Mycology Practice Questions

Q: Pityriasis versicolor is caused by

Malassezia furfur. ***Malassezia furfur*** - **Pityriasis versicolor** is a superficial fungal infection caused by yeasts of the genus **Malassezia**, with **_Malassezia furfur_** being the most common species implicated. - This fungus normally resides on the skin but can overgrow under certain conditions (e.g., heat, humidity, oily skin), leading to characteristic **discolored patches**. *T. rubrum* - **_T. rubrum_** (Trichophyton rubrum) is a common **dermatophyte** responsible for various tinea infections, such as tinea pedis (**athlete's foot**) and tinea cruris (**jock itch**). - It causes infections in the **keratinized tissues** (skin, hair, nails) but is not the causative agent of pityriasis versicolor. *Candida species* - **_Candida_ species**, particularly **_Candida albicans_**, are yeasts that commonly cause **candidiasis** (e.g., oral thrush, vaginal yeast infections, diaper rash). - These infections typically present with **erythematous** and **pruritic** lesions, often in immunocompromised individuals or in moist body folds, which differs from pityriasis versicolor. *E. floccosum* - **_E. floccosum_** (Epidermophyton floccosum) is another **dermatophyte** primarily associated with infections of the skin and nails, causing conditions like **tinea pedis**, tinea cruris, and **onychomycosis**. - It does not cause pityriasis versicolor; this genus specifically attacks **superficial keratinized structures** and lacks the ability to invade living tissues.

Q: Which of the following is a false statement about the respective fungal infections?

Microsporium involves nail. ***Microsporium involves nail*** - This statement is considered **false** for exam purposes because *Microsporum* species are **NOT primary causes** of **tinea unguium** (onychomycosis). - *Microsporum* species primarily cause **tinea capitis** (scalp ringworm) and **tinea corporis** (body ringworm). While rare cases of nail involvement have been reported, it is clinically insignificant. - **Tinea unguium** (onychomycosis) is predominantly caused by ***Trichophyton rubrum*** and ***Trichophyton mentagrophytes***, with *Epidermophyton floccosum* and *Candida* species also playing roles. *Superficial layers of skin are involved* - This is a **true statement** because dermatophyte infections generally affect the **stratum corneum**, hair, and nails, which are all superficial keratinized tissues. - These fungi are unable to penetrate deeper viable tissue due to their inability to grow at core body temperature and the presence of inhibitory factors in serum. *Candida albicans causes skin infection* - This is a **true statement** as *Candida albicans* is a common cause of **cutaneous candidiasis**, manifesting as intertrigo, diaper rash, and paronychia. - It thrives in warm, moist environments and can infect skin folds, mucous membranes, and damaged skin. *Epidermophyton doesn't involve hair* - This is a **true statement** because *Epidermophyton floccosum* is unique among dermatophytes in that it primarily causes infections of the **skin** (tinea corporis, tinea cruris, tinea pedis) and **nails** (onychomycosis) but **does not infect hair follicles**. - Unlike *Trichophyton* and *Microsporum*, *Epidermophyton* lacks the enzymatic machinery to invade hair shafts.

Q: Thrush refers to

Acute pseudomembranous candidiasis. ***Acute pseudomembranous candidiasis*** - **Thrush** is the common term for **acute pseudomembranous candidiasis**, characterized by creamy white, cottage cheese-like plaques on the oral mucosa that can be scraped off [1]. - It is typically caused by **Candida albicans** and often seen in infants, immunocompromised individuals, or those using antibiotics or corticosteroids [1]. *Acute atrophic candidiasis* - This form presents as a **red, raw, and painful** area, often after antibiotic use, and does not have the classic white plaques associated with thrush. - It involves mucosal thinning and inflammation due to fungal overgrowth, lacking the pseudomembrane. *Chronic atrophic candidiasis* - Often associated with **denture wearers** (denture stomatitis) and appears as erythema and edema beneath the denture, without significant white lesions. - It is a persistent inflammation and redness of the mucosa due to chronic candidal infection under an ill-fitting or poorly cleaned denture. *Chronic hyperplastic candidiasis* - This is a less common form characterized by **non-scrapable white lesions** that can appear nodular or homogeneous and are often considered potentially malignant. - It involves fungal invasion into the deeper layers of the epithelium, leading to hyperkeratosis and epithelial hyperplasia, making the lesions firmly adherent.

Q: Which of the following is NOT a fungal infection?

