Dermatophytes — MCQs
A child presents with multiple patchy areas of hair loss, scales, and itching. The sister also had similar lesions. What is the most likely diagnosis?
A 7 year old boy with boggy swelling of the scalp with multiple discharging sinuses with cervical lymphadenopathy with easily pluckable hair. What would be done for diagnosis?
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 fungal culture shows 'rising sun' pattern. Which microscopic finding would confirm Microsporum canis?
Tinea "incognito" is due to inappropriate use of systemic and topical:
Dermatophytes affect -
A hair perforation test was performed on a yeast isolate, and the result was positive. Which of the following organisms is associated with a positive hair perforation test?
Which organism is incriminated in causing the following lesions? (Recent NEET Pattern 2016-17)
All are true about the bacteria shown in the figure except: (Recent NEET Pattern 2016-17)
Dermatophytes Indian Medical PG Practice Questions and MCQs
Question 1: A child presents with multiple patchy areas of hair loss, scales, and itching. The sister also had similar lesions. What is the most likely diagnosis?
- A. Alopecia areata
- B. Tinea capitis (Correct Answer)
- C. Pediculosis capitis
- D. Pyoderma
Explanation: ***Tinea capitis*** - **Tinea capitis** presents with **patchy hair loss**, **scaling**, and **itching** on the scalp, which are classic signs of a fungal infection. - The fact that the sister also had similar lesions indicates a **contagious** condition, consistent with a **dermatophyte infection**. *Alopecia areata* - Characterized by **sudden, non-scarring hair loss** in circular or oval patches, often with no scaling or inflammation. - It is an **autoimmune condition** and typically not associated with itching or contagiousness amongst siblings. *Pediculosis capitis* - This condition involves an **infestation of head lice**, primarily causing **intense itching** of the scalp. - While it is contagious, it typically presents with **nits** (lice eggs) firmly attached to hair shafts and excoriations from scratching, rather than significant hair loss and scaling. *Pyoderma* - **Pyoderma** is a bacterial skin infection, often presenting as **pustules**, **crusts**, or **blisters** on the scalp. - While it can be contagious and cause discomfort, it is primarily characterized by purulent lesions and not the diffuse patchy hair loss and scaling seen in this case.
Question 2: A 7 year old boy with boggy swelling of the scalp with multiple discharging sinuses with cervical lymphadenopathy with easily pluckable hair. What would be done for diagnosis?
- A. Pus for culture
- B. Biopsy
- C. KOH mount (Correct Answer)
- D. None of the options
Explanation: ***KOH mount*** - A **KOH mount** (potassium hydroxide wet mount) is the most appropriate **initial rapid diagnostic test** for suspected **tinea capitis** with **kerion formation**, allowing immediate visualization of fungal elements (hyphae and spores). - The clinical presentation of boggy scalp swelling, discharging sinuses, cervical lymphadenopathy, and easily pluckable hair is classic for **kerion**, a severe inflammatory form of tinea capitis caused by dermatophytes (commonly *Trichophyton* or *Microsporum* species). - KOH mount is **quick, inexpensive, and readily available**, making it ideal for immediate diagnosis in clinical practice, though fungal culture may be performed subsequently for species identification. *Pus for culture (bacterial)* - While bacterial culture might be performed to rule out **secondary bacterial infection**, it does not diagnose the underlying **fungal etiology** of kerion. - The primary pathogen in kerion is a dermatophyte fungus, not bacteria, though secondary bacterial infection can occur. *Biopsy* - A **biopsy** is usually reserved for cases that are atypical, treatment-resistant, or when there is diagnostic uncertainty with other conditions (e.g., dissecting cellulitis, bacterial abscess). - It is an **invasive procedure** and not the first-line diagnostic approach for a clinically obvious case of kerion. *None of the options* - Given the classic clinical presentation of kerion, a definitive diagnostic method (KOH mount) is required to confirm the fungal infection and guide appropriate systemic antifungal treatment. - Therefore, choosing "None of the options" would be incorrect.
Question 3: 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 4: 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 5: A fungal culture shows 'rising sun' pattern. Which microscopic finding would confirm Microsporum canis?
