2. 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
3. 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)
4. 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
5. 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
6. 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
7. 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
8. 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
10. 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
11. 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)
12. Transmission
• Close human contact
• Sharing clothes, combs, brushes, towels,
bedsheets... (Indirect)
• Animal-to-human contact (Zoophilic)
13. 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
15. 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
16. 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
17. 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
19. 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
21. 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
24. 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
25. Tinea Manuum
Dermatophyte infection of skin of palmar aspect of hands
The most common clinical manifestation is diffuse
hyperkeratosis of palms and fingers
26. 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
28. 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
29. Wood’s lamp
In suspected Tinea capitis, plucked hair is examined by
using wood’s lamp
Infected hair will be fluorescent (yellow green)
30. 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)
31. 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
32.
33. 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
34.
35. 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
37. 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