Transcript Dermatophyte fungal infections

Superficial Fungal
Infections
Dermatophyte fungal infections
• Dermatophytes are a group of fungi (ringworm) that only
infect and survive on the stratum corneum, hair, and nails
(dead keratin).
• Cannot survive on mucosal surfaces where keratin does not
form.
• Very rarely, dermatophytes undergo deep local invasion
and multivisceral dissemination in the immunosuppressed.
• Genetic susceptibility may predispose to dermatophyte
infection.
• The ringworm fungi belong to three genera: Microsporum,
Trichophyton, and Epidermophyton.
• Anthropophilic dermatophytes like Trichophyton ruburm, T.
tonsurans, T. violaceum and Microsporum audouinii
• Zoophilic dermatophytes like M. canis and T. verrucosum
• Geophilic dermatophytes like M. gypseum
• In general, zoophilic and geophilic dermatophytes elicit a
severe inflammatory responses VS the anthropophilc ones.
The active border
• One very characteristic pattern of inflammation is
the active border of infection.
• The highest numbers of hyphae are located in the
active border, so samples are taken from here.
• Typically the active border is scaly, red, and slightly
elevated.
• Vesicles appear at the active border when
inflammation is intense.
• This pattern is present in all locations except the
palms and soles.
Tinea of the foot (tinea pedis, athlete’s foot)
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The feet are the most common area infected by dermatophytes?
Trichophyton rubrum is the usual pathogen.
Usually associated with fungal toenail infection.
Itching is variable in the four clinical types.
1. The classic “ringworm” pattern
2. Interdigital tinea pedis (toe web infection)
• The web between the fourth and fifth toes is most commonly
involved.
• Tight-fitting shoes are a predisposing factor.
• The toe web can become dry, scaly, and fissured or white,
macerated, and wet.
• The bacterial flora is unchanged in the dry scaly pattern.
• The macerated pattern occurs from an interaction of bacteria and
fungus.
• Extension out of the web space onto the sole or dorsum of the foot
is common.
3. Chronic scaly infection of the
plantar surface
• Plantar hyperkeratotic or moccasin-type
tinea pedis is a particularly chronic form
of tinea that is resistant to treatment.
• Clinically…
• The hands may be similarly infected (two
feet-one hand syndrome).
4. Acute vesicular tinea pedis
• A highly inflammatory fungal infection.
• Occlusive shoes predispose to it.
• It often originates from a more chronic web
infection.
• A few or many vesicles evolve rapidly on the sole
or on the dorsum of the foot.
• Specimens for KOH examination are taken from
where?
Treatment
• Terbinafine 1% cream twice daily for 1 week in the
interdigital type.
• Econazole is excellent in the macerated interdigital TP.
• Recurrence is prevented by wearing wider shoes and
expanding the web space with a small strand of lamb’s
wool. Powders(not necessarily medicated) absorb
moisture.
• Oral terbinafine 250 mg daily for 2 weeks in the
hyperkeratotic type and other types of TP.
• Acute vesicular tinea pedis responds to wet
compresses, oral antifungal and oral antibiotics.
• Id reaction requires wet dressings, group V topical
steroids, and occasionally systemic steroids.
Tinea of the groin
• Tinea of the groin (tinea cruris) occurs in the summer
as well as in the winter.
• Warm, moist environment.
• Men > women; children rarely develop tinea cruris.
• The lesions are most often unilateral (unlike candida)
and begin in the crural fold.
• Clinically…
• The infection occasionally migrates to the buttock and
gluteal cleft area.
• Involvement of the scrotum is unusual (unlike candida).
• DDx: intertrigo, erythrasma, inverse psoriasis,
seborrheic dermatitis and candidaisis.
• Treatment…
Tinea of the body and face
• Tinea of the face (excluding the beard area in
men), trunk, and limbs is called tinea corporis.
• There is a broad range of manifestations, with
lesions varying in size, degree of inflammation,
and depth of involvement due to differences in
host immunity and the species of fungus.
• Clinically…
• Deep inflamatory lesions are caused by zoophilic
fungi.
• Treatment…
Tinea of the hand
• Tinea of the dorsal aspect of the hand (tinea
manuum) has all of the features of tinea corporis.
• Tinea of the palm has the same appearance as
the dry, diffuse, keratotic form of tinea of the
sole.
• The dry keratotic form may be asymptomatic.
• Tinea of the palms is frequently seen in
association with tinea pedis (pattern).
• Fingernail infection often accompanies tinea
manuum.
• Treatment…
Tinea incognito
• Fungal infections treated with topical steroids often
lose some (or sometimes all) of their characteristics.
• Tinea of the hand, body, face and groin are often
misdiagnosed as eczema and treated with topical
steroids.
