
- A. Rule out diabetes mellitus in recurrent episodes
- B. Deformed nail plate
- C. Tinea unguium (Correct Answer)
- D. Caused by normal commensal of GIT
Explanation: ***Tinea unguium*** - **Tinea unguium** (onychomycosis) is a **dermatophyte infection** of the nail plate, typically caused by *Trichophyton* species, not *Candida*. - The image shows **chronic paronychia** caused by *Candida* affecting the nail fold, which is a completely different condition from tinea unguium. *Caused by normal commensal of GIT* - *Candida albicans* is indeed a **normal commensal** of the gastrointestinal tract and can cause chronic paronychia in washerwomen. - Constant **water exposure** allows this opportunistic organism to colonize and infect the periungual tissues. *Rule out diabetes mellitus in recurrent episodes* - **Recurrent candidal infections** warrant screening for **diabetes mellitus** due to impaired immune function and elevated glucose levels. - Diabetic patients have increased susceptibility to **opportunistic fungal infections** including chronic paronychia. *Deformed nail plate* - The image clearly shows **nail dystrophy** with irregular, discolored, and thickened nail plate secondary to chronic inflammation. - **Chronic paronychia** affects the nail matrix, leading to **abnormal nail growth** and permanent deformation.
Question 8: Skin scraping and KOH mounting is done for what condition?
- A. Leprosy
- B. Varicella
- C. Fungal infections (Correct Answer)
- D. Herpes Simplex Virus (HSV)
Explanation: **Explanation:** **1. Why Fungal Infections is Correct:** Potassium Hydroxide (KOH) mounting is the **gold standard bedside diagnostic test** for superficial fungal infections (Dermatophytosis, Candidiasis, and Tinea versicolor). The medical principle relies on the fact that KOH is a strong alkali that digests keratin, epithelial cells, and debris in skin scrapings, hair, or nails. Since fungal cell walls contain **chitin**, they remain resistant to KOH. This allows the clinician to clearly visualize fungal elements like hyphae, spores, or budding yeast under a microscope. **2. Why Other Options are Incorrect:** * **Leprosy (A):** Diagnosis is primarily clinical, supported by **Slit Skin Smear (SSS)** using Modified Ziehl-Neelsen staining to identify *Mycobacterium leprae* (acid-fast bacilli). * **Varicella (B) & HSV (D):** These are viral infections. The classic bedside test for these is the **Tzanck Smear**, where a scraping from the base of a vesicle is stained (Giemsa/Wright) to look for **multinucleated giant cells** (Acantholytic cells). **3. High-Yield Clinical Pearls for NEET-PG:** * **Concentration:** 10% KOH is used for skin/hair; 20% KOH is used for thicker nail clippings. * **Classic Morphologies:** * **Dermatophytes:** Translucent, branching, septate hyphae. * **Tinea Versicolor:** "Spaghetti and meatballs" appearance (short hyphae and spores). * **Candidiasis:** Pseudohyphae and budding yeast cells. * **Modification:** **DMSO (Dimethyl sulfoxide)** can be added to KOH to speed up the clearing of keratin without requiring heat.
Question 9: 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?
- A. Aspergillus
- B. Candida
- C. Mucor
- D. Trichophyton (Correct Answer)
Explanation: ### Explanation The clinical presentation described—discolored, crumbling, friable nails with distal-lateral separation (onycholysis) and subungual hyperkeratosis—is a classic description of **Distal Lateral Subungual Onychomycosis (DLSO)**. This is the most common form of onychomycosis. **1. Why Trichophyton is Correct:** Dermatophytes are responsible for approximately 90% of toenail onychomycosis. **_Trichophyton rubrum_** is the most common causative agent worldwide, followed by _Trichophyton mentagrophytes_. These fungi possess keratinases that allow them to invade and digest the keratin of the nail plate and bed. **2. Why Other Options are Incorrect:** * **Candida:** While *Candida albicans* can cause onychomycosis, it typically presents as **Chronic Mucocutaneous Candidiasis** or involves the fingernails (often associated with paronychia). It is less common in isolated toenail infections unless the patient is immunocompromised. * **Aspergillus:** This is a non-dermatophyte mold (NDM). While NDMs can cause nail infections, they are much less common than dermatophytes and usually occur secondary to trauma or underlying nail disease. * **Mucor:** This is an opportunistic fungus causing zygomycosis (mucormycosis), typically presenting as rhino-cerebral or pulmonary infections in diabetic or immunocompromised patients. It does not typically cause chronic, localized nail dystrophy. **3. NEET-PG High-Yield Pearls:** * **Most common type of Onychomycosis:** Distal Lateral Subungual Onychomycosis (DLSO). * **White Superficial Onychomycosis (WSO):** Characterized by "powdery" white patches on the nail surface; most commonly caused by _T. mentagrophytes_. * **Proximal Subungual Onychomycosis (PSO):** Often a clinical marker for **HIV/AIDS**. * **Gold Standard Diagnosis:** KOH mount (initial) and Fungal Culture (Sabouraud Dextrose Agar). * **Treatment of Choice:** Oral **Terbinafine** (Drug of choice for dermatophyte onychomycosis).
Question 10: What is the most likely diagnostic test to help diagnose a patient presenting with an itchy annular plaque on the face?
- A. Gram's stain
- B. Potassium hydroxide mount (Correct Answer)
- C. Tissue smear
- D. Wood's lamp examination
Explanation: ### Explanation **Correct Answer: B. Potassium hydroxide (KOH) mount** The clinical presentation of an **itchy annular plaque** (ring-shaped lesion with central clearing and an active, scaly border) is the classic description of **Tinea faciei**, a dermatophytosis. The gold standard bedside diagnostic test for any suspected superficial fungal infection (Dermatophytosis, Candidiasis, or Pityriasis versicolor) is the **KOH mount**. **Mechanism:** KOH acts as a keratolytic agent that dissolves keratin and cellular debris, allowing the clinician to clearly visualize fungal elements under a microscope. In dermatophytosis, one typically observes **translucent, branching, septate hyphae**. **Why other options are incorrect:** * **A. Gram’s stain:** Primarily used to identify bacterial infections (Gram-positive vs. Gram-negative). It is not the standard for diagnosing dermatophytes. * **C. Tissue smear:** (e.g., Tzanck smear) is used for diagnosing viral infections like Herpes Simplex or Varicella-Zoster (looking for multinucleated giant cells), not fungal infections. * **D. Wood’s lamp examination:** While useful for *Tinea capitis* (Microsporum species fluoresce blue-green) or Erythrasma (coral-red fluorescence), it is often negative in *Tinea corporis* and *Tinea faciei*, making KOH a more reliable and definitive diagnostic tool. **Clinical Pearls for NEET-PG:** * **Specimen Collection:** Always scrape from the **active leading edge** of the lesion, as this is where the fungal load is highest. * **KOH Concentration:** 10% KOH is used for skin/hair; 20% is used for thickened nails (Onychomycosis). * **Classic Sign:** The "Spaghetti and Meatballs" appearance on KOH is pathognomonic for **Pityriasis versicolor** (Malassezia furfur). * **Culture:** If KOH is inconclusive, **Sabouraud’s Dextrose Agar (SDA)** is the most common fungal culture medium used.
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