questions 3

Cutaneous and Subcutaneous Mycoses

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Topic updated on 11/19/16 4:00am

Malassezia furfur
  • PhotoDiseases
    • tinea versicolor   
      • a superficial infection of keratinized cells
      • leads to hypopigmented spots on skin
        • "blotchy suntan"
      • most commonly found in hot, humid weather
    • fungemia in premature infants on IV lipid supplements
  • Pathogenesis
    • degradation of lipids leads to production of acids, and eventual destruction of melanocytes
  • Diagnostic testing 
    • best initial test: KOH test of the skin
      • "spaghetti and meatball" appearance on KOH mount of skin 
        • due to yeast clusters + short, curved, septate hyphae
    • most accurate test: fungal culture (usually not necessary)
  • Treatment
    • topical miconazole
    • selenium sulfide (Selsun)
Dermatophytes (Trichophyton, Microsporum, Epidermophyton)
  • PhotoDiseases
    • tineas (ringworm)
      • pruritic, ringlike skin lesions that may also involve hair shaft or nails
      • types include
        • tinea capitis (scalp)
        • tinea pedis (athlete's foot)
        • tinea cruris (jock itch)
        • tinea corporis (glabrous skin)
        • tinea unguium (nail) (also known as onychomycosis)
    • ID reaction
      • hypersensitivity response to fungal antigens
  • Pathogenesis
    • Trichophyton
      • infects skin, hair, nails
    • Microsporum
      • infects hair, skin
      • pets are a reservoir
    • Epidermophyton
      • infects nails, skin
    • infections do not disseminate
  • Diagnostic tests
    • monomorphic filamentous fungi
    • best initial test: arthroconidia and hyphae seen on KOH mount of nail or skin scrapings
    • fluoresces yellow-green under Wood lamp 
    • most accurate test: fungal culture
  • Treatment
    • keep infected area dry
    • imidazoles (topical or oral)
    • onychomycosis or tinea capitis
      • oral terbinafine (hepatotoxic, monitor liver function tests) or griseofulvin (outdated treatment)
Sporothrix schenckii
  •  Diseases
    • sporotrichosis (rose gardner's disease)
      • nodular lesions on skin
        • starts at point of entry
        • progress proximally along lymph nodes in a process called ascending lymphagitis 
      • ulcers develop as disease progresses
      • little systemic involvement
    • pulmonary sporotrichosis
      • seen in alcoholics and homeless
  • Pathogenesis
    • lives on plants
    • traumatically implanted into humans
      • e.g. by a rose thorn
    • seen in florists, gardners, basket weavers, flower enthusiasts
  • Laboratory
    • dimorphic
      • cigar-shaped yeast seen in pus at 37°C
      • septate hyphae and conidia at 25°C
  • Treatment
    • itraconazole
    • potassium iodide


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