Transcript Document 7293072

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FUNGAL
SKIN
INFECTIONS
I
IHAB YOUNIS, M.D.
• At one time it was thought that fungi were
plants that did not need photosynthesis
• But now fungi are classified in their own
kingdom, separate from plants and animals
because:
1- The cell walls of plants are made of
cellulose whereas the walls of fungal cells
are made of chitin
2- Plants require only simple inorganic
compounds such as carbon dioxide and water
to grow. Fungi require a diet of complex
organic molecules to thrive
• Fungi may be broadly divided into two
basic forms, moulds and yeasts
– Moulds are made up of long
multinucleate filaments called
hyphae
– Yeasts are unicellular, made up of ovoid to
globose cells which usually reproduce by
budding
• Dermatophytes are fungi that can cause
infections of the skin, hair, and nails
• They colonize the keratin and inflammation
is caused by host response to metabolic byproducts
• The organisms are transmitted by either
direct contact with infected host
(human or animal) or by direct or
indirect contact with infected exfoliated
skin or hair in combs, hair brushes,
clothing, furniture, theatre seats, caps,
bed linens, towels, hotel rugs, and
locker room floors
• Depending on the species, the organism
may be viable in the environment for up
to 15 months
Classification of dermophytes
according to habitat
• Anthropophilic dermatophytes are restricted to
human hosts and produce a mild, chronic
inflammation
• Zoophilic organisms are found primarily in
animals and cause marked inflammatory
reactions in humans who have contact with
infected cats, dogs, cattle, horses, birds, or
other animals.
• Geophilic species are usually recovered from
the soil but occasionally infect humans and
animals. They cause a marked inflammatory
reaction, which limits the spread of the infection
and may lead to a spontaneous cure but may
also leave scars
The main 3 genera of dermatophytes are:
• Trichophyton
• Epidermophyton
• Microsporum
Classification of fungal
skin diseases
A .Superficial mycoses
Infections limited to the outermost
layers of the skin and hair:
– Pityriasis versicolor
– Candidiasis
– Tinea nigra
– Black piedra
– White piedra
B .Cutaneous mycoses
• Infections that extend deeper into the
epidermis, as well as hair and nail and
caused by dermatophytes:
– Tinea
– Tinea
– Tinea
– Tinea
– Tinea
– Tinea
capitis
corporis
manus
cruris
pedis
unguium
C .Subcutaneous mycoses
Infections involving the dermis,
subcutaneous tissues, muscle & fascia :
– Sporotrichosis
– Chromoblastomycosis
– Mycetoma
D. Systemic mycoses
• Infections that originate primarily in the
lung and may spread to many organs
Tinea Versicolor
Etiology
• Malassezia furfur (Syn. Pityrosporon
orbiculare, Pityrosporon ovale, and
Malassezia ovalis)
• A member of normal human cutaneous
flora, and it is found in 18% of infants
and 90-100% of adults
• The condition is more noticeable during
the summer months
• In patients with clinical disease, the
organism is found in both the yeast
(spore) stage and the filamentous
(hyphal) form
• Factors that lead to the conversion to
the parasitic, mycelial morphologic form
include a genetic predisposition; warm,
humid environments; immunosuppression; malnutrition; and Cushing
disease
• Prevalences reported to be as high as 50%
in the humid, hot environment and as low
as 1.1% in the colder temperatures
• The condition is not considered to be
contagious because the causative fungal
pathogen is a normal inhabitant of the skin
• Its occurrence before puberty or after age
65 years is uncommon
• The reason why this organism causes
tinea versicolor in some individuals
while remains as normal flora in others
is not entirely known
• Several factors, such as the organism's
nutritional requirements and the host's
immune response to the organism, are
significant
• Evidence has been accumulating to
suggest that amino acids (rather than
lipids as previously thought) are critical
for the appearance of the diseased
state
• In vitro, the amino acid asparagine
stimulates the growth of the organism,
while glycine induces hyphal formation
• In vivo, the amino acid levels have been
shown to be increased in the uninvolved
skin of patients with tinea versicolor
• Lymphocyte function on stimulation
with the organism has been shown to
be impaired in patients who are
affected
Clinically
• Numerous, well-marginated, finely
scaly, oval-to-round macules
• Scattered over the trunk and/or the
chest, with occasional extension to the
lower part of
the abdomen,
the neck, and
