58. Mucosal and Cutaneous Fungi Flashcards Preview

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Flashcards in 58. Mucosal and Cutaneous Fungi Deck (22)


- Microsporum spp (more common worldwide, can’t cause onychomycosis/tinea unguium)
- epidermophyton floccosum (tinea cruris only)
- Trichophyton spp (most common in USA)


pathogenesis of dermatophytosis?

use keratin as a nutrient source, involvement of underlying and surrounding tissues results from allergic or inflammatory host responses to fungi, cellular immunity is a key host defense (HIV ), and subtleties in iron metabolism


dermatophytes by environmental reservoir?

• Anthropophilic species are adapted to live in humans and thus elicit a more mild response (T.tonsurans)

Zoophilic species are adapted to live in animals and thus elicit a more severe response (M. canis  take pet to vet for treatment)

Geophilic species are adapted to the soil and commonly infect avid gardeners (M.gypseum)


onchomycosis is caused by what?

T.rubrum or T.mentagrophytes


onchomytosis causes what?

Source of pain, ambulatory dysfuntion, and paronychia (skin infection near the nails, commonly S.aureus)


increased risk for onchomytosis?

• Increased risk: diabetes, HIV/AIDS, other compromised hosts, elderly


3 clinical types of onchomycosis?

Proximal subungual (PSO)
- T.rubrum
- Immunocompromised hosts and is an early indicator of HIV infection
- Mechanism of invasion: infection enters at the cuticle and involves the proximal nail bed; spreads distally to eventually invole the entire nail plate if untreated

Distal subungual (DSO) (90% of cases)
- T.rubrum (also T.tonsurans, T.mentagrophytes, and E.floccosum)
- Mechanism of invasion: hyphae enter distally under the nail plate and spread proximally, digesting the stratum corneum of the nail bed as well as the nail plate
- Subungual hyperkeratosis, paronychia, and onycholysis can occur as the infection spreads

White superficial (WSO) (only 10% of cases)
- T.mentagrophytes
- Dorsal surface of the nail plate is attacked, resulting in minimal inflammation as viable tissue is not involved


lab testing for onchomycosis?

o KOH w/calcofluor direct exam and culture of the nail is definitive diagnostic tool


treatment/prevention for onchomycosis?

o Oral therapy: terbinafine, itraconazole


superficial mycoses?

Superficial Mycoses: fungal infections of the superficial stratum corneum that do not elicit a host response

Tinea Versicolor: superficial mycotic infection of young and middle-aged adults caused by lipophilic yeast Malessezia furfur usu involving upper trunk, neck, and arms (dx w/pale yellow flourescense on Wood’s light exam or spaghetti and meatballs on KOH microscopy)

Also recently, M.furfur has been implicated in other conditions like pityriasis folliculitis, seborrheic dermatitis, atropic dermatitis, and dandruff

Tx: scraping, topical selenium sulfide shampoo or short course PO itraconazole/fluconazole


tinea capitis patients infected?

- infants, children, and young adolescents
- urban infection usu African American or Hispanic preschoolers (w/poor access to healthcare and crowded living)


tinea capitis pathophysiology?

- ectothrix: arthroconidia form on the outside of the hair shaft and the cuticle is destroyed (M. canis, M.gypsium, T.equinum)
- Endothrix: arthroconidia form within the hair shaft, leaving the cuticle intact (T.tonsurans)


tinea capitis pathology?

- primary lesions may be papules, pustules, plaques or nodules on the scalp. Inflammation results in scaling, alopecia, erythema, exudate and edema
- kerion forms as a result of increased cell-mediated immune response, demonstrated by severe inflammation, hair loss and cervical lymphadenopathy
- breakage of hairs = black dot alopecia


tinea capitis disease?

Ectothrix: more inflammatory but better prognosis

Endothrix: irreversible alopecia (less inflammatory but more destructive)


tinea captitis dx?

- KOH exam of extracted hair if caused by Trichophyton species, as spores can attach or reside on the hair shaft. Culture the extracted hair (not painful because follicle already destroyed)
- if caused by M.audouinii or M.canis can also test re: fluoresces blue-green under Wood’s light examination


tinea captitis treatment?

Oral antifungal: terbinafine, ketoconazole, itraconazole, or fluconazole plus reduce fungal shedding with ketoconazole shampoo and prevent spread to family members by cleaning contaminated combs and brushes, selenium sulfide lotion for family members


tinea capitis bugs?

- Trichophyton (tonsurans) (80%)
- Microsporum (more common worldwide)


tinea corporis pathology?

- ringworm (erythematous, round, scaly plaque or patch w/a red, raised, advancing border – edge can contain papules or pustules)


tinea dx (besides capitis)?

KOH or calcofluor preparation of scale scraped from leading edge of the lesion (KOH dissolves squamous epith to leave just hyphae)
- cx to confirm

Any dermatophyte growth found is a pathology/is significant!


tinea tx (besides capitis)?

- treat the pet/animal
- topical therapy:
Miconazole, Clotrimazole, Ciclopirox, econazole, ketoconazole, terbinafine
If exensive/severe: PO fluconazole or terbinafine

Nafitine also for tinea pedis


tinea pedis patients infected?

- most common dermatophytosis (70% adults)
- troops
- athletes


tinea pedis disease?

- interdigital
- moccasin (painful, overt)
- vesiculobullous
(may present with onchomycosis)