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Cutaneous fungal infections are categorized as follows:
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1. Superficial: infecting the stratum corneum, hair,
and nails.
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- The three major genera are Trichophyton, Microsporum,
and Epidermophyton. The term “tinea” is used to
denote fungal infection and is typically modified by site (e.g.,
tinea capitis, tinea corporis).
- Candida is a normal inhabitant of the oropharynx and gastrointestinal
tract. Moist, wet conditions favor Candida overgrowth and can lead
to superficial infection of the skin.
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2. Deep: involving the dermis and subcutaneous tissues.
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- Subcutaneous mycoses are the result of implantation and
include chromoblastomycoses, mycetoma, sporotrichosis, basidiobolomycosis,
and lobomycosis.
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Deep mycoses are the result of hematogenous spread or extension
from an underlying structure. True pathogens infect hosts with normal
immunity and include histoplasmosis, coccidioidomycosis, and paracoccidioidomycosis.
Opportunistic pathogens infect immunocompromised hosts and include
disseminated candidiasis and aspergillosis.
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Tinea capitis is a fungal infection (Microsporum or Trichophyton)
of the scalp and hair characterized by follicular inflammation with
painful, boggy nodules that drain pus and result in hair loss.
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If there is any doubt about the diagnosis, a fungal culture of
affected hairs and scale can be very helpful. If systemic treatment
is given without improvement, the initial diagnosis is called into question,
but culture after treatment is extremely low-yield.
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Age Children: 2 to 10 years; rarely
seen in infants or adults.
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Incidence Most common fungal infection
in childhood. Eight percent of the pediatric population.
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Etiology Trichophyton tonsurans
(90%) in the United States and West Europe. > Microsporum
canis > M. audouinii > T. verrucosum. T. violaceum > T. tonsurans
in Southeast Europe and North Africa.
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Two to four days after exposure, scaly pruritic patches appear
in the scalp with hair loss. Untreated, the lesions enlarge. Systemic
symptoms may include cervical lymphadenopathy, malaise, or fever.
Additionally, a systemic allergy to fungal elements can be seen
(see “Tinea and Id Reaction”).
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1. Ectothrix (infection on the outside of the hair
shaft).
a. Gray patch ringworm. Brittle hair; shafts break off close
to scalp surface. Caused by M. audouinii and M. canis (Fig. 21-1).
2. Endothrix (infection on the inside of the hair shaft).
a. Black dot ringworm. Broken-off hairs give appearance of black
dots, caused by T. tonsurans and T. violaceum (Fig. 21-2).
b. Kerion. Boggy, purulent, inflamed painful nodule drains pus.
Hairs do not break but fall out easily. Heals with residual hair
loss (Fig. 21-3).
c. Favus. Scutula (yellowish crusts) are present on the scalp
infected with ...