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Questions and Answers
What type of infection does pityriasis versicolor represent?
What type of infection does pityriasis versicolor represent?
Which species is primarily responsible for causing pityriasis versicolor?
Which species is primarily responsible for causing pityriasis versicolor?
Which describes the pigmentation changes in pityriasis versicolor?
Which describes the pigmentation changes in pityriasis versicolor?
Where on the body is pityriasis versicolor most commonly found?
Where on the body is pityriasis versicolor most commonly found?
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What is a characteristic of superficial mycoses?
What is a characteristic of superficial mycoses?
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What environmental condition is associated with a higher incidence of pityriasis versicolor?
What environmental condition is associated with a higher incidence of pityriasis versicolor?
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How do patients typically feel about their condition when they have superficial mycoses?
How do patients typically feel about their condition when they have superficial mycoses?
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What type of tissue do superficial mycoses invade?
What type of tissue do superficial mycoses invade?
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What is a common feature of Pityriasis versicolor?
What is a common feature of Pityriasis versicolor?
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Which method is used for the laboratory diagnosis of Pityriasis versicolor?
Which method is used for the laboratory diagnosis of Pityriasis versicolor?
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Which organism is responsible for Tinea nigra?
Which organism is responsible for Tinea nigra?
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What is a common appearance in Tinea nigra diagnosis?
What is a common appearance in Tinea nigra diagnosis?
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What is an effective topical agent for treating Tinea versicolor?
What is an effective topical agent for treating Tinea versicolor?
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Which media is used to culture skin scrapings for diagnosing Tinea nigra?
Which media is used to culture skin scrapings for diagnosing Tinea nigra?
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What characterizes Piedra infections?
What characterizes Piedra infections?
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What is the correct size of yeast-like cells found in Pityriasis versicolor?
What is the correct size of yeast-like cells found in Pityriasis versicolor?
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What is the primary causative agent of white piedra?
What is the primary causative agent of white piedra?
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What characteristic distinguishes white piedra from black piedra?
What characteristic distinguishes white piedra from black piedra?
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Which treatment is specifically mentioned for fungal keratitis related to Candida infections?
Which treatment is specifically mentioned for fungal keratitis related to Candida infections?
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What are common symptoms of otomycosis?
What are common symptoms of otomycosis?
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Where is white piedra most commonly found on the body?
Where is white piedra most commonly found on the body?
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What is a primary cause of keratomycosis?
What is a primary cause of keratomycosis?
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What is the appearance of nodules in white piedra?
What is the appearance of nodules in white piedra?
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What type of organism primarily causes otomycosis?
What type of organism primarily causes otomycosis?
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What are the two recognized varieties of piedra?
What are the two recognized varieties of piedra?
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Which characteristic describes the nodules of black piedra?
Which characteristic describes the nodules of black piedra?
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How is black piedra diagnosed microscopically?
How is black piedra diagnosed microscopically?
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What is the primary therapy method for treating black piedra?
What is the primary therapy method for treating black piedra?
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What is the characteristic color of colonies of Piedra hortae when cultured?
What is the characteristic color of colonies of Piedra hortae when cultured?
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What other treatment options are available for black piedra?
What other treatment options are available for black piedra?
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What structures may be found within the nodules of black piedra?
What structures may be found within the nodules of black piedra?
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Which infection site is primarily affected by black piedra?
Which infection site is primarily affected by black piedra?
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Study Notes
Superficial Mycoses
- Infections of the outermost layer of the skin, hair, dead skin, and lipid secretions.
- Fungi causing these infections live as saprophytes, they do not invade living tissue.
- Often harmless, patients may be unaware of the infection.
Common Types of Superficial Mycoses
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Pityriasis versicolor: Chronic superficial infection of the stratum corneum caused by Malassezia globosa and Malassezia furfur.
- Characterized by hypopigmentation or hyperpigmentation of skin on the neck, shoulders, chest, and back.
- Usually presents as asymptomatic patches of discolored macules, varying in size, shape, and color.
- Most common sites: chest, upper back, shoulders, upper arms, and abdomen.
