Flashcards in skin 9: keratin layers- general Tinea Deck (40):
Dermatophytes - Tineas
infections of the skin, nails or hair produced by keratinolytic (dermatophytic) fungi. Commonly referred to as tinea or "ringworm" infections.
generally named for the anatomic site affected
Tinea capitis: ringworm of the scalp and hair
Tinea pedis: athlete's foot
Tinea cruris: jock itch
Tinea unguium: oncychomycosis (nail infections)
Tinea manuum: ringworm of the hand
Tinea barbae: barber's itch
Tinea corporis: ringworm of the smooth skin (i.e. trunk)
Tinea faciei: ringworm of the non-bearded areas of the face
Tinea infection details
*Keratin is required for growth*
*do not usually invade living tissue*
Infections can occur at multiple sites.
Different organisms can cause the same tinea
presentation may vary with org/source
Disease is confined to the keratinized layers of the skin, primarily the epidermis.
Microsporum: Spindle-shaped macroconidia. Involves hair and skin.
Epidermophyton: Clavate-shaped macroconidia. Involves skin and nails.
Trichophyton: Elongated, pencil-shaped macroconidia. Involves hair, skin, and nails.
"Microsporum no nails, Epidermophyton no hair, Trichophyton everywhere"
True incidence is unknown. It is estimated that the
prevalence is 20% of the global population. Studies report that 90% of all males have at least one bout.
The incidence and prevalence is lower in females.
Tineas are globally distributed.
Cross-infection in families is 35-50% which is particularly important for infections in children.
Animals also act as reservoirs.
Tinea (ringworm) is transmitted indirectly via ??
fallen hairs and desquamated epithelium more often than by direct bodily contact.
Sources of the organisms include: Contaminated barbershop instruments, hats, combs, bedding clothing, towels, furniture, theater seats, contaminated floors, infected mother-to-child, cats and dogs, cattle, rats, field mice, soil, etc.
About 10% of the infectious material (w. tinea) was transferred from ??
contaminated textiles to sterile textiles during storage in a clothes basket simulation indicating a high infection risk during storage
While laundry wash temperature of 86oF will kill Candida spp., Washing at 140
oF will eliminated T. rubrum and C. albicans.
Tinea Age and gender??
More common in males and post-pubescents
Warmer months in general
Predisposing factors parallel that of pityriasis versicolor with the addition of obesity. Hydration and humidity are significant factors.
Tinea pathogenesis: Dermatophyte colonization is limited to ??
the keratinized tissue of the epidermis
Although the cornified layers of the skin lack a specific immune response, *both humoral and CMI* immune systems and innate immunity act to limit invasion.
major defenses against Tinea
*2-macroglobulin keratinase inhibitor, unsaturated transferrin*, epidermal desquamation, lymphocytes, macrophages, epidermal Langerhans cells, dermal dendritic cells, neutrophils and mast cells.
*CMI is the major defense against dematophytic infections and fungal infections in general*
Tinea Allergic manifestation
sterile vesicle which can appear at a site distinct from the focus of infection.
This sign indicates a secondary inflammatory reaction as a result of an active CMI immune response.
would you rather have "bad" or mild infection? "bad!": inflammatory infection implies immune response
-mild implies the organism as adapted to humans in order to self-preserve
Tinea s/s: manifestations of mycotic agents are dependent on source of the organism
Geophilic: Normally inhabit the soil where they live on keratin that is shed by animals
Zoophilic: Infect or are carried by animals, but they can also infect humans who are in close contact with animals
Anthropophilic: Species whose principle reservoirs are human nails, skin and hair. rarely infect animals and cannot survive in the soil.
Acute vs. chronic dermatophytoses infections: etiology
Acute: Geophilic or zoophilic species
Chronic: Anthropophilic species
Acute vs. chronic dermatophytoses infections: inflammation
Acute vs. chronic dermatophytoses infections:s/s
acute: Erythema, *vesicles*, pruritus, *pain*
chronic: Erythema, *scaling*, pruritus
Acute vs. chronic dermatophytoses infections: Spread of lesions
acute: Usually limited
chronic: Often extensive
Acute vs. chronic dermatophytoses infections: duration
Acute vs. chronic dermatophytoses infections: DTH response
Acute vs. chronic dermatophytoses infections: prognosis (response to tx)
Acute vs. chronic dermatophytoses infections:: recurrence
Dermatophyte/Tinea dx: made by ??
taking skin scrapings for microscopy and culture.
