Differentiating the Types of Tinea

Tinea is caused by dermatophytes that can infect the stratum corneum epidermidis, hair, and nails. Dermatophytosis is a common infection worldwide, and about 20% of the US population is infected.¹ Although numerous fungi can cause tinea, Trichophyton, Microsporum, and Epidermophyton are the genera that cause most cases of tinea.² Classified by the part of the anatomy that is infected, tinea is referred to as tinea pedis, tinea manuum, tinea cruris, tinea corporis, tinea capitis, tinea faciei, tinea barbae, and tinea unguium.

Tinea pedis
Otherwise known as athlete's foot, tinea pedis is among the most common fungal infections and is the second most common skin disease in the United States.³ Up to 15% of the US population has tinea pedis.^4,5

There are 3 types of tinea pedis: vesicular, moccasin, and interdigital. The vesicular type generally affects the sole of the foot and is characterized by the acute onset of vesicles or bullae (Figure 1). The moccasin type typically affects the lateral aspects and soles of the feet and is characterized by diffuse erythema and scaling (Figure 2). The interspace and underside of the toes are usually involved in the interdigital type; maceration between the toes, which can lead to painful fissures, is often present (Figure 3).

Figure 1 -

This case of vesicular tinea pedis was initially misdiagnosed as dyshidrotic

eczema. (Photograph courtesy of Dr Charles E. Crutchfield III. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:221.)

Figure 2 -

This patient with long-standing moccasin-type tinea pedis had been applying

over-the-counter 1% hydrocortisone ointment to his occasionally itchy feet for decades. After a heat wave, he finally sought care because the eruption became highly pruritic. (Photograph courtesy of Joe Monroe, PA-C. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:218.)

Figure 3 -

As seen in this patient with interdigitaltype tinea pedis, the interspace and underside of the toes are generally involved, and maceration between the toes is usually present. (Photograph courtesy of Dr Charles A. Woods. From Double Take. Superficial pediatric skin infections. Consultant. 1998;38:1807.)

The 3 species of fungi that cause most cases of tinea pedis are Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum. T rubrum is the pathogen most commonly associated with chronic infections and accounts for more than 67% of all cases of tinea pedis.³

Tinea manuum
This infection tends to occur in patients with concurrent tinea pedis. Tinea manuum involves the hands and is characterized by fairly well-demarcated erythema and scaling of the palms (Figure 4). When both the hands and the feet are involved, either both hands and 1 foot or 1 hand and both feet are affected.² The reason for this phenomenon is unknown.

Figure 4 -

The scaling on the palm of this hand was caused by tinea manuum. (Photograph courtesy of Dr Robert P. Blereau. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:222.)

Tinea cruris
Also referred to as "jock itch," tinea cruris involves the groin and affects men more frequently than women. This infection tends to occur more often during warmer months and is associated with increased sweating. T rubrum, T mentagrophytes, or E floccosum generally causes this infection, which typically presents as fairly well-demarcated, pruritic plaques with a raised active border over the inner thigh (Figure 5). The scrotum usually is not involved.

Figure 5 -

This asymmetric, maculopapular, sharply demarcated, pruritic, excoriated dermatitis was caused by tinea cruris. (Photograph courtesy of Dr Robert P. Blereau. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:225.)

Tinea corporis
Circular lesions that can erupt anywhere on the trunk and extremities characterize this infection. The lesions usually appear as annular plaques with central clearing and an active scaly border (Figure 6). An inflammatory type of tinea corporis can also occur; this type involves elevated boggy plaques and may involve follicular pustules. T rubrum is usually the cause of both types of tinea corporis.

Figure 6 -

Despite a negative finding for fungi on a culture of material from this lesion, tinea corporis was diagnosed. The eruption cleared completely after a 4-week course of econazole cream applied twice daily. The negative fungal culture result may have occurred because the specimen was taken from an area with little crusting. (Photograph courtesy of Dr Robert P. Blereau. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:226.)

Tinea capitis
This scalp infection usually occurs in children and is rarelyseen in adults. Tinea capitis is relatively contagious, and the causal dermatophyte, most commonly Trichophyton tonsurans, can be spread by shared items, such as hats, brushes, and combs. Patients who have tinea capitis generally present with patches of hair loss, scaling of the scalp, and sometimes kerions (Figure 7).

Figure 7 -

Tinea capitis was diagnosed in this 3-year-old girl after a potassium hydroxide preparation of scrapings that contained hairs from the affected area was positive for the "endothrix" phenomenon- the finding of fungal elements inside the hair shaft. (Photograph courtesy of Joe Monroe, PA-C. From Photo Essay. Tinea types: common dermatophyte infections. Consultant. 2004;44:229.)

