Fungal infections of skin and soft tissue Flashcards
What are the superficial mycoses?
Pityriasis versicolor, tinea nigra, black piedra, white piedra
What is the cause of pityriasis versicolor?
Malassezia furfur
Where is pityriasis versicolor normally found?
Areas of the body rich in sebaceous glands (head, trunk, upper back)
What are the clinical symptoms of pityriasis versicolor?
Numerous irregularly shaped yelllow / brown scaly patches; failure to tan
What is the diagnosis for pityriasis versicolor?
Direct observation - KOH prep (“spaghetti and meatballs”)
What is the cause of tinea nigra?
Exophiala werneckii
How is tinea nigra transmitted?
Traumatic inoculation / contamination with soil, sewage, wood, compost
What is the clinical presentation of tinea nigra?
Distinct oval-shaped brown/black lesions on hands and feet
How is tinea nigra diagnosed?
KOH prep on skin scrapings reveal two-celled yeast forms containing dark pigment
Where is black piedra most common? White piedra?
- Black - tropics 2. White - southern US
What are the clinical symptoms of black piedra?
Hard, firmly attached gritty nodules on hair, primarily scalp
What are the clinical symptoms of white piedra?
Soft, loosely attached white / light brown nodules usually on pubic or axillary hair, beards, eyebrows
What is the cause of cutaneous mycoses?
Dermatophytes
What are the three most clinically relevant dermatophytes?
Microsporum, trichophyton, epidermophyton
What do the dermatophytes use as a nutrient source?
Keratin