• Topical steroids reduce inflammation giving false
impression of improvement.
• In the mean time, the fungus flourishes. Why?
• Treatment is stopped, the rash returns, but by this time
it has changed. How?
• Intensity of itching is variable.
• Hyphae are easily seen with KOH exam. several days
after stopping the use of steroids when scaling
reappears.
Tinea of the scalp
• Tinea capitis occurs most frequently in prepubertal
children.
• The causative species vary from country to country, but
anthropophilic species predominate in most areas.
• It is most common in areas of poverty and crowded
living conditions.
• Unlike other fungal infections, tinea capitis may be
contagious by direct contact and as well as
contaminated clothing or wear; therefore close contact
is not necessary for transmission and isolation is
justified.
• Asymptomatic scalp carriage of dermatophytes can
occur and may continue indefinitely.
Patterns of invasion
ENDOTHRIX PATTERN OF INVASION
• Endothrix hair invasion is produced predominantly by T.
tonsurans, T. soudanense, and T. violaceum.
• The fungus grows completely within the hair shaft, and the
cuticle surface of the hair remains.
• Endothrix infections tend to progress, become chronic, and
may last into adult life.
ECTOTHRIX PATTERN OF INVASION
• Ectothrix hair invasion is associated with M. audouinii, M.
canis, and T. verrucosum.
• The hyphae break through the surface of the hair shaft
(cuticle) and form a sheath.
• Therefore, spores are located inside and outside the hair
shaft.
Clinical infection patterns
• There may be multiple cases within a family, and each
person may have a different infection pattern which may be
due to specific host T-lymphocyte response.
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Noninflammatory grey patch pattern
Clinically…
DDx: Psoriaisis, atopic dermatitis, seborrheic dermatitis.
Negative Trichophyton Ag skin test.
2. Noninflammatory black dot pattern
• Lack of inflammation may be explained by the fact that
cell-mediated immunity to Trichophyton antigen skin tests
is negative in these patients.
• Clinically…
• DDx: Alopecia areata, trichotillomania.
3. Inflammatory tinea capitis (kerion)
• Most patients have a positive skin test to the
Trichophyton antigen, suggesting that the
patient’s immune response may be responsible
for intense inflammation.
• Clinically…
• Lymphadenopathy
• DDx: Abscess, neoplasm.
• KOH mounts and fungal cultures are often
negative because of destruction of fungal
structures by inflammation.
• Scarring alopecia may occur.
4. Seborrheic dermatitis type
• This type is the most difficult to diagnosis
because it resembles dandruff.
• Clinically…
• DDx: Psoriasis, atopic and seborrheic dermatitis.
5. Pustular type
• Follicular pustules may be sparse or numerous.
• No scale or significant hair loss (slight).
• Lymphadenopathy
• DDx: Bacterial folliculitis, dissecting folliculitis.
• Cultures and KOH wet mounts may be negative.
Investigations
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Collection of samples (brush)
KOH
Culture
Wood’s lamp: Blue-green fluorescence of
hair—only M. canis and M. audouinii have this
feature. Scale and skin do not fluoresce.
Treatment of tinea capitis
• Topical antifungals are not recommended and not effective.
• Systemic therapy is the sole treatment.
Griseofulvin
• Is the current drug of choice in children (safe, least known
drug interactions, well tolerated, suspension form).
• It is fungistatic and antiinflammatory.
• Dose: 15-25 mg/kg/day.
• Fatty foods enhance absorption.
• Prolonged treatment required (2-3 months).
• Side effects: GI upset, headache, dizziness, insomnia,
cutaneous eruptions, photosensitivity.
• Contraindications…
Trebinafine
• Fungicidal.
• Dose: 125-250 mg/day for 4 weeks.
• Food enhances absorption by 20%.
• Side effects: GI upset, alteration in taste,
cutaneous eruptions, neutropenia,
agranulocytosis, abnormal LFTs (3.5-7%).
• No suspension formulation.
Itraconazole
Additional measures
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Shaving the head
Exclusion from school
Familial screening (including pets)
Dealing with carriers
Cleansing of fomites
Steroids: The use of corticosteroids (both oral
and topical) for inflammatory varieties (e.g.,
kerions and severe id reactions) is
controversial, but may help to reduce itching
and general discomfort.
Tinea of the beard
• Tinea barbae is a dermatophytic infection confined to the
coarse hair-bearing beard and mustache areas in men.
• Usually occurs after minor trauma such as shaving.
• Like tinea capitis, the hairs are almost always infected and
easily removed.
• Hairs in bacterial folliculitis resist removal.
• Superficial follicular infection, resembles the annular tinea
corporis.
• Deep follicular infection, resembles bacterial folliculitis but
evolves slowly and is usually restricted to one area of the
beard.