If "black dot" tinea capitis is present, then only tiny dark spots on affected areas of the patient's scalp will be visible. This occurs because the dermatophyte within the hair shaft causes the hair to become brittle and break off at the level of the scalp.

Tinea faciei
Limited to the glabrous skin of the face, tinea faciei can be difficult to diagnose. Because of this, tinea faciei is sometimes called "tinea incognito." Signs of this infection are annular or serpiginous erythematous, scaly plaques with an active border composed of papules, vesicles,or crusts (Figure 8). The most common location is the cheeks; some patients have multiple lesions in different areas of the face.

Tinea barbae
This infection involves the chin, neck, and maxillary and submaxillary regions of the face and affects only men (Figure 9). Usually, the outbreak is unilateral and the upper lip is spared. Tinea barbae is caused most often by T mentagrophytes and Trichophyton verrucosum; occasionally, it is caused by Microsporum canis.

Tinea unguium
Also called onychomycosis, or infection of the nails, tinea unguium affects up to 20% of persons in the United States and accounts for 50% of all nail disease.⁶ Toenails are involved more often than fingernails and are more difficult to treat. The infection is more common in adults than in children.

Patients at greatest risk for onychomycosis are those with diabetes, peripheral vascular disease, or HIV infection; patients older than 60 years are susceptible as well. Local nail trauma, psoriasis, and tinea pedis also increase the risk of tinea unguium.

The dermatophytes T rubrum and T mentagrophytes cause up to 90% of these infections.⁶ The remainder are caused by yeasts (primarily Candida albicans) or other molds (usually Scopulariopsis brevicaulis).

Onychomycosis is often divided into 4 categories: superficial, proximal subungual, distal subungual, and total dystrophic. Superficial onychomycosis is typically easier to manage and more responsive to topical therapy; the surface of the nail plate ispowdery white, and only the toenails are affected. Proximal subungual onychomycosis is more common in HIVpositive patients and more difficult to culture; the nail plate remains intact, and transverse white bands develop. Distal subungual disease is the most common form; the nail plates are yellowish and thickened with subungual hyperkeratosis and often separate from the nail bed. Total dystrophic onychomycosis affects the entire nail and behaves like a combination of all other types (Figure 10).

Diagnosis and treatment
The most common method used to diagnose tinea is the appearance of the skin and a potassium hydroxide (KOH) examination. Direct microscopy of a KOH preparation of scale scraped from a lesion generally will reveal fungal elements. Skin culture and skin lesion biopsy are rarely required. A dermatophyte culture may be appropriate when a fungal infection is strongly suspected but a KOH examination result is negative. Unfortunately, these cultures can take up to 6 weeks to become positive. Histopathological examination using periodic acid-Schiff stain may also be helpful in identifying fungi within material from a skin biopsy or nail clippings.²

Patients with tinea pedis should keep their feet clean and dry at all times. Application of a topical antifungal medication, such as ketoconazole, terbinafine, econazole, or cicloprox, for 4 weeks is usually an effective treatment for tinea cruris, tinea corporis, tinea pedis, and tinea manuum.² Antifungal powders may be more useful for the interdigital type of tinea pedis, and lotions are preferable for use on hair-bearing areas.

Tinea capitis, extensive tinea corporis, and tinea unguium are best treated with systemic medications, such as griseofulvin, itraconazole, fluconazole, and terbinafine.² Patients with tinea unguium who have been treated successfully with systemic antifungal agents are often given topical antifungal medications to prevent recurrences.

References:

• Vander Straten MR, Hossain MA, Ghannoum MA. Cutaneous infections dermatophytosis, onychomycosis, and tinea versicolor. Infect Dis Clin North Am. 2003;17:87-112.
• Grin C. Tinea: diagnostic clues, treatment keys. Consultant. 2004;44:214-216.
• Weinstein A, Berman B. Topical treatment of common superficial tinea infections. Am Fam Physician. 2002;65:2095-2102.
• Bell-Syer SE, Hart R, Crawford F, et al. Oral treatments for fungal infections of the skin of the foot. Cochrane Database Syst Rev. 2002;(2):CD003584.
• Patel A, Brookman SD, Bullen MU, et al. Topical treatment of interdigital tinea pedis: terbinafine compared with clotrimazole. Australas J Dermatol. 1999;40:197-200.
• Conger NG, Hospenthal DR. Current therapy for onychomycosis. Infect Med. 2005;22:280-283.