Fungal Diseases in Dermatology
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Questions and Answers

What is the primary causative agent of Tinea capitis in children in the US?

  • Microsporum gypseum
  • Trichophyton violaceum
  • Trichophyton tonsurans (correct)
  • Trichophyton metagrophytes

    • Which dermatophyte species is primarily associated with athlete's foot?

  • Trichophyton metagrophytes (correct)
  • Trichophyton violaceum
  • Trichophyton tonsurans
  • Microsporum gypseum

    • What feature identifies Trichophyton tonsurans when cultured on SDA medium?

  • Fluffy white colonies with extensive microconidia
  • Yellow-white granular colonies
  • Rust colored pigment on colony’s reverse (correct)
  • Green colonies with black centers

    • Which feature is typical of the macroconidia produced by Microsporum gypseum?

    <p>Thin-walled and smooth</p> Signup and view all the answers

    What is the shape of the microconidia found in Trichophyton metagrophytes?

    <p>Primarily globose, may appear tear-shaped</p> Signup and view all the answers

    Which type of hair does Trichophyton tonsurans infect?

    <p>Endothrix hair</p> Signup and view all the answers

    What is a common feature of the conidia from the genus Trichophyton?

    <p>Moderate thick-walled fusiform shapes</p> Signup and view all the answers

    What best characterizes a spiral hyphae in fungal cultures?

    <p>Twisted, corkscrew shapes</p> Signup and view all the answers

    Which of the following fungi is associated with yellow or pale brown aggregations around the hair shaft?

    <p>Trichosporon asahii</p> Signup and view all the answers

    What is the appearance of Microsporum spp. under microscopic examination?

    <p>Balloon shape appearance with distorted macroconidia</p> Signup and view all the answers

    Which organism does not grow on rice agar but rather shows malted, velvety colonies on non-fortified rice?

    <p>Microsporum audouinii</p> Signup and view all the answers

    What characteristic is notable about the macroconidia of Microsporum spp.?

    <p>Large, rough-walled, and multicellular</p> Signup and view all the answers

    Which of the following fungi is known to cause a severe and frequently fatal disease, especially in immunocompromised patients?

    <p>Trichosporon asahii</p> Signup and view all the answers

    What is the main characteristic feature of T. rubrum colonies as observed macroscopically?

    <p>Colony surfaces are cottony and white, later becoming velvety</p> Signup and view all the answers

    Which dermatophyte is known to produce 3-8 cells cylindric macroconidia?

    <p>Trichophyton rubrum</p> Signup and view all the answers

    Which test is used to differentiate T. mentagrophytes from T. rubrum?

    <p>5-day urease test</p> Signup and view all the answers

    What is the result of the urease test for T. rubrum?

    <p>Negative or requires more than 5 days</p> Signup and view all the answers

    What kind of lesions are associated with T. rubrum infections?

    <p>Clear center with red margin</p> Signup and view all the answers

    Which dermatophyte is known to cause only surface erosion of hair shafts?

    <p>Trichophyton rubrum</p> Signup and view all the answers

    What is the outcome of the Wood's lamp test for T. rubrum?

    <p>Does not glow</p> Signup and view all the answers

    What is a defining microscopic characteristic of T. mentagrophytes?

    <p>Forms perpendicular penetration pegs in hair shafts</p> Signup and view all the answers

    What method is used for confirming the diagnosis of dermatomycoses?

    <p>Direct KOH with a 10-20% solution</p> Signup and view all the answers

    Which of the following dermatophyte genera is primarily associated with infections of skin, hair, and nails?

    <p>Trichophyton</p> Signup and view all the answers

    Which characteristic is associated with Black Piedra?

    <p>Hard, dark brown to black gritty nodules</p> Signup and view all the answers

    What is the primary component of the nodules found in Black Piedra?

    <p>Ascospore chains</p> Signup and view all the answers

    What type of fungal infection does ringworm specifically cause?

    <p>Inflammation at the advancing margin of the lesion</p> Signup and view all the answers

    Which of the following fungi is classified as zoophilic?

    <p>Microsporum canis</p> Signup and view all the answers

    What type of tissues do dermatophytes primarily infect?

    <p>Keratinized tissues</p> Signup and view all the answers

    In the diagnosis of dermatophyte infections, what role does calcofluor white staining play?

