Microbiology: Fungus - Cutaneous Mycoses

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cause: Tinea faciei

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Trichophyton

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Epidemiology: Tinea faciei

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-worldwide on human and non-human mammals

-transmitted by aerial dissemination on fomites

-patients usually 10-40 years old

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pathogenesis: Tinea faciei

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mycelia invade glabrous skin of face

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Sx: Tinea faciei

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scaling annular or circular lesions with raised margins and papules are formed

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Dx: Tinea faciei

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KOH and PAS stained preparations show hyphae with microconidia

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Tx: Tinea faciei

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miconazole

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cause: Tinea barbae

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Tricophyton

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epidemiology: Tinea barbae

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fomites, person to person by aerial dissemination

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pathogenesis: Tinea barbae

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mycelia grow into pores around hair shafts

hyphae growing into stratum corneum produce edema and leuokcytic infiltrations by releasing enzymes that destroy skin proteins

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sx: Tinea barbae

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mild superficial type- scaling lesions with vesiculopustular border on bearded areas of face and neck

deep pustular type- deep follicular pustules on bearded areas of face and neck that result in nodular keloids and kerions with alopecia and scarring

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dx: Tinea barbae

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KOH or PAS of lesion scrapings show different types of microconidia

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Tx: Tinea barbae

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griseofulvin

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cause: Tinea capitis-ecthothrix

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Microsporum species

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epidemiology: Tinea capitis-ecthothrix

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capitis ecthothrix- found worldwide

favosa: Africa and Europe

male infection common before puberty

female infection- after puberty

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All cutaneous mycoses are transmitted:

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person to person by aerial dissemination of fomites

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sx: tinea capitis ectothrix

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gray-patch ringworm on scalp eyelashes and eyebrows

lesions begin as coalesced papules in ring and develop into kerions (boggy areas of massive inflammation) or keloids (scars)

allergic rxn produce dermatophytics

alopecia bc of itching

keratomycosis (diseased cornea)

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Tinea favosa is a form of

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a form of tinea capitis caused by trichophyton schoenleinii that occurs when mycelia interact with scalp proteins producing dead cell masses in mats of hair and then develop into cup shaped skin crusts (scutula)

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dx:Tinea capitis-ecthothrix

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chains of macroconidia and hyphae are seen on KOH or PAS

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Tx: Tinea capitis-ecthothrix

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griseofulvin

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all cutaneous mycosis (all are the only ones that begin with tinea except tinea nigra) have partial protective immunity except

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tinea pedis

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cause: Tinea capitis-endothrix

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trichophyton species

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epidemiology: Tinea capitis-endothrix

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males have more infections than females

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Pathogenesis: Tinea capitis-endothrix

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conidia are found inside hair shafts

cuticle is involved, initial lesions are small and angular

cutaneous allergic eruptions occur

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sx: Tinea capitis-endothrix

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black dot ringworm- erythematous scaling, circular lesions with black dots

scutula (yellowish-brown, cup-shaped skin crusts)

chronic infection

alopecia

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dx: Tinea capitis-endothrix

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Conidia and hyphae are seen inside hair shafts on KOH or PAS

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Tx: Tinea capitis-endothrix

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Griseofulvin

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cause: Tinea corporis

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Microsporum and Trichophyton species and Epidermophyton floccosum

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pathogenesis: Tinea corporis

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hyphae or conidia infect horny layer of skin and spread circularly

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Sx: Tinea corporis

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rings of inflammation on glabrous skin of body that begin as dry and scaly patches which become pustular and crusty and can have extensive hyperkeratosis

annular type: annular type presents with small spreading circular areas of erythema that become scaly in center (chronic)

vesicular type- vesicles and pustules (not chronic)

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Dx: Tinea corporis

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KOH and PAS prep reveal mycelia and conidiospores

Microsporum canis ahs club shaped macroconidia

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tx: Tinea corporis

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terbinafine

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cause: Tinea imbricata

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Tricophyton concentricum

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Epidemiology: Tinea imbricata

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Tricophyton concentricum found in Pacific Islands, Southeast Asia and Central America

Found only in POLYNESIANS

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pathogenesis: Tinea imbricata

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masses of hyphae accumulate in cutaneous tissue

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Sx: Tinea imbricata

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brownish macropapules that gradually develop into concentrically arranged imbricated fissured rings on skin of arms and torso

chronic lesions

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Dx: Tinea imbricata

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PAS and KOH show flattened swollen hyphae with forked tips

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Tx: Tinea imbricata

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Miconazole

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Cause: Tinium unguium

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Epidermophyton floccosum and Tricophyton species

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epidemiology: Tinium unguium

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greatest in males after puberty

usually associated with Tinea pedis or Tinea manuum

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Pathogenesis: Tinium unguium

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starts under nail plate, hyphae growing out of nail plate into stratum corneum produces inflammation by releasing enzymes

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Sx: Tinea unguium

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produces soft friable keratin that loosens nail

leukonychia mycotica is nail invasion restricted to white patches or pits

invasive subungual dermatophytosis occurs when lateral or distal edges of nail are first involved and develop into a nail plate that is brittle and friable with cracks and are brown or black in color

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dx: Tinium unguium

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Hyphae and macroconidia in PAS and KOH

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Tx: Tinium unguium

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Terbafine

most infections are chronic

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cause: Tinea manuum

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Epidermophyton floccosum, microsporum and trichophyton species

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epidemiology: Tinea manuum

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most prevalent in males, associated with Tinea pedis

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pathogenesis: Tinea manuum

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maceration of skin

infection of palms and fingers results in lesions that begin as exfoliative, erythematous, scaly sheets of skin that become vesicular red circumscribed patches

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sx: Tinea manuum

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patients have diffuse hyperkeratosis of palms and fingers

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Dx: Tinea manuum

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KOH and PAS of skin show hyphae and macroconidia

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Tx: Tinea manuum

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Miconazole

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cause: Tinea cruris

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Epidermophyton floccosum and triophyton species

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Epidemiology: Tinea cruris

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20 to 30 year old males

often associated with Tinea pedis

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Pathogenesis: Tinea cruris

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hypae invade moist areas of the groin and perianal areas

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Sx: Tinea cruris

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jock itch

serpingous well marginated erythematous lesions with raised borders

older lesions become leather like

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Dx: Tinea cruris

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Epidermophyton and tricophyton have club shaped macroconidia with smooth walls

Epidermophyton floccosum does not produce microconidia

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Tx: Tinea cruris

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Terbinafine

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cause: Tinea pedis

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Epidermophyton floccosum and Trichophyton

mycoses of feet

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Epidemiology: Tinea pedis

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athletes foot

most often seen adult males

frequently found in pool decks and shower rooms

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Pathogenesis: Tinea pedis

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breakdown of host's skin defenses promotes invasion which is localized to keratinized skin

chronic papulosquamous and hyperkeratotic skin

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Sx: Tinea pedis

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itching intertriginous dermatitis with peeling, maceration and fissuring of skin between 3rd 4th or 5th toes

vesicles or bullae on dorsal surface of foot

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Dx: PAS and KOH

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hyphae and macro or microconidia

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Tx: Tinea pedis

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Terbinafine