• Bacterial folliculitis spreads rapidly over wide areas after
shaving.
• Zoophilic T. mentagrophytes and T. verrucosum are the
most common pathogens.
• Treatment: same as tinea capitis, oral agents are required.
Onychomycosis
• Onychomycosis is a fungal infection of the nail plate and/or
nail bed.
• It accounts for about 50% of all nail diseases and
approximately 30% of all superficial fungal infections.
• The worldwide prevalence is high and increasing.
• Onychomycosis is a significant medical disorder and can lead
to serious complications in certain patients such as diabetics.
• Both sexes and all age groups are affected.
• The affected patients (1) harbour a fungal reservoir and have
the potential to infect other individuals, (2) are physically and
psychologically (especially females) impaired by the diseased
nails, and (3) suffer a financial burden from repeated medical
consultations and medication costs.
• Dermatophytes, yeasts and moulds can cause onychomycosis.
Risk factors for onychomycosis
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Advanced age
Associated tinea pedis
Immunodeficiency states
Diabetes Mellitus
Peripheral vascular disease
Occlusive footwear
Sports activities
Repeated nail trauma
Impaired foot and nail hygiene
Genetic predisposition
Chronic smoking
Occupational risk (housewives, athelets)
Clinical patterns of infection
1. Distal and lateral subungual onychomycosis:
• Is the most common pattern.
• The distal parts of the nail plate to turn yellow,
brown or black, usually close to the lateral nail
fold.
• Subungual hyperkeratosis and onycholysis.
• The infection can progress proximally forming
linear channels which are highly characteristic
of onychomycosis.
• Typically caused by T. rubrum.
2. Superficial white onychomycosis:
• This less common but interesting pattern is
due to fungal invasion of the dorsal (outer)
layer of the nail plate.
• It typically presents as well-demarkated
powdery white patches or striate bands that
can easily be scraped away.
• The nail plate is often not thickened nor
elevated from the underlying nail bed.
• T. mentagrophytes var. interdigitale is the
most common pathogen.
3. Proximal subungual onychomycosis:
• Is common in AIDS patients.
• It is considered as one of the early markers of HIV
infection. The fungus gains entry to the nail
through the proximal nail fold and then extends.
• The surface remains intact.
• Transverse white patches form at the proximal
nail fold and move outwards as the nail plate
grows.
• The nail plate is marginally thickened and
onycholysis may develop.
• The main agents associated are T. rubrum and
less commonly C. albicans.
4. Endonyx:
• Here the fungus invades the entire thickness
of the nail plate.
• The nail bed is spared.
• Milky-white patches together with scarring,
coarse pitting and lamellar peeling.
• Nail thickening, separation and inflammatory
changes are not seen.
• Mainly caused by T. soudanense, T. violaceum
and T. tonsurans.
5. Total dystrophic onychomycosis (TDO):
• Two subtypes of TDO are identified:
A. The first occurs in the setting of chronic
mucocutaneous candidosis.
B. The second TDO represents the end result of
any kind of longstanding untreated
onychomycosis.
• There is almost complete destruction of the
nail plate.
Candidal Onychomycosis
Four patterns of candidal onychomycosis have been identified
1. Candidal paronychia with secondary nail dystrophy
2. Distal nail infection
3. Chronic mucocutaneous candidosis
4. Secondary candidiasis
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There are two major types of paronychia
1. Acute paronychia which is mostly caused by bacteria.
2. Chronic paronychia which is often associated with Candida.
• Chronic paronychia occurs in individuals excessively exposed to moisture
and detergents.
• Typically, many or all fingernails are affected at the same time.
• The nail folds become inflamed and the cuticle detaches from the nail
plate losing its water-proof properties.
• Yeasts get entry into the sub-cuticular area causing more inflammation
and more cuticular detachment.
• Once the nail matrix is involved, horizontal ridges (Beau's lines) appear
and the nail plate becomes irregular, thickened, and convex, and if
untreated nail dystrophy may be the end result.
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Diagnosis
• Because many other nail ailments can mimic
onychomycosis and due to the costly and
potentially harmful oral medications, it is
crucial to obtain mycological confirmation
before commencing therapy.
• KOH microscopy (bright-field illumination and
calcofluor white)
• Culture?
• Histopathology?
Treatment
• Current medications are often ineffective in the long-term
management and are often associated with high relapse? and reinfection? rates (recurrence=40%-70%). Prognosis?
• Patient compliance is critical to achieving therapeutic success.
• Terbinafine is the single most efficacious and cost-effective agent at
a single 250 mg daily dose for 3 months.
• Itraconazole and fluconazole are more effective than terbinafine
against Candida.
• Oral antifungals may not be suitable for certain patients?