    <p>It helps visualize the presence of hyphae</p> Signup and view all the answers

    What is the most common form of onychomycosis?

    <p>Subungual onychomycosis</p> Signup and view all the answers

    Which of the following is a causative agent of tinea capitis?

    <p>Trichophyton mentagrophytes</p> Signup and view all the answers

    What distinguishes gray patch ringworm from black dot ringworm?

    <p>It primarily affects the scalp.</p> Signup and view all the answers

    Which statement about tinea pedis is correct?

    <p>It arises from infected skin scales on the feet.</p> Signup and view all the answers

    What is a common characteristic of nails affected by onychomycosis?

    <p>They become thick, discolored, and flaky.</p> Signup and view all the answers

    Which form of tinea capitis is associated with brittle hair shafts that break off?

    <p>Ectothrix hair infection</p> Signup and view all the answers

    Which of the following is the least likely to be a common agent for onychomycosis?

    <p>Microsporum audouinii</p> Signup and view all the answers

    Which population is most likely to develop tinea pedis?

    <p>Athletes and those who wear shoes frequently</p> Signup and view all the answers

    Study Notes

    Diagnosis Methods for Cutaneous Mycoses

    • Direct KOH (10-20%) is a digesting agent for identifying fungi.
    • Calcofluor white staining aids in fungal visualization.
    • LPCB is used for fungal morphologic identification.
    • Woods Lamp fluorescence indicates Malassezia presence in a yellow hue.

    Dermatomycoses

    • Fungal diseases affecting keratinized tissues, including skin structures.
    • Dermatophytes, causative agents of ringworm, include three main genera:
      • Trichophyton: infects skin, hair, and nails.
      • Microsporum: primarily targets skin and hair.
      • Epidermophyton: associated with skin and nails.
    • Dermatophyte infections are restricted to nonviable skin.

    Piedra (Hair Shaft Infection)

    • "Piedra" derives from Latin, meaning “hair shaft.”
    • Nodules are composed of hyphae and a cement-like substance.
    • Black piedra is caused by Piedraia hortae, characterized by hard, dark nodules.

    Tinea Capitis (Scalp Ringworm)

    • Microsporum audouinii and Microsporum ferrugineum are common causative agents.
    • Known forms:
      • Gray patch ringworm: prevalent in children, spreads easily.
      • Black dot ringworm: results in brittle hair that can break off.

    Tinea Pedis (Athlete’s Foot)

    • Common in shoe-wearing populations, affecting soles and toe web spaces.
    • Arises from contact with infected skin scales.
    • Genetic predisposition may increase susceptibility.
    • Severe cases present with extensive scaling and erythema.

    Distinguishing Dermatophyte Species

    • Geophilic: Microsporum gypseum found in soil.
    • Zoophilic: Microsporum canis associated with animals.
    • Subungual onychomycosis is a common nail infection form.

    Urease Test

    • Differentiates T. mentagrophytes from T. rubrum.
    • T. rubrum is urease negative or slow to react; T. mentagrophytes produces urease, changing medium color.

    Hyphal Structures and Confounding Species

    • Microconidia of T. rubrum are typically globose, while macroconidia appear clear and septated.
    • Trichosporon spp. presents as yellow or pale brown around hair shafts and can cause severe disease in immunocompromised patients.
    • Trichophyton tonsurans exhibits distorted macroconidia and balloon-shaped microconidia.

    Epidermophyton Floccosum Characteristics

    • Produces yellow to yellow-tan colonies with feathered edges.
    • Exhibits different growth properties when cultured on various media.

    Additional Notes

    • Wood's lamp positivity differs among dermatophytes: positive for Microsporum and Epidermophyton, negative for Trichophyton.
    • Microsporum audouinii colonies appear malted and velvety on non-fortified rice.

    Understanding these key points regarding the diagnosis and characteristics of various dermatophytes facilitates accurate clinical assessments and treatment strategies.

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    Superficial and Cutaneous Mycoses PDF

    Description

    Explore the diagnosis and identification of cutaneous mycoses, including various methods like direct KOH tests and staining techniques. This quiz focuses on the fungal diseases affecting keratinized tissues and the aspects of dermatophytes and dermatomycoses.

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