Dermatophytosis, raghu

Dermatophytoses
Dr. Pendru Raghunath Reddy
Assistant Professor of Microbiology
Dr. VRK Women’s Medical College

Dermatophytoses or cutaneous mycoses are diseases of
the skin, hair and nail
Generally called ringworm infections and tinea
These infections are caused by a homogenous group of
closely related fungi known as dermatophytes
These dermatophytes infect only superficial keratinised
structures such as skin, hair and nail but not deeper tissues

The most important dermatophytes that cause infection in
humans are classified into three genera
Trichophyton - infections on skin, hair, and nails.
Microsporum - infections on skin and hair
(not the cause of TINEA UNGUIUM)
Epidermophyton - infections on skin and nails
(not the cause of TINEA CAPITIS)

The dermatophytes on the basis of their natural habitat and
host preferences can be classified into following groups
1. Anthropophilic species
2. Zoophilic species
3. Geophilic species

Anthropophilic
Associated with humans only
Person -to-person transmission through contaminated
objects (fallen hairs, desquamated epithelium, combs,
hat, towel etc.)
Examples: Trichophyton rubrum, Microsporum audouinii and
Epidermophyton floccosum

Zoophilic
Associated with animals
Direct transmission to humans by close contact with
domestic animals (cat and dog) and occasionally wild
animals
Examples: Trichophyton violaceum and Microsporum canis

Geophilic
These are saprophytic fungi found in soil or in dead organic
substances
They occasionally cause infection in humans and animals
Examples: Microsporum gypseum and Trichophyton ajelloi

Dermatophytes usually grow only on keratinised skin and its
appendages and do not penetrate the living tissue
In some infected persons, hypersensitivity to fungus antigen
may cause secondary eruptions such as vesicles on the finger
This reaction is known as dermatophytid (Id) reaction
This reaction occurs as a result of hypersensitivity response
to circulating fungal antigen, and these lesions do not
contain any fungal hyphae

Clinical features
The skin infections caused by dermatophytes are chronic
infections of the skin often found in the warm humid areas
of the body
Typical ringworm lesions are circular , dry, erythematous,
scaly and itchy which have an inflamed border containing
papules and vesicles surrounding a clear area of relatively
normal skin
These lesions are associated with variable degrees of scaling
and inflammation
Nails are thickened, deformed, friable, discolored,
subungual debris accumulation

Dermatophytoses clinical classification
• Infection is named according to the
anatomic location involved:
a. Tinea barbae e. Tinea pedis
(Athlete’s foot)
b. Tinea corporis f. Tinea manuum
c. Tinea capitis g. Tinea unguium
d. Tinea cruris
(Jock itch)

Transmission
• Close human contact
• Sharing clothes, combs, brushes, towels,
bedsheets... (Indirect)
• Animal-to-human contact (Zoophilic)

Tinea capitis
This is the infection of the shaft of scalp hairs and presents
as the following clinical types
a) Inflammatory – Kerion, favus
b)Non-inflammatory – Black dot, Ectothrix and Endothrix
 The infected hairs in tinea capitis appear dull and grey
 The base of hair shaft as well as hair follicles is involved
 There is breakage of hair at follicular orifice which creates
patches of alopecia with black dots of broken hairs

Ectothrix
The arthrospores appear as mosaic sheath
around hair or as chains on surface of hair
shaft
The cuticle of hair remains intact
Hyphae invade hair shafts at mid follicle
and as hair grows out of follicle, hyphae
burst out of shaft and cover hair surface
with mass of small arthrospores
Caused by T. mentagrophytes, M. canis,
M. audouinii, M. gypseum and
T. verrucosum

Endothrix
Hyphae form arthrospores within hair
shaft, which is severely weakened
Cuticle of hair is usually destroyed
The arthrospores are 3-4 µm in diameter
and are observed in chains filling inside
shortened hair stubs
Caused by T. schoenleinii, T. tonsurans
and T. violaceum
T. rubrum cause both ectothrix
as well as endothrix infections

Tinea corporis
This is disease of glabrous (non-hairy) skin of body and may
result from extension of infection from scalp, groin or beard
Characterised by erythematous scaly lesions, annular, sharply
marginated plaques with raised border which may be single,
multiple or confluent

Tinea Pedis
This is the infection of plantar aspect of foot, toes and
interdigital web spaces
It is frequently seen among individuals wearing shoes for
long hours and popularly known as Athlete’s Foot
In toe webs, scaling, fissuring, maceration and erythema may
be associated with an itching or burning sensation
Due to maceration and peeling, cracks appear which are prone
to secondary bacterial infections
When infection becomes chronic, sole becomes hyperkeratotic
and is often covered with fine scales

Tinea Barbae
Infection of beard and moustache areas of face with
invasion of coarse hairs
Also called as barber’s itch
There are erythematous patches on face which show scaling

Tinea Faciei
Dermatophytic infection of skin that occurs on non-bearded
regions of face

Tinea Cruris
Dermatophytic infection of groin
Involves perineum, scrotum and perianal area and may
spread to inner third of buttock and occasionally to thigh
The appearance of Tinea Cruris can be seen in other
intertriginous areas such as axilla and around umblicus of
obese patients

Tinea Manuum
Dermatophyte infection of skin of palmar aspect of hands
The most common clinical manifestation is diffuse
hyperkeratosis of palms and fingers

Tinea Unguium
Dermatophyte infection of nail plates and is largely a
disease of adults
It begins under leading free edge of nail plate or along
lateral nail fold and may continue until entire nail plate
and nail bed are infected
There is accumulation of subungual debris in an opaque,
chalky or yellowish thickened nail

Laboratory diagnosis
Specimens
Scrapings of the skin and nail as well as short lengths of hair
plucked from the scalp. Scrapings are taken from the edges
of ringworm lesions
Direct microscopic examination
KOH wetmount
Branching hyaline septate (non-pigmented) hyphae is
considered positive for fungi; spores may also be seen

Wood’s lamp
In suspected Tinea capitis, plucked hair is examined by
using wood’s lamp
Infected hair will be fluorescent (yellow green)

Culture
Species identification is possible only by culture examination
Sabouraud’s dextrose agar containing chloramphenicol and
cycloheximide
The plates incubated aerobically at 25-300C for upto 21 days
Identification of dermatophytes in the laboratory is by
examing the macroscopic characteristics of the fungal
colonies (rate of growth, texture, colour on the observe and
reverse)

Microscopic examination
Trichophyton
Microconidia are abundant and arranged in clusters along
the hyphae
Macroconidia are relatively scanty generally elongated,
with blunt ends and have distinctive shapes in different
species
Some species possess special hyphal characters such as
spiral hyphae, raquet mycelium and favic chandeliers

Microsporum
Microconidia are relatively scanty and not distinctive
Macroconidia, the predominant spore form, are large,
multicellular, spindle shaped structures, borne singly on
the ends of hyphae
Microsporum species infect the hair and skin but usually
not the nails

Epidermophyton
Colonies are powdery and greenish yellow
Microconidia are absent
Macroconidia are multicellular, pear-shaped and typically
arranged in clusters
Epidermophyton attacks the skin and nails but not the hair

Treatment
This is by using topical preparations (ointments or gels)
containing azoles (miconazole, clotrimazole, econazole)
or terbinafine
Oral preparations of griseofulvin, azoles (ketoconazole,
itraconazole) or terbinafine

Dermatophytosis, raghu

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Dermatophytosis, raghu