- Hair shaft and nails are not infected.
- More common in hot, humid climates or those who sweat heavily.
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Tinea nigra: A superficial fungal infection of the skin caused by Exophiala werneckii.
- Characterized by brown to black macules typically on the palms of the hands, and occasionally on the soles and other skin surfaces.
- Worldwide distribution, but more common in tropical regions.
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Black piedra: Colonization of the hair shaft resulting in firm, irregular nodules.
- Caused by Piedra hortae.
- Nodules are a loose aggregate of hyphae and arthroconidia.
- Affects hairs of the scalp, body, and genital areas.
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White piedra: Similar to black piedra but with soft, mucilaginous, white greenish-yellow to light brown nodules.
- Caused by Trichosporon beigelii.
- Nodules are usually thickest at the center but may vary in shape and size.
- The fungus mass can easily be pulled off the hair shaft.
- Affects hairs of genital area, beards, mustaches, and sometimes scalp, eyebrows, or eyelashes.
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Mycotic keratitis (Keratomcosis): A fungal infection of the cornea (the anterior part of the eye).
- Causes inflammation of the cornea (keratitis).
- Caused by Aspergillus fumigatus, Fusarium spp., and Candida spp.
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Otomycosis: A fungal ear infection, a superficial infection of the outer ear canal.
- More common in tropical countries.
- Characterized by malodorous discharge, inflammation, pruritus, scaling, and severe discomfort.
Pityriasis versicolor
- Malassezia yeasts grow sparsely in seborrhoeic areas without causing rashes.
- The yeasts induce enlarged melanosomes (pigment granules) within basal melanocytes in the brown type of pityriasis versicolor.
Diagnosis of Superficial Mycoses
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Pityriasis versicolor:
- Direct microscopy: Skin scrapings mounted in 10% KOH, glycerol, and Parker ink solution: look for thick-walled, round, budding yeast-like cells and short angular hyphal forms up to 8um in diameter (spaghetti and meatballs).
- Culture: Sabouraud's dextrose agar (SDA) supplemented with cycloheximide (actidione) and olive oil.
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Tinea nigra:
- Direct microscopy: Skin scrapings mounted in 10% KOH: look for pigmented brown to dark olivaceous (dematiaceous) septate hyphal elements and yeast cells producing annello conidia typical of Hortaea werneckii.
- Culture: Skin scrapings inoculated on Sabouraud's dextrose agar: observe the appearance of dark (dematiaceous) septate hyphae.
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Black piedra:
- Direct microscopy: Hairs examined with 10% KOH and Parker ink or calcofluor white: observe darkly pigmented nodules that may partially or completely surround the hair shaft.
- Culture: Hair fragments cultured on Sabouraud's dextrose agar: look for dark, brown-black colonies of Piedra hortae (takes 2-3 weeks to grow).
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White piedra:
- Direct microscopy: Hairs examined with 10% KOH: observe soft, less discrete nodules lacking dark coloration compared to black piedra.
- Culture: Observe white to cream colonies of Trichosporon beigelii.
Treatment of Superficial Mycoses
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Pityriasis versicolor:
- Topical agents: selenium sulfide, sodium sulfacetamide, azole and allylamine antifungals.
- Oral agents: ketoconazole, fluconazole, and itraconazole.
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Tinea nigra:
- Topical antifungal creams.
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Black piedra:
- Shaving affected areas.
- Topical applications: salicylic acid, 2% formaldehyde, azole creams.
- Oral therapy: ketoconazole or terbinafine.
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White piedra:
- Ketoconazole, 2% selenium, amphotericin B.
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Mycotic keratitis:
- Fluconazole ophthalmic solution for Candida infection.
- Amphotericin B eye drops.
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Otomycosis:
- Often treated with topical antifungal medications.
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Description
Explore the fascinating world of superficial mycoses, including common infections like Pityriasis versicolor and Tinea nigra. This quiz covers the characteristics, symptoms, and common locations of these fungal infections that primarily affect the outer layers of the skin. Understand how these fungi thrive without invading living tissues and their prevalence in various climates.
