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Dermatophytoses

Introduction
Dermatophytoses are fungal infections caused by three genera of fungi that have
the ability to invade and multiply within keratinized tissue (hair, skin and
nails):include
(1) Trichophyt on
(2) Epidermophyton
(3) Microsporum
Epidemiology
Trichophyton rubrum is the most common dermatophyte worldwide
Dermatophytoses o ccur most frequently in postpubertal hosts except tinea capitis
which occurs mainly in prepubertal children
Men tend to more frequently have tinea cruris and tinea pedis than women
Pathogenesis
The f irst step : fungus comes in contact with the skin via three source s

The second step : how the fun gus invade the skin

Clinical features
Tinea corporis
Infection of the skin of the trunk and extremities, excluding the hair, nails, palms,
soles and groin
Infection spreads centrifugally f rom the point of skin invasion resulting in a raised,
erythematous, scaly advancing border and a central clearance (annular or circinate
lesion)
Variants:
Tinea incognito: tinea lesion modified by topical steroids, may lack a raised scaly
active border .

Tinea cruris (Jock itch)

Infection of the inguinal region
This disease is more often seen in men than in women, since the scrotum provides
a warm and moist environment that encourages fungal growth
The inflicted patients are more likely to have tinea pedis and ony ch mycosis as a
source of dermatophytes (which are transmitted from these places to inguinal area)
Predisposing factors include obesity and hyperhidrosis
Presented clinically similar to tinea corporis (annular lesion)
Tinea manuum
Infection of the palm and interdigital spaces
It is different from that of back of hands due to lack of sebaceous glands on the
palms
Often unilateral
It presents as a diffuse hyperkeratosis of the palms and digits with accentuation of
scales on creases that fails to respond to emollients
An important clinical clue is tinea unguium
Is often present in patients with tinea pedis (two feet and one hand syndrome)
Tinea pedis (Athlete' s foot)
infection of the soles and int erdigital spaces of the feet
The feet are the most common location for dermatophyte infections
M ore common in adults
Lack of sebaceous glands and moist environment due to occlusive shoes are
predisposing factors
Tinea pedis is uncommon in populations that do not wear shoes although the
barefoot people can acquire the fungus in public facilities i.e. gym
Clinical t ypes:
(1)Moccasin: diffuse hyperkeratosis, scaling and erythema

(2)Interdigital : the most common type; eryt hema, maceration, fissures and

ulceration in web spaces
Tinea barbae
Involves the bearded areas of the face and neck in men
Two types:
(1) Inlammatory type: produces nodules and kerion -like boggy swellings . A cquired
from animal, caused by T. verrucosum.
(2) Non -inlammatory type: less inflammatory, characterized by folliculitis , caused
by T. rubrum. A cquired from contaminated razors in barber - shops. Now less
common owing to use of disposable instruments and use of disinfectant
In both types: the hairs ar e either easily plucked or lost.
Tinea faci ei
Infection of face
Typical annular lesions are usually lacking and the lesions are photosensitive;
therefore, Frequently misdiagnosed
Tinea capitis
A common dermatophyte infection of the scalp in children, whereas adult infection
occurs infrequently
T. tonsurans is currently the most common cause of tinea capitis in the US while
T.verrucosum in Iraq
The “carrier state” of tinea capitis is contagious to others through hats, brushes,
towels or barber instruments
There are two clinical t ypes:
(1) Non -inflammatory:
Gray patch: present as a dry scaly patch of alopecia
Black dots: caused by hair breakage near the surface
(2) Inflammatory:

Kerion: caused by M.canis, present as a boggy, purulent plaques with abscess

formation and associated alopecia, patient may become febrile with extensive
lymphadenopathy
Favus: caused by T. schoenleinii, the most severe type of dermatophyte hair
infection, present as , sulfur -yellow crusts pierced by hairs
Tinea unguium (dermatophytic onychomycosis)
Infection of the nail unit
Three clinical types:
(1)D istal/lateral subungual: most common
(2)S uperficial white:
(3)P roximal subungual: seen freque ntly in immunocompromised hosts .
Multipl e nails on one or both hands or feet are usually affected
Af fects women more often than men
Fingernail infections are cons iderably more common than toe nail
Clinical maniestation s:
(1) Hyperkeratosis of nail bed
(2) Thickeneni ng and yellowish discoloration of nail plate
(3) Onychlysis (seperation of nail plate from nail bed)
Diagnosis of dermatophytoses
Clinical examination (most important)
KOH examination of skin scraping , nail clipping or hair plucking under microscope
after adding KOH to specimen to look for hyphae
Wood’s lamp (ultraviolet light of 365 nm wavelength): Infected hairs show yellow -
green fluorescence in a dark room
Culture: 2-4 weeks
Biopsy: we see hyphae in stratum corneum
Treatment

Topical anti fungals e.g. clotrimazole and ketoconazole are the first line treatment

Systemic anti fungal: indications
(1)tinea manuum, ( 2) tinea pedis, ( 3)tinea capitis, (4) tinea barbae , (5)tinea
unguium and (6)w hen extensive area of skin is involved


رفعت المحاضرة من قبل: Mubark Wilkins
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