Fungal Infections of the Skin Flashcards
What type of structures do dermatophytes infect
Only superficial keratinized structures - skin, hair, nails
What are the three major genera of fungi
Epidermophyton, Trichophyton, Microsporum
Typical sites and characteristics of chronic infections
Warm/humid. Infection characterized by inflamed circular borders of papules and/or vesicles
What are the names of fungal infections of the head, body, crotch (Jock itch), and feet (Athlete’s foot) called?
Tinea - capitis, corporis, cruris, pedis
What are hypersensitive dermatophytid reactions?
Vesicles on fingers caused by hypersensitivity to circulating fungal antigen.
How are fungal infections generally diagnosed?
PPD type test with fungal antigen (trichophytin?), Microscopy with a KOH mount, Sabouraud’s agar (grows dermatophytes), Wood’s lamp (UV lamp that can fluoresce fungi)
Tx and prevention of dermatophyte infection
Topical antifungals (terbinafine [Lamisil], Undecylenic acid [Desenex], Miconazole [Micatin], Tolnaftate [Tinactin]), Oral antifungal (griseofulvin [Fulvicin]), keep skin dry and cool
Tinea Versicolor - Organism, Area of occurrence, Disease, Dx, Tx
Malassezia furfur, Hot and humid weather, Cutaneous mycosis - Superficial skin infection with hypopigmented areas with slight scaling/itching (cosmetic importance only). Microscopy w/ KOH mount and observe hyphae/yeasts, miconazole
Tinea Nigra, Organism, Area of occurrence, Disease, Dx, Tx
Cladosporium werneckii; Seen in southern US, Asia, Caribbean; Spores from soil enter skin lesion, Cutaneous mycosis - proliferate in keratinized skin layers and generate brown skin pigment; Sabouraud’s agar forms brown colony and KOH mount; Topical keratolytic agent (salicyclic acid) and topical azole
Sporotrichosis, Organism, Area of occurrence, Disease, Dx, Tx
Thermally dimorphic Sporothrix schenckii; found on vegetation (Rose gardener’s disease); Introduced by thorn puncture, yeast grows, drains thru lymphatics, may disseminate if immunosuppressed; Painless pustule/ulcer w/ Hx of gardening, tissue specimen - round/cigar-shaped budding yeast, culutre - hyphae with oval conidia in clusters at tip of slender conidiophores Resembles a daisy); Itraconazole (Sporanox); Prevention: Gardening gloves
Chromomycosis Organism, Area of occurrence, Disease, Dx, Tx
Dematiaceous fungi: Fonsecaea, Phialophora, Cladosporium; Soil in the tropics; Introduced into leg/feet with injury and gradually progresses to subcutaneous granulomatous disease; PE: Wartlike dark colored lesions w/ crusting abscesses along lymphatics, Lab: tissue specimen w/ dark brown, round fungal cells inside leukocytes/giant cells; Oral flucytosine or thiabendazole, shoes
Mycetoma Organism, Area of occurrence, Disease, Dx, Tx
Petriellidium or Madurella, Found in soil; Replicating fungi form pustular abscesses containing colored granules that drain thru local sinuses; Look similar to actinomycosis - actinomyces (bacteria) are small G(+), Eumycetoma larger and observable with fungal stains; AB and AF Tx oral azole plus IV amphotericin B + surgical excision of abscess