the proximal
extremities
• The macules tend to coalesce, forming
irregularly shaped patches
• As the name versicolor implies, the
color of each lesion varies from almost
white to reddish brown or fawn colored
• An inverse form also exists affecting the
flexural regions, the face, or isolated
areas of the extremities
• This form is more often seen in hosts
who are immunocompromised
Cutaneous Candidiasis
Etymology : Latin,
feminine of
candidus=Clear
Etiology
• Candida albicans yeasts are unicellular
fungi that typically reproduce by
budding, a process that entails pinching
off of the mother cell
• It has the ability to exist in both hyphal
and yeast forms (dimorphism)
• If pinched cells do not separate, a chain
of cells is produced and is termed
pseudohyphae
• Candidal species are part of the normal
commensal flora throughout the
gastrointestinal tract (mouth through
anus)
• The vagina also is commonly colonized
by yeast (13% of women), most
commonly by C albicans
• Removal of bacteria from the skin, vagina
and gastrointestinal tract results in
reduced environmental and nutritional
competition that favors the growth of
candidal organisms
Incidence increased due to:
• Postnatal acquisition has been
attributed to increased survival rates of
low birth weight babies in association
with an increased number of invasive
procedures
• Older adults are more likely to be
exposed to situations that increase the
risk of invasive candidiasis, including
treatment with broad-spectrum
antibiotics , poor self-care, and
decreased salivary flow
• The use of broad spectrum antibiotics,
and treatment with cytotoxic agents
(eg, methotrexate, cyclophosphamide)
for dermatologic and rheumatic
conditions or aggressive chemotherapy
for malignancy
Clinical Types
Candidal vulvovaginitis
• This common condition in women presents
with itching, soreness, and a thick creamy
white discharge
• Although most candidal infections occur more
frequently with advancing age, vulvovaginitis
is unusual in older women. In the absence of
estrogen stimulation, the vaginal mucosa
becomes thin and atrophic, producing less
glycogen. Candidal colonization of vaginal
mucosa is estrogen dependent and
subsequently decreases sharply after
menopause
• Erythema of vaginal mucosa and vulval skin
• Curdy white flecks within the discharge
• Erythema may spread to include the
perineum&groin
with satellite
pustules
• Alternatively, the
vaginal mucosa
may appear
red and glazed
Candidal balanitis
• Signs and symptoms of this candidal
infection vary but may include tiny
papules, pustules, vesicles, or persistent
ulcerations on the glans penis
• Exacerbations following intercourse are
common
Oropharyngeal candidiasis (oral thrush)
• Acquired from the infected maternal mucosa
during passage of the infant through the birth
canal
• Lesions become visible as pearly white patches
• Buccal epithelium, gums, and the palate are
involved with extension to the tongue, pharynx,or
esophagus in more severe cases
• If the lesions are scraped away, an erythematous
base is exposed. Lesions may progress to
symptomatic erosion and ulceration
Oral candidiasis in adults
• In older adults, the development of oral
thrush in the absence of a known
etiology should raise the clinician's
index of suspicion for an underlying
cause of immunosuppression, such as
malignancy or AIDS
• With denture stomatitis, the areas of
erythema may be painful and may
affect up to 65% of patients who wear
dentures
• Occurs as white plaques
that are present on the
buccal, palatal, or
oropharyngeal mucosa
overlying
areas of
mucosal
erythema
•Typically, the lesions are
easily removed & may show
areas with tiny ulcers
• In addition, some patients may develop
soreness and cracks at the lateral angles
of the mouth (angular cheilitis)
• Denture stomatitis presents as chronic
mucosal erythema typically beneath the
site of a denture
Candidal diaper dermatitis
• 85-90% of infants with OPC harbor C
albicans in the intestine and feces and
in most patients, CCD is the result of
progressive colonization from oral and
gastrointestinal candidiasis
Factors predisposing to infection:
-Infected stools
-Macerated moist skin
-Local irritation of the skin by friction
-Ammonia from bacterial breakdown of
urea
-Intestinal enzymes
-Detergents and disinfectants
• Maceration of
the anal mucosa
and the perianal
skin often is the
first clinical
manifestation
• Usually it starts in
the perianal area,
spreading to involve the perineum and, in severe
cases, the upper thighs, lower abdomen, and
lower back
• The typical eruption begins
