Tinea is caused by dermatophytes that are capable of infecting the stratum corneum of the epidermis, the hair, and the nails. Dermatophytoses are common worldwide, and it has been estimated that about 20% of Americans are infected.1
Although numerous fungal species can cause tinea, only a few of these dermatophytes are responsible for most of the infections. The culprit species belong to 3 genera: Trichophyton, Microsporum, and Epidermophyton.
Here I describe the presentations of the common tinea infections and diagnostic techniques for cutaneous fungal disease; I also discuss treatment options and prognosis. Cases that illustrate the various tinea types are provided in the Photo Essay on page 217.
Tinea is usually classified by the part of the anatomy that is infected. Thus, these conditions are referred to as tinea pedis, tinea manuum, tinea cruris, tinea corporis, tinea capitis, tinea faciei, tinea barbae, and tinea unguium. The typical presentation of each of these infections follows.
Tinea pedis. The most common fungal infection of the skin, tinea pedis-commonly referred to as "athlete's foot"-is usually caused by Trichophyton rubrum or Trichophyton mentagrophytes. Clinically, the dermatophytosis can present as:
- Diffuse erythema and scaling of the soles of the feet. The differential diagnosis of this manifestation-which is known as the "moccasin" type of tinea pedis-includes psoriasis and lichen planus.
- Maceration between the toes. Tinea of the web spaces causes maceration, which can lead to painful fissures.
- An erythematous vesicular or bullous eruption. Characterized by the acute onset of vesicles or bullae, these tinea infections must be differentiated from allergic contact dermatitis, dyshidrotic eczema, and cellulitus.
Tinea manuum. This infection involves the hands and can be seen in patients with concurrent tinea pedis. Typically, fairly well-demarcated erythema and scaling affect the palms. Often, when the hands and feet are involved, either both hands and 1 foot or 1 hand and 2 feet are affected. The explanation for this phenomenon is unknown.
Tinea cruris. Often referred to as "jock itch," tinea cruris involves the groin and affects men more frequently than women. The infection appears to be more common during the warmer months and is associated with increased sweating.
Tinea cruris can be caused by T rubrum, T mentagrophytes, or Epidermophyton floccosum. It presents as fairly well-demarcated, often pruritic plaques with a raised active border over the inner thighs; typically, the scrotum is spared. The differential diagnosis includes inverse psoriasis, seborrheic dermatitis, erythrasma, and candidiasis; however, the latter disease usually involves the scrotum. In addition, tumors such as Bowen disease and extramammary Paget disease can present with erythematous plaques in the groin; these disorders must be differentiated from tinea infections.
Tinea corporis. The typically circular lesions can erupt anywhere on the trunk and extremities. Usually, annular plaques with central clearing and an active, scaly border arise. However, a deep, inflammatory type of tinea corporis with elevated, boggy plaques and follicular pustules can occur. The differential diagnosis for the annular plaque eruption includes psoriasis, nummular eczema, and pityriasis rosea; the inflammatory form can resemble furunculosis. Tinea corporis is usually caused by T rubrum.
Tinea capitis. Trichophyton tonsurans frequently causes this scalp infection, which occurs most commonly in children and is rarely seen in adults. Relatively contagious from person to person, the culprit dermatophyte can be spread by shared items, such as hats, brushes, and combs.
Generally, tinea capitis presents with patches of hair loss, scaling and, occasionally, tender, boggy plaques called "kerions." The differential diagnosis includes alopecia areata, which can be distinguished from the fungal infection by the presence of totally hairless areas of scalp and by the absence of scale. Seborrheic dermatitis is also in the differential and usually can be differentiated from tinea capitis by diffuse scaling with insignificant hair loss.
In "black dot" tinea capitis, the dermatophyte within the hair shaft causes the hair to become brittle and break off at the level of the scalp. Only tiny dark spots are then noted on affected areas of the patient's scalp.
Tinea faciei. This fungal infection is limited to the face. The diagnosis can be difficult; therefore, this type of tinea may be referred to as "tinea incognito."
Tinea barbae. Distributed in the beard and mustache area, this condition is seen only in men. The infection is most often caused by T mentagrophytes and Trichophyton verrucosum; occasionally Microsporum canis is the culprit.
Typically, the chin, neck, and maxillary and submaxillary regions are involved. The outbreak is usually unilateral, and the upper lip generally is spared. These features distinguish tinea barbae from bacterial folliculitis, which often involves the upper lip and is bilateral.
Tinea unguium. Also called onychomycosis, this disease involves the fingernails and/or toenails. It is more common in adults than in children. Clinically, tinea infections of the nails can present as:
- Distal subungual onychomycosis. This is the most common type of tinea unguium. The nail plates are yellowish and thickened with subungual hyperkeratosis; the nail plate often separates from the nail bed.
- Proximal subungual onychomycosis. The nail plate remains intact and transverse white bands develop.
- White superficial onychomycosis. The surface of the nail plate is powdery white. This infection occurs in the toenails; it does not affect the fingernails.
Tinea unguium must be differentiated from nail psoriasis; however, the 2 conditions may coexist.