Mycoses fungoides. ***Mycoses fungoides*** - This is a type of **cutaneous T-cell lymphoma**, which is a **malignancy of lymphocytes**, not a fungal infection [1]. - It presents with skin lesions that can mimic various dermatological conditions but is characterized by abnormal T-cells infiltrating the skin [1], [2]. *Black Piedra* - This is a superficial fungal infection of the **hair shaft** caused by **Piedraia hortae**, forming hard, black nodules. - It is an example of a **dermatomycosis**. *White Piedra* - This is a fungal infection of the **hair shaft** caused by **Trichosporon species**, leading to soft, white to light brown nodules. - Like black piedra, it is also a **dermatomycosis**. *Tinea nigra Palmaris* - This is a superficial fungal infection of the **stratum corneum** of the skin, primarily on the palms and soles, caused by **Hortaea werneckii**. - It presents as irregular, darkly pigmented (brown to black) macules and is a true **mycosis**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 613-614. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 564-565.

Q: 'Pityriasis versicolor' is caused by:

Malassezia furfur. ***Malassezia furfur*** - **Pityriasis versicolor** is a superficial fungal infection of the skin caused by the dimorphic yeast **Malassezia furfur** (also known as Pityrosporum ovale). - This organism is part of the normal skin flora but can become pathogenic under certain conditions, leading to characteristic **hypopigmented or hyperpigmented patches**, often on the trunk. *Nocardia species* - **Nocardia** are aerobic, gram-positive bacteria that typically cause **pulmonary, cutaneous, or disseminated infections**, particularly in immunocompromised individuals. - They are known for causing conditions like **nocardiosis**, which presents with abscesses, not pityriasis versicolor. *Aspergillus fumigatus* - **Aspergillus fumigatus** is a common mold that can cause a range of diseases, primarily in the respiratory tract, including **allergic bronchopulmonary aspergillosis (ABPA)**, **aspergilloma**, and **invasive aspergillosis**. - It is not associated with superficial skin infections like pityriasis versicolor. *Trichophyton rubrum* - **Trichophyton rubrum** is a dermatophyte fungus that commonly causes **tinea (ringworm) infections** of the skin, hair, and nails, such as **athlete's foot (tinea pedis)**, **jock itch (tinea cruris)**, and **nail infections (onychomycosis)**. - Unlike Malassezia, it invades the keratinized structures of the epidermis, not just superficial layers causing versicolor lesions.

Q: A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?

Blastomyces dermatitidis. ***Blastomyces dermatitidis*** - This organism is endemic to the **Ohio River valley** and is known to cause **granulomatous inflammation**, including in the prostate. - Its characteristic morphology is **broad-based budding yeast** on microscopy, fitting the description. *Escherichia coli* - While *E. coli* is a common cause of **bacterial prostatitis**, it does not present as granulomatous inflammation. - It is a **bacterium**, not a fungus, and would not show broad-based budding organisms. *Histoplasma capsulatum* - **Histoplasma** is also endemic to the Ohio River valley and causes granulomatous disease, but its yeast forms are **small**, intracellular, and do not exhibit broad-based budding. - It is often associated with a history of exposure to **bat or bird droppings** and commonly affects the lungs. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* causes **bacterial infections**, often in immunocompromised individuals or associated with catheter use, and is not a fungus. - It causes **acute inflammation**, not chronic granulomatous inflammation, and does not show broad-based budding.

Q: Medlar bodies are found in -

Chromoblastomycosis. ***Chromoblastomycosis*** - **Medlar bodies**, also known as **sclerotic bodies** or **copper pennies**, are thick-walled, septate, dematiaceous fungal cells characteristic of chromoblastomycosis. - They are typically found within **giant cells** or extracellularly in the dermis during histological examination of infected tissue. *Mycetoma* - Characterized by the presence of **grains** or **granules** composed of aggregated fungal hyphae (eumycetoma) or bacterial filaments (actinomycetoma) within the tissue [2]. - It presents as a chronic, progressive infection involving the skin, subcutaneous tissue, and often underlying bone [2]. *Histoplasmosis* - Caused by **_Histoplasma capsulatum_**, a dimorphic fungus that appears as small, oval, budding yeast cells within **macrophages** in infected tissues [1]. - It primarily affects the lungs but can disseminate to other organs, especially in immunocompromised individuals [1]. *Sporotrichosis* - Caused by **_Sporothrix schenckii_**, which appears as small, cigar-shaped budding yeast forms or asteroid bodies (yeast cells surrounded by an eosinophilic cuticle) in tissue. - It typically presents as **lymphocutaneous lesions** following traumatic inoculation of fungal spores [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 393-394.

Q: Oral candidiasis can be classified as primary and _____ based on underlying predisposing factors:

Secondary infections. ***Secondary infections*** - **Oral candidiasis** is classified as primary when it originates in the oral cavity due to localized factors. - It's classified as **secondary** when it occurs as a manifestation of a systemic disease or condition affecting the entire body, such as being **immunocompromised** [1]. *Chronic infections* - This term describes the **duration** of an infection, not its origin or underlying predisposing factors. - While oral candidiasis can become chronic, this classification does not relate to whether it's primary or secondary. *Recurrent infections* - This refers to infections that **reappear** after a period of resolution, indicating a cycle of disease [1]. - It does not categorize candidiasis based on the initial predisposing factors as primary or secondary. *Subclinical infections* - A **subclinical infection** is one that produces no noticeable symptoms, even though the pathogen is present in the body. - This classification refers to the **symptomology** of the infection, not whether it is primary or secondary in origin.