with scaly papules that
merge to form well-defined,
weeping, eroded lesions
with a scalloped border
• A collar of overhanging
scales and an erythematous
base may be demonstrated
• Satellite flaccid vesicopustules around the primary
intertriginous plaque also
are characteristic
Intertrigo
• Most cases occur in skin folds where
occlusion (by clothing or shoes)
produces abnormally moist conditions
• Other sites include the perineum,
mouth, and anus, in which Candida
organisms normally may be carried
• Candidal infection of the skin under the
breasts occurs when those areas
become macerated
• Erythema, cracking, and maceration with
soreness and pruritic symptoms
• Lesions typically have an irregular margin
with surrounding satellite papules and
pustules
• Web spaces of affected
fingers or toes are
macerated and have
the appearance of soft
white skin, which is a
condition termed
erosio interdigitalis blastomycetica
Paronychia
• Candida species (not always C albicans)
can be isolated from most patients
• Bacteria also may act as copathogens
• Immediate contact dermatitis to food
allergens may play a role
• Disease is more common in people who
frequently submerge their hands in
water and in diabetics
• The nailfold becomes erythematous,
swollen, and tender, with an occasional
discharge
• Loss of the cuticle occurs, along with
nail dystrophy and onycholysis with
discoloration around the lateral nailfold
• A greenish color with hyponychial fluid accumulation
may occur that results
entirely from Candida,
and not Pseudomonas infection
Chronic Mucocutaneous Candidiasis
• CMC is associated with a defect in cellmediated immunity
• The alterations include decreased IL 2 and
interferon-gamma levels & increased IL 10
• Usually manifests in infancy or early
childhood (60-80% of cases)
Clinically
• Infants often present with recalcitrant
thrush, candidal diaper dermatitis, or both
• More extensive scaling of skin lesions and
thickened nails and red, swollen periungual
tissues can follow these infections
• Oral involvement may extend to the
esophagus, but further extension is
extremely uncommon
• Nails may be markedly thickened,
fragmented, and discolored, with
significant edema and erythema of the
surrounding periungual tissue,
simulating clubbing
• Skin lesions more frequently are acral and
characterized by erythematous,
hyperkeratotic, serpiginous plaques
• The scalp may be involved with similar
hyperkeratotic plaques,
which can result in
scarring alopecia
Tinea Nigra
Etiology
• It is due to infection by the fungus, P
werneckii
• Occurs as a result of
inoculation from a
contamination
source such as soil,
sewage, wood, or
compost subsequent
to trauma in the
affected area
Note the 2 celled yeast forms
• Tends to occur in areas with an
increased concentration of eccrine
sweat glands
• Hyperhidrosis appears to be a risk
factor for this disease
• Typically, the incubation period is 2-7
weeks
• A pigmentary change in the skin results
from the accumulation of a melanin-like
substance in the fungus
Clinically
• Asymptomatic brown-to-black macule
ranging from light brown to black
discoloration, resembling silver nitrate or
India ink stains
• The borders are typically discrete
• The surface may appear mottled or velvety
• The lesions are
typically solitary,
although may be
multiple
• Located on the
palms and soles
• The shape of the lesion varies, and they
may appear ovoid, round, or irregular
• The lesion slowly grows over weeks to
months
• The size may range
from a few
millimeters to
several centimeters in
diameter, depending
on the duration
Piedra
Etymology: Sp.Stone
Etiology
• White piedra is caused by the genus
Trichosporon Behrend which consists of
6 human pathogenic species
• Black piedra is caused by the fungus
Piedraia hortae
• Present in the soil, air,
water, vegetables,
or sputum
Clinically
• Black piedra
– Consists of darkly pigmented, firmly
attached nodules that vary in size to as
large as a few
millimeters in
diameter
– The nodules feel
hard
– The most commonly affected area of the
body is the scalp hair. Black piedra less
frequently affects beards, mustaches, and
the pubic hair
– The fungus grows into the hair shaft;
ultimately, it may cause hair breakage
because of structural instability
White piedra
– Consists of lightly pigmented, loosely
attached nodules or gelatinous
sheaths that have a soft texture
– The most commonly affected areas of
the body are
beards, pubic &
axillary hair,
mustaches and
eyelashes and
eyebrows
– Hair breakage occurs in both forms
– In both varieties of piedra, the
surrounding skin is healthy