Because of misdx, scrapings to make the dx have often been delayed for months.
If steroid cream has recently been applied, there is little surface scale to scrape off so results: inadequate or negative. A few days after stopping the steroid cream, the rash becomes very inflamed and more fungal elements may be seen on microscopy than usual. The responsible organism generally grows promptly in culture.
Tinea office/lab tests
KOH prep of hair, skin, or nail scrapings.(Cellufluor white aids in staining). Culture hair skin, or nail scrapings on Dermatophyte Test Medium or Sabouraud-glucose agar containing chloramphenicol and cycloheximide.
(when too deep to use Wood's lamp)
Dermatophytes that fluoresce apple to blue green w. Wood's lamp
Microsporum and superficial Pityriasis (Mala. furfur)
Dermatophytes that fluoresce a brilliant coral red w. Wood's lamp
Erythrasma, caused by the bacterium Corynebacterium minutissimum
(in a brown, scaly rash in the scrotum or axilla)
Dermatophytes that do not fluoresce fluoresce w. Wood's lamp
tinea cruris or cutaneous candidal infections
(a brown, scaly rash in the scrotum or axilla)
Differentials for Annular Skin Eruptions, OR "All Rings Aren't Ringworm"
Fungal eruptions are one of the most common causes of ring shaped eruptions, however, there are at least 24 other disorders that can result in rings on the skin.
In general, in classic ringworm, there is ??
an annular lesion with an active border that exhibits erythema and scaling; however, there can also be significant inflammation, vesicles or minimal inflammation.
presentation in part depends on the source of the organism.
how to dx Tineas
*No findings are pathognomonic for superficial tinea infections, thus lab testing needed to confirm dx*
locationof the lesions also can help ID org
A dermatophytosis can most likely be ruled out if a patient has ??
In this situation, the more probable diagnosis is a ??
mucosal involvement with an adjacent red, scaly skin rash.
candidal infection such as perlèche (if single or multiple fissures are present in the corners of the mouth) or vulvovaginitis or balanitis (if lesions are present in the genital mucosa).
Tinea ddx: Infectious Etiology.
coalesced HSV lesions,
lyme borreliosis (erythema migrans),
secondary syphilitic lesions,
HPV coalesced papules (verruga vulgaris).
Tinea ddx: Papulosquamous diseases.
Pityriasis rosea (cause unknown thought to be a virus),
eczema (cause unknown but many patients are atopic),
psoriasis (cause unknown),
lichen planus (cause unknown but may be drug related),
urticaria (multiple causes), erythema multiforme (viral infections, e.g. HSV, and many drugs),
drug-induced eruptions, SLE, sarcoidosis, etc.
Tinea incognito: tinea when ?? ("tinea in disguise")
clinical appearance has been altered by inappropriate treatment, usually a topical steroid cream.
initial improvement-->spread of the organisms due to local conditions of immunosuppression and an associated skin discoloration.
Compared with an untreated tinea, tinea incognito: ??
Has a less raised margin, is less scaly, more pustular, more extensive, and more irritable.
may also be secondary changes caused by long term use of a topical steroid such as: Atrophy (thin skin, stretch marks [striae] in the skin folds); purpura and telangiectasia (broken blood vessels).
Remove infected and dead epithelial structure. Apply topical (palliative or antifungal) agents (depends on host's reaction to fungus and area involved).
Tinea considerations for choice of antifungal agent include ??
type of infection
location of infection
severity of infection
occupation of patient
overall patient health
Tinea solution tx
Solutions include potassium permanganate 1:5,000, salicylic acid or 20% sodium hyposulfite. Gentian violet (vaginal candidiasis, oral thrush).
Tinea ointment/powder tx
Ointments at night, and powders by day include Whitfield's (salicylic acid and benzoic acid), sulfur, tolnaftate (Tinactin)R, DesenexR (undecylenic acid or zinc undecylenate), haloprogin, clotrimazole (Mycelex)R, griseofulvin, imidazole derivatives, naftin.
tx for severe dermatophytic infections
lamisil, itraconzole griseofulvin or ketoconazole is administered orally.