• Topical antifungals (amorolfine 5% and cicolpirox olamine 8%) are
only effective for treating early and mild disease.
• Combination therapy is the best approach.
• Topical agents should also be used as a long-term prophylaxis to
prevent recurrence after successful oral therapy.
• Ketoconazole and griseofulvin?
• Nail removal.
Candidiasis
• The yeastlike fungus C. albicans and a few other
Candida species are capable of producing skin,
mucous membrane, and internal infections.
• It is part of the normal flora of the mouth, vaginal
tract, and gut.
• The yeast may become pathogenic in certain
circumstances like?
• Candidal pseudohyphae and hyphae can be
indistinguishable from dermatophytes in KOH
exam..
• Culture results must be interpreted carefully.
Why?
• The yeast infects only the outer layers of
the epithelium of mucous membranes and
skin.
• The primary lesion is a pustule, the
contents of which dissect horizontally
under the stratum corneum and peel it
away.
• The infection is confined to the mucous
membranes and intertriginous areas. Why?
Candidiasis of large skin folds
• Candidiasis of large skin folds (Candida
intertrigo) occurs under pendulous breasts,
between overhanging abdominal folds, in the
groin and rectal area, and in the axillae.
• Skin folds (intertriginous areas where skin
touches skin) contain heat and moisture.
• There are two clinical presentations:
1.macerated pustules that extend beyond the
skin fold borders; and 2.red moist glistening
plaque.
• Rx?
Diaper Candidiasis
• An artificial intertriginous area is created under a wet
diaper, predisposing the area to a yeast infection with
the characteristic red base and satellite pustules.
Rx:
• Dryness should be maintained. How?
• Antifungal creams twice a day for approximately 10
days.
• Residual erythema from irritation may be present after
10 days. What to do?
• Mupirocin ointment 2% is effective for severe Candida
and bacterial diaper dermatitis.
DDx:
Candidiasis of small skin folds
1. FINGER AND TOE WEBS
• Web spaces are like small intertriginous areas.
• Those who work in a moist environment are at
risk.
• It may coexist with dermatophytes and gramnegative bacteria.
• Clinically and in potassium hydroxide
preparations, infection by Candida and
dermatophytes may appear to be identical.
2. ANGLES OF THE MOUTH
• Angular cheilitis (inflammation at the angles of the mouth) can occur at
any age.
• Yeasts and/or bacteria may be involved in the process.
• Continued irritation by the presence of saliva at the mouth angles leads to
eczematous inflammation.
• Lip licking, biting the corners of the mouth, or thumb sucking causes
cheilitis in the young.
• In older patients: advancing age, mouth breathing secondary to nasal
congestion, malocclusion resulting from poorly fitting dentures,
compulsive lip licking and aggressive use of dental floss may cause
mechanical trauma to mouth angles.
• The infection starts as a sore fissure in the depth of the skin fold.
Erythema, scale, and crust form at the sides of the fold.
Rx:
• Antifungal creams, followed in a few hours by a group V steroid creams
until the area is dry and free of inflammation.
• Thereafter, a thick, protective lip balm is applied frequently.
• Mupirocin ointment or cream 2%.
• Cosmetic fillers injected at the mouth angles.
Tinea Versicolor
• Tinea versicolor is a common fungal infection of the
skin caused by the dimorphic lipophilic yeasts
Pityrosporum orbiculare (round form) and
Pityrosporum ovale (oval form).
• The organism is part of the normal skin flora and is
concentrated in areas with (and years of) increased
sebaceous activity.
• It resides within the stratum corneum and hair follicles.
• Certain predisposing endogenous factors or exogenous
factors?
• Some individuals, especially those with oily skin, may
be more susceptible.
• Is it contagious? Not known.
Clinically
• Lesions begin as multiple small, circular macules of
various colors (pink, white, or brown) that enlarge
radially.
• A spectrum of clinical presentations and colors:
1. Red to fawn-colored macules, patches, or follicular
papules
2. Hypopigmented lesions.
3. Tan to dark brown macules and patches.
• However, the color is uniform in each individual.
• Distribution?
• Symptoms
• DDx: Vitiligo, pityriasis alba, seborrheic dermatitis,
secondary syphilis, and pityriasis rosea.
Investigations
• Scraping & KOH: spaghetti-and-meatballs
pattern.
• Wood’s light examination shows irregular,
pale, yellow-to-white fluorescence.
Treatment
• Topical treatment is indicated for limited
disease & recurrence rates are high.
• Ketoconazole shampoo 2%.
• Selenium sulfide suspension 2.5%.
• Terbinafine spray 1%.
• Other topical antifungals.
• Oral itraconazole and fluconazole (extensive
disease and multiple recurrences).
• Oral terbinafine and griseofulvin? Ineffective.