- A. Spiral hyphae
- B. Banana-shaped macroconidia (Correct Answer)
- C. Racquet hyphae
- D. Chlamydospores
Explanation: ***Banana-shaped macroconidia*** - The 'rising sun' colonial pattern on fungal culture is characteristic of *Microsporum canis*, and the key microscopic feature confirming this diagnosis is the presence of **spindle-shaped** or **banana-shaped macroconidia** with rough, thick walls. - These macroconidia typically have 6-15 cells and are observed upon microscopic examination of the fungal culture. *Spiral hyphae* - **Spiral hyphae** are a characteristic microscopic feature seen in *Trichophyton mentagrophytes*, not typically in *Microsporum canis*. - They are coiled or corkscrew-like hyphal structures. *Racquet hyphae* - **Racquet hyphae** are microscopic structures with a swollen, club-shaped end resembling a tennis racquet, often found in various dermatophytes but not specifically diagnostic for *Microsporum canis*. - They are considered a less specific morphological feature. *Chlamydospores* - **Chlamydospores** are thick-walled, asexual spores that are resistant to adverse conditions and are commonly seen in other fungi, such as *Candida albicans* (especially terminal chlamydospores), but not a distinguishing feature for *Microsporum canis*. - They are a survival form of the fungus.
Question 6: Tinea "incognito" is due to inappropriate use of systemic and topical:
- A. Steroids (Correct Answer)
- B. Antibiotics
- C. Antivirals
- D. Antifungals
Explanation: ***Steroids*** - The use of **topical or systemic steroids** can mask the typical presentation of tinea infections, leading to a modified appearance known as tinea "incognito." - Steroids reduce inflammation and symptoms like itching and redness, but they do not eliminate the fungal infection, often allowing it to spread or become more extensive. *Antibiotics* - Antibiotics are used to treat **bacterial infections** and have no direct effect on fungal organisms that cause tinea. - While inappropriate use of antibiotics can lead to other issues, it does not cause the characteristic presentation of tinea incognito. *Antivirals* - Antivirals are specifically used for **viral infections** and are ineffective against fungal pathogens. - Their use would not lead to the altered clinical presentation of a tinea infection. *Antifungals* - Antifungals are the direct treatment for tinea infections; however, their **inappropriate or insufficient use** might lead to treatment failure or resistance, but not the "incognito" appearance. - Tinea incognito specifically arises when inflammatory agents like steroids suppress visible signs without eradicating the fungus.
Question 7: Dermatophytes affect -
- A. Dermis of skin
- B. Keratin (Correct Answer)
- C. Stratum spongiosum
- D. Stratum basale
Explanation: ***Keratin*** - **Dermatophytes** are a group of fungi that have a unique ability to digest **keratin**, a protein found in **skin, hair, and nails**. - This characteristic allows them to colonize and thrive in these superficial tissues, causing infections like **tinea corporis** (ringworm) or **tinea pedis** (athlete's foot). *Dermis of skin* - The **dermis** is the layer of skin beneath the epidermis, rich in **collagen, elastin, blood vessels, and nerves**. - Dermatophytes do not typically invade the dermis; their infections are generally limited to the **stratum corneum** and other keratinized structures. *Stratum spongiosum* - **Stratum spongiosum** is a term sometimes used to describe an edematous (swollen) epidermis, often seen in **eczema** and **dermatitis**. - Dermatophytes do not target this specific architectural change in the epidermis but rather feed on the keratin present in the more superficial layers. *Stratum basal* - The **stratum basale** (also called stratum germinativum) is the deepest layer of the **epidermis**, responsible for cell division and producing new skin cells. - Dermatophytes primarily infect the **dead keratinized cells** of the stratum corneum rather than the metabolically active cells of the stratum basale.
Question 8: A hair perforation test was performed on a yeast isolate, and the result was positive. Which of the following organisms is associated with a positive hair perforation test?
