CASE #2: Dermatophytosis
Dermatophytosis, or tinea, is a fungal infection involving superficial portions of the skin, hair and nails. The infection is usually caused by one of three genera: Epidermophyton, Microsporum or Trichophyton. This relatively minor condition can be acquired from animals, humans, or soil. Variations include tinea corporis (body), tinea capitis (head), tinea pedis (feet), tinea unguium (nails), tinea cruris (groin), tinea manus (hands), tinea faciei (face) and tinea barbae (beard).7
The public — and even some medical texts — still use the term “ringworm” to describe this family of infections, but this is misleading provokes unreasonable fear among many patients. Part of this legacy of fear stems from the fact that these infections were quite common many years ago, and effective treatment simply did not exist.
Far from having anything to do with worms, dermatophytes are a group of molds that invade and feed only on keratinous tissue, skin, hair and nails. Increased warmth and moisture encourage dermatophytic infections, which are limited to the upper epidermis by host defense mechanisms and therefore distinct from the so-called deep mycoses. This group of potentially serious diseases affects the deep layers of skin, lungs and internal organs and includes such conditions as histoplasmosis, blastomycosis, coccidioidomycosis and sporotrichosis.8
As this case illustrates, topical and systemic steroids can promote tinea infection because they effectively diminish host defenses. What was missing from this patient’s workup was a definitive diagnosis, which could have been obtained with a biopsy, culture or KOH preparation to identify fungal elements. The source of this patient’s dermatophyte was not clear, but T. rubrum causes the great majority of this type of tinea corporis (also known as tinea circinata).
The active border of dermatophytic infections expands centrifugally, triggering a cell-mediated response. Among other effects, this response causes an increase in epidermal cell proliferation and resultant shedding, leaving new, uninfected cells central to the advancing border. Ultimate elimination is accomplished by the development of cell-mediated immunity, but the cell wall of the organisms slows this process, making their treatment difficult.
A deeper follicular form of tinea caused by the use of topical and/or systemic steroids is called tinea incognito, because its appearance is atypical enough to render it unrecognizable. Occasionally, under the same but prolonged circumstances, the fungal infection goes even deeper, becomes indurated, and develops pinpoint areas of pustular drainage that resemble a carbuncle. This form of fungal folliculitis, also called Majocchi granuloma, is often KOH- and culture-negative and must be diagnosed with a biopsy.4
Some individuals appear susceptible to dermatophytic infections, either because of the types of lipids their skin produces or because they are able to carry T. rubrum asymptomatically (a tendency possibly inherited autosomally).9
The differential for tinea corporis is vast, so limit it to such annular and/or scaly lesions as seborrhea, eczema, psoriasis, granuloma annulare, lichen planus, erythema annulare centrifigum, nummular eczema and tinea versicolor.
Tinea versicolor is not caused by the dermatophytes and will not necessarily respond to the same antifungal medications used for true tinea. Allylamines like terbinafine (Lamisil, Terbinex) are relatively ineffective against Malassezia furfur, the commensal yeast that causes tinea versicolor.
As mentioned, a simple KOH preparation usually distinguishes fungal from nonfungal infection. Punch biopsies are routinely stained for fungal elements. Fungal cultures are simple to obtain and can be incubated at room temperature but take up to two weeks to provide definitive results.7
There are a multitude of effective treatments for tinea corporis. Mild infections can easily be treated with a topical imidazole cream, such as oxiconazole (Oxistat), econazole (Spectazole) or ketoconazole (Feoris, Nizoral), b.i.d. until clear. Other effective topical treatment includes the allylamines terbinafine or ciclopirox (Penlac). Once treated persistently with topical steroids, tinea corporis can be severe enough to require topical and oral antifungals, including terbinafine 250 mg/day for up to one month. In rare cases, terbinafine can cause hepatotoxicity, as can griseofulvin, the most commonly used alternative.10
The patient in this case was successfully treated with oral terbinafine 250 mg daily for two weeks and twice-daily application of oxiconazole lotion. Total resolution occurred one month after treatment was initiated.
Joe Monroe, PA-C, is a physician assistant specializing in dermatology at Springer Clinic in Tulsa, Okla. The author has no relationships to disclose relating to the content of this article.
2. Dover JS. Cutaneous Medicine and Surgery: Self Assessment and Review. Philadelphia, Pa.: W.B. Saunders; 1996:104-105.
3. Menter A, Korman NJ, Elmets CA et al. “Guidelines of care for the management of psoriasis and psoriatic arthritis. Section 3. Guidelines of care for the management and treatment of psoriasis with topical therapies.” J Am Acad Dermatol. 2009;60:643-659.
4. James WD, Berger TG, Elston DM. Viral diseases. In: Andrews’ Diseases of the Skin: Clinical Dermatology. 10th ed. Philadelphia, Pa.: Saunders-Elsevier; 2006:191-201, 297.
5. Sampogna F, Tabolli S, Söderfeldt B et al. “Measuring quality of life of patients with different clinical types of psoriasis using the SF-36.” Br J Dermatol. 2006;154:844-849.
6. Callen JP, Krueger GG, Lebwohl M et al. “AAD consensus statement on psoriasis therapies.” J Am Acad Dermatol. 2003;49:897-899.
8. Aly R. Ecology and epidemiology of dermatophyte infections. J Am Acad Dermatol. 1994;31(3 Pt 2):S21-S25.
9. Jones HE. Immune response and host resistance of humans to dermatophyte infection. J Am Acad Dermatol. 1993;28(5 Pt 1):S12-S18.
10. Drake LA, Dinehart SM, Farmer ER et al. “Guidelines of care for superficial mycotic infections of the skin: tinea corporis, tinea cruris, tinea faciei, tinea manuum and tinea pedis. Guidelines/Outcomes Committee. American Academy of Dermatology.” J Am Acad Dermatol. 1996; 34(2 Pt 1):282-286.
All electronic documents accessed March 8, 2012.