Chapter 138. Tinea Corporis

A 6-year-old girl is brought to the office for a round, itchy rash on her body (Figure 138-1). It was first noted 2 weeks ago. The family cat does have some patches of hair loss. Note the concentric rings with scaling, erythema, and central sparing. UV light showed green fluorescence (Microsporum species) and the KOH is positive for branching and septate hyphae. The child was treated with a topical antifungal cream bid and the tinea resolves in 3 to 4 weeks. The family cat was taken to the veterinarian for treatment, too.

Tinea corporis is a common superficial fungal infection of the body, characterized by well-demarcated, annular lesions with central clearing, erythema, and scaling of the periphery.

Dermatophytes are the most prevalent agents causing fungal infections in the United States, with Trichophyton rubrum causing the majority of cases of tinea corporis, tinea cruris, tinea manuum, and tinea pedis.

• Excessive heat and humidity make a good environment for fungal growth.
• Dermatophytes are spread by exposure to infected animals or persons and contact with contaminated items.

Tinea corporus is caused by fungal species from any one of the following three dermatophyte genus's: Trichophyton, Microsporum, and Epidermophyton. T. rubrum is the most common causative agent of tinea corporis.

• Dermatophytes produce enzymes such as keratinase that penetrate keratinized tissue. Their hyphae invade the stratum corneum and keratin and spread centrifugally outward.

• Participation in daycare centers.
• Living in a nursing home.
• Poor personal hygiene.
• Living conditions with poor sanitation.
• Warm, humid environments.
• Conditions that cause weakening of the immune system (e.g., AIDS, cancer, organ transplantation, diabetes).

The diagnosis can be made from history, clinical presentation, culture, and direct microscopic observation of hyphae in infected tissue and hairs after KOH preparation.

Clinical Features

• Pruritus of affected area.
• Well-demarcated, annular lesions with central clearing, erythema, and scaling of the periphery. Concentric rings are highly specific (80%) for tinea infections (Figure 138-1).
• Central clearing is not always present (Figure 138-2).
• Although scale is the most prominent morphologic characteristic, some tinea infections will actually cause pustules from the inflammatory response (Figure 138-3).

Typical Distribution

Any part of the body including the face and axilla (Figures 138-1, 138-2, 138-3, 138-4).

Tinea incognito is a type of tinea infection that was previously not recognized by the physician or patient and topical steroids were used on the site. While applying the steroid, the dermatophyte continues to grow and form concentric rings (Figures 138-5 and 138-6).

Tinea corporis can cover large parts of the body as in Figures 138-7, 138-8, 138-9.

In some cases the infection may cause hyperpigmentation (Figures 138-7, 138-8, 138-9).

Laboratory Studies

• KOH preparation of skin scraping can be very useful to confirm a clinical impression or when the diagnosis is not certain. Scrape the skin with the side of a slide or scalpel, making sure to scrape the periphery and the erythematous part. Scrape hard enough to get some stratum corneum without causing significant bleeding. False negatives can occur secondary to inadequate scraping, patient using topical antifungals, or an inexperienced microscopist.
• Use KOH (plain, with dimethyl sulfoxide [DMSO], or in a fungal stain) to break up the epithelial cells more rapidly without heating (Figure 138-10). It is easy to purchase a small bottle of Swartz-Lamkins fungal stain that includes KOH, a surfactant, and blue ink. The blue ink allows the hyphae to stand out, thereby saving time and decreasing the chance of a false-negative result (Figure 138-11). If the epithelial cells are not breaking up sufficiently, use a flame under the slide for approximately 5 seconds to speed up the process.
• Skin scraping and culture—Gold standard, but more costly and may take up to 2 weeks for the culture to grow. Consider culture if the KOH is negative but tinea is still suspected, or when a microscope is not available.
• Skin biopsy sent in formalin for periodic acid-Schiff (PAS) staining when the KOH and culture remain negative but the clinical picture is consistent with a fungal infection.