Q: The yeast which shows thick gelatinous capsule and positive for mucicarmine is

Cryptococcus neoformans. ***Cryptococcus neoformans*** - This yeast is uniquely characterized by its prominent **polysaccharide capsule**, which appears as a thick, gelatinous layer around the cell. - The capsule stains **red with mucicarmine**, a special stain used to highlight mucopolysaccharides, aiding in its identification. *Paracoccidioides brasiliensis* - This dimorphic fungus is known for its **"pilot wheel"** or **"mariner's wheel"** appearance in tissue, with multiple budding cells. - It does not possess a thick, gelatinous capsule nor does it stain positively with mucicarmine in the same distinct manner as *Cryptococcus*. *Histoplasma capsulatum* - This dimorphic fungus is typically visualized as **small, oval yeast cells** found within macrophages in tissue. - It lacks a prominent capsule and does not stain with mucicarmine. *Blastomyces dermatitidis* - This dimorphic fungus is characterized by its **large, broad-based budding yeast cells** in tissue. - It does not have a capsule and is not identified by mucicarmine staining.

Q: Which organism does not affect hair?

Epidermophyton floccosum. ***Epidermophyton floccosum*** - This fungus primarily affects the **skin and nails**, causing conditions like **tinea cruris** (jock itch) and **tinea pedis** (athlete's foot). - Unlike *Trichophyton* and *Microsporum*, *Epidermophyton floccosum* does not have the enzymatic machinery to invade or colonize hair shafts. *Trichophyton rubrum* - This organism is a common cause of **dermatophytosis**, and it frequently infects hair, particularly in conditions like **tinea capitis** (scalp ringworm) and **tinea barbae**. - It can invade the hair shaft both **endothrix** (inside the hair) and **ectothrix** (outside the hair) depending on the species and type of infection. *Microsporum* - *Microsporum* species are well-known for causing infections of the hair and are a major cause of **tinea capitis**, especially in children. - The infection typically presents as an **ectothrix** pattern, where fungal spores are found on the outside of the hair shaft. *All of the options* - This option is incorrect because both *Trichophyton rubrum* and *Microsporum* species are known to infect hair. - Only *Epidermophyton floccosum* does not typically affect hair.

Question 1

Pityriasis versicolor is caused by

Accepted Answer

Malassezia furfur

Answer

T. rubrum

Answer

Candida species

Answer

E. floccosum

Question 2

Which of the following is a false statement about the respective fungal infections?

Accepted Answer

Microsporium involves nail

Answer

Superficial layers of skin are involved

Answer

Candida albicans causes skin infection

Answer

Epidermophyton doesn't involve hair

Question 3

Thrush refers to

Accepted Answer

Acute pseudomembranous candidiasis

Answer

Acute atrophic candidiasis

Answer

Chronic atrophic candidiasis

Answer

Chronic hyperplastic candidiasis

Question 4

Which of the following is NOT a fungal infection?

Accepted Answer

Mycoses fungoides

Answer

Black Piedra

Answer

White Piedra

Answer

Tinea nigra Palmaris

Question 5

'Pityriasis versicolor' is caused by:

Accepted Answer

Malassezia furfur

Answer

Nocardia species

Answer

Aspergillus fumigatus

Answer

Trichophyton rubrum

Question 6

A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?

Accepted Answer

Blastomyces dermatitidis

Answer

Escherichia coli

Answer

Histoplasma capsulatum

Answer

Pseudomonas aeruginosa

Question 7

Medlar bodies are found in -

Accepted Answer

Chromoblastomycosis

Answer

Mycetoma

Answer

Histoplasmosis

Answer

Sporotrichosis

Question 8

Oral candidiasis can be classified as primary and _____ based on underlying predisposing factors:

Accepted Answer

Secondary infections

Answer

Chronic infections

Answer

Recurrent infections

Answer

Subclinical infections

Question 9

The yeast which shows thick gelatinous capsule and positive for mucicarmine is

Accepted Answer

Cryptococcus neoformans

Answer

Paracoccidioides brasiliensis

Answer

Histoplasma capsulatum

Answer

Blastomyces dermatitidis

Question 10

Which organism does not affect hair?

Accepted Answer

Epidermophyton floccosum

Answer

Trichophyton rubrum

Answer

Microsporum

Answer

All of the options

Mycology — MCQs

Mycology — MCQs

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