What is dermatophytosis?

Definition

Dermatophytosis is a superficial fungal infection of the skin, hair, and nails caused by dermatophytes. The condition is generally classified according to the
location of the infection and is often referred to as tinea because of its
resemblance to infections caused by parasitic worms that burrow beneath the skin.

Causes

Dermatophytes are fungi that can grow and colonize on
keratinized, or nonliving, tissues of human and animal hosts. The
genera of fungi that most commonly cause dermatophytosis are
Microsporum, Epidermophyton, and
Trichophyton. These fungi usually remain on the outer layer of
the skin in healthy people and generate metabolic by-products that trigger an
allergic and inflammatory response.

Risk Factors

Dermatophytosis can occur in healthy persons who come in direct or indirect
contact with dermatophytes. Exposure to common transmission routes, such as shower
stalls containing the species that causes athlete’s foot, can increase the risk of
infection. Preexisting injury to the skin, such as scars,
burns, and excessive temperature and humidity, also can increase susceptibility to
infection. Immunocompromised persons, such those with human immunodeficiency virus
(HIV) infection or with acquired immunodeficiency syndrome (AIDS); persons with
chronic disease; and persons who are sick or elderly are at increased risk of
severe, subcutaneous, chronic, and recurrent dermatophytosis.

Symptoms

The symptoms of dermatophytosis vary according to the type of fungus involved and the location of the infection. The different types of dermatophytosis include tinea barbae (ringworm of the beard), tinea capitis (blackdot ringworm, or ringworm of the scalp and hair), tinea corporis (ringworm of the body), tinea cruris (jock itch, or ringworm of the groin), tinea pedis (ringworm of the foot, or athlete’s foot), tinea manuum (ringworm of the hands), and tinea unguium (ringworm of the nail). All cause inflammation that can be mild to severe, and many cause varying degrees of itchiness.

The common symptoms of athlete’s foot, for example, include
cracked, flaking, and peeling skin between the toes; red and sometimes blistering,
oozing, or crusting skin; and itching, burning, or stinging sensations. Athlete’s
foot can also affect the toe nails, causing them to become discolored, thick, and
crumbly.

Screening and Diagnosis

The diagnosis of dermatophytosis is made by the presence of fungi in skin, nail, and scalp scrapings seen under microscopy or by the isolation of fungi in culture. Information obtained during the patient history and physical examination, such as the appearance of the lesion, travel history, animal contacts, and race, are also helpful in diagnosing dermatophytosis.

Treatment and Therapy

The treatment of dermatophytosis varies according to the type of infection.
Both topical and systemic antifungal agents are used. Antibiotics
may also occasionally be necessary to treat secondary bacterial
infections that occur as a result of scratching. In the case
of tinea capitis, treatment often includes oral antifungal agents such as
griseofulvin, terbinafine, and itraconazole, and a medicated shampoo to reduce the
spread of infection.

Prevention and Outcomes

Dermatophytosis can be transmitted by direct contact with infected people and animals and by indirect contact with organisms on exfoliated skin or hair found in the environment. Reducing or eliminating exposure to infected hosts and contaminated objects, such as combs, shoes, and locker room floors, can help prevent dermatophytosis. Prompt treatment can also help prevent the spread of the organisms to other parts of the body and to other people.

Bibliography

Berger, T. G. “Dermatologic Disorders.” In Current Medical Diagnosis and Treatment 2011, edited by Stephen J. McPhee and Maxine A. Papadakis. 50th ed. New York: McGraw-Hill Medical, 2011.

Burns, Tony, et al., eds. Rook’s Textbook of Dermatology. 8th ed. 4 vols. Hoboken, N.J.: Wiley-Blackwell, 2010.

Wolff, Klaus, and Richard Allen Johnson. Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology. 6th ed. New York: McGraw-Hill Medical, 2009.