- A. Candida tropicalis
- B. Candida glabrata
- C. Candida parapsilosis
- D. Candida albicans (Correct Answer)
Explanation: ***Candida albicans*** - The **hair perforation test** is a classic diagnostic test specifically used to identify *Candida albicans*, which characteristically produces **conical projections** when incubated with sterilized blonde hair in water at room temperature. - This test has historically been used as a simple, rapid method for **presumptive identification** of *C. albicans* from other Candida species, indicating the organism's ability to produce **keratinolytic enzymes**. *Candida tropicalis* - *Candida tropicalis* gives a **negative hair perforation test** and does not produce the characteristic hair perforations seen with *C. albicans*. - While it can form **pseudohyphae** and true hyphae, it can be differentiated from *C. albicans* using this test among others. *Candida glabrata* - *Candida glabrata* does **NOT** produce a positive hair perforation test and typically remains in **yeast form**. - It is distinguished from other Candida species by its **smaller cell size** and inability to form germ tubes or hair perforations. *Candida parapsilosis* - *Candida parapsilosis* also gives a **negative hair perforation test** and does not produce hair perforations. - This species can form **pseudohyphae** but the hair perforation test helps distinguish it from *C. albicans*.
Question 9: Which organism is incriminated in causing the following lesions? (Recent NEET Pattern 2016-17)
- A. Streptococcus pyogenes (Correct Answer)
- B. Streptococcus pneumoniae
- C. Enterococcus
- D. Staphylococcus aureus
Explanation: ***Streptococcus pyogenes*** - The image depicts **impetigo**, characterized by crusted lesions, often found on the face. - **Streptococcus pyogenes** (Group A Streptococcus) is a common cause of impetigo, either alone or in combination with *Staphylococcus aureus*. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is primarily associated with **respiratory tract infections**, such as pneumonia and otitis media, not skin lesions like impetigo. - While it can cause invasive diseases, its primary presentation is typically not superficial skin infections. *Enterococcus* - *Enterococcus* species are common inhabitants of the normal **gastrointestinal flora** and are frequently implicated in **urinary tract infections**, endocarditis, and hospital-acquired infections. - They are generally not a primary cause of impetigo or similar superficial skin infections. *Staphylococcus aureus* - While *Staphylococcus aureus* is a very common cause of **impetigo**, the question asks for "the organism" as if there is only one most specific answer without providing other context, suggesting **Streptococcus pyogenes** as a highly relevant primary pathogen, especially if non-bullous impetigo is implied by the crusted appearance. - *S. aureus* often presents with **purulent lesions** (e.g., boils, carbuncles) and bullous impetigo with fluid-filled blisters which eventually rupture and crust.
Question 10: All are true about the bacteria shown in the figure except: (Recent NEET Pattern 2016-17)
- A. Commensal in upper respiratory tract of humans
- B. Kovac's method results in formation of deep purple color
- C. Nonhemolytic, gray translucent colonies
- D. Resistant to heat, alteration in pH and disinfectants (Correct Answer)
Explanation: ***Resistant to heat, alteration in pH and disinfectants*** - The bacteria shown in the figure are **Gram-negative diplococci**, characteristic of **Neisseria gonorrhoeae** or **Neisseria meningitidis**. These bacteria are known to be **sensitive to drying, heat, cold, and disinfectants**, not resistant. - Their delicate nature makes them difficult to cultivate outside specific laboratory conditions and contributes to their typical mode of transmission through close contact. *Commensal in the upper respiratory tract of humans* - **Neisseria meningitidis**, a type of diplococci shown and inferred, is a common **commensal** in the nasopharynx of up to 10% of the population. - This colonization can be entirely asymptomatic, but it also serves as a reservoir for potential invasive disease. *Kovac's method results in the formation of a deep purple color* - **Neisseria** species are **oxidase-positive**, meaning they produce cytochrome c oxidase. - The **Kovac's oxidase test** uses N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride, which, in the presence of cytochrome c oxidase, gets oxidized to a **deep purple color**. *Nonhemolytic, gray translucent colonies* - Both *Neisseria gonorrhoeae* and *Neisseria meningitidis* typically form **nonhemolytic** colonies on blood agar. - The colonies are often described as **grayish-white or translucent** with smooth edges, especially after 24-48 hours of incubation.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free