Superficial, Cutaneous, & Subcutaneous Mycoses Flashcards
(18 cards)
Fungal Structure
- Eukaryotic
- Cell wall w/ chitin and glucans
- Fungal membrane w/ ergosterol (non-human)
- No endotoxin
- Unicellular form: yeast
- Budding reproduction
- Filamentous multicellular form: mold
- Hyphae w/ apical growth
- Spores: mitosis or meiosis
- Dispersal and dormancy
- Dimorphic: both yeast
Microscopic diagnosis
- KOH solution: disolves tissue and visualizes hyphae
- Used to see dermatophytes & candida
- India Ink stains background leaving organism clear
- used to determine if a cell has a gelatinous capsule
- encapsulated yeast Cryptococcus spp
Culture diagnosis
- More sensitive than microscopy
- ID by appearance of mycelium and asexual spores
- Sabouraud’s agar: inhibits bacterial growth
- Standard blood culture bottles
Antifungals: Azoles
- Inhibit ergosterol synthesis
- Imidazoles: topical candidasis dermatophytes
- Clotrimazole, miconazole
- Triazoles: systemic and broad spectrum
- Fluconazole itraconazole, voriconazole
Antifungals: Polyenes
- Bind ergosterol- pore causing osmotic death
- Amphotericin B (IV systemic) broad specturm
- Renal toxicity
- Nystatin: topical
Antifungals: Echinocandins
- inhibit b-glucan synthesis; blocks cell wall
- caspofungin, anidulafungin, micafungin
- broad spectrum
Antifungals: Allylamines
- Ergosterol inhibitor
- Terbinafine: topical, oral: onychymycosis
- used for dermatophytes
- Butenafine: topical for dermatophytes
Immune response to fungi
- Endothelial cells: recognize fungi
- Dectin-1 of B-glucan binds definsins
- Neutrophils activated against mold such as aspergillus
- Th1 response to intracellular fungi
Superficial Mycoses
- Colonize outer keratinized surface
- Skin, hair, nails
- little to no immune response
- non-destructive
- mainly yeasts
Tinea (pityriasis) veriscolor
-Superficial Mycose
-Caused by yeast
-Malassezia furfur
-patches of skin w/ hyper- or hypo-pigmentation
-Wood’s lamp exam shows yellow-green fluorescence
-Spaghetti & meat ball appearance on microscope
*yeast-like cells w/ short pseudohyphae
-growth enhanced by adding olive oil
-Persistant & rarely self cures
Tx: topical therapy (azoles) or oral azoles if widespread
Tinea nigra
- Superficial Mycose
- dark brown spots on palms
- Hortaea werneckii
- Mold
White piedra
- Superficial mycose
- soft nodules composed of yeast cells and arthroconidia that encompass hair shafts.
- Trichosporon sp.
- Yeast
Cutaneous Mycoses
- Invasion of epidermis w/ inflammation
- Primarily caused by dermatophytes
- Breakdown keratin
- Invade skin, hair, nails
- Invade outermost layer of epidermis
- Stratum corneum
Tinea Infections
- Tinea capitus: ringworm on head
- Tinea corporis: ring worm of the body
- Tinea barbae: ringworm of the beard
- tinea cruris: ringworm of the groin
- Jock itch
- Tinea pedis: athlete’s foot
- Tinea unguium: onychomycosis: in nails
- Very hard to treat
- Transmission by direct or indirect contact
- TX: topical agents for most
- Oral azoles, terbiafine for hair or nail
Subcutaneous Mycoses
- Invasion of subcutaneous tissues
- Slow progression may req surgery
- All rare: trauma, rarely spread, hard to tx
Sporotrichosis
-Sporothrix schenckii
-Dimorphic, in soil and dead vegetation
*Pricked skin of gardener
-Primary lesion at site of injury
*Nodule grows, ulcerates and becomes painful
-Secondary lesions weeks later along lymphatics progress proximally
*Growing in macrophages
-Biopsy shows starburst pattern: eosinophilic granulomatous structure w/ radiating pattern
-Dx: culture
Tx: intraconazole for several weeks
Chromomycosis
- Chronic local infection causing warty/nodular outgrowths
- granulomatous inflammation
- Soil fungi after traumatic inoculation
- Tx: intraconazole or terbinafine + 5FC
- heat or cryotherapy to shrink lesions
Eumycotic mycetoma
- deep subcutaneous infection seen as swellings in sinus tracts
- Granulomas develop
- Pus and granules drain thru skin
- Caused by madurella, fusarium
- Dx: black granules in biopsy
- Tx: antifungal agents and local surgery can be tried
- Often ineffective
- frequent cure is amputation