• Granuloma annulare—Inflammatory, benign dermatosis of unknown cause, characterized by both dermal and annular papules (Figure 138-12) (see Chapter 173, Granuloma Annulare).
• Psoriasis—Plaque with scale on extensor surfaces and trunk. Occasionally, the plaques can have an annular appearance (Figure 138-13). Inverse psoriasis in intertriginous areas can also mimic tinea corporis (see Chapter 152, Psoriasis).
• Erythema annulare centrifugum (EAC)—Scaly red rings with normal skin in the center of the rings. The scale is trailing the erythema as the ring expands while the scale is leading in tinea corporis (Figure 138-14) (see Chapter 206, Erythema Annulare Centrifugum).
• Cutaneous larva migrans has serpiginous burrows made by the hookworm larvae, and these burrows can look annular and be confused with tinea corporis (see Chapter 144, Cutaneous Larva Migrans).
• Nummular eczema—Round coin-like red scaly plaques without central clearing (see Chapter 145, Atopic Dermatitis).
• Erythrasma—Found in the axilla and groin without an annular configuration and central clearing. Fluoresces coral red under UV lamp (see Chapter 119, Erythrasma).

• Use topical antifungal medications for tinea corporis that involves small areas of the body such as seen in Figures 138-1 and 138-2.
• Although all the topical antifungal agents may be effective, the evidence supports the greater effectiveness of the allylamines (terbinafine) over the less-expensive azoles for tinea pedis and corporis. Allylamines cure slightly more infections than azoles and are now available over the counter.1,2 SOR A
• Studies show that terbinafine 1% cream or solution applied once daily for 7 days is highly effective for tinea corporis/cruris.3,4 The 1% cream (which is available over the counter as Lamisil AF) produced a mycologic cure of 84.2% versus 23.3% with placebo. Number needed to treat (NNT) = 1.6.3 SOR A
• Oral antifungal agents should be considered for first-line therapy for tinea corporis covering large areas of the body, as seen in Figures 138-6 and 138-7. However, it is not wrong to attempt topical treatment if the size of the area infected is on the borderline. The patient with tinea incognito in Figures 138-4 and 138-5 did need oral therapy to resolve her infection. Unfortunately, the postinflammatory hyperpigmentation did not resolve well.
• One randomized controlled trial (RCT) showed that oral itraconazole 200 mg daily for 1 week is similarly effective, equally well tolerated, and at least as safe as itraconazole 100 mg for 2 weeks in the treatment of tinea corporis or cruris.5 SOR B
• In one study, patients with mycologically diagnosed tinea corporis and tinea cruris were randomly allocated to receive either 250 mg of oral terbinafine once daily or 500 mg of griseofulvin once daily for 2 weeks. The cure rates were higher for terbinafine at 6 weeks.6 SOR B
• In summary, if an oral agent is needed, the evidence is greatest for the use of:
  • Terbinafine 250 mg daily for 2 weeks.6 SOR B (Terbinafine is available as an inexpensive generic prescription on the $4 and $5 plans in the United States. It also has less drug interactions than itraconazole. For these reasons it is usually the preferred treatment when an oral agent is needed.)
  • Itraconazole 200 mg daily for 1 week.5 SOR B (More expensive with more drug interactions than terbinafine.)
  • Itraconazole 100 mg daily for 2 weeks.5 SOR B

Tinea corporis and cruris are dermatophyte infections that are particularly common in areas of excessive heat and moisture. A dry, cool environment may play a role in reducing infection. In addition, avoiding contact with farm animals and other individuals infected with tinea corporis and cruris may help in preventing infection. Preventative measures for tinea infections include practicing good personal hygiene; keeping the skin dry and cool at all times; and avoiding sharing towels, clothing, or hair accessories with infected individuals.7

In individuals involved in contact sports such as wrestling, a comprehensive skin disease prevention protocol includes some combination of the following: washing of wrestling mats before and after each practice and competition; showers before and after each practice; use of clean clothing before each practice; and exclusion of infected athletes.8

Keep the skin clean and dry. Infected pets should be treated.

Consider follow-up appointments in 4 to 6 weeks for difficult and more widespread cases. If there are concerns about bacterial superinfection, follow-up should be sooner.

Patient Resources

• VisualDxHealth. Ringworm—http://www.visualdxhealth.com/adult/tineaCorporis.htm.
• Medline Plus Medical Encyclopedia—http://www.nlm.nih.gov/medlineplus/ency/article/000877.htm.

Provider Resources

• eMedicine topic—http://www.emedicine.com/DERM/topic421.htm.
• Doctor Fungus Web site—http://www.doctorfungus.org/.
• Swartz-Lamkins fungal stain can be easily purchased online at: http://www.delasco.com/pcat/1/Chemicals/Swartz_Lamkins/dlmis023/.