Tinea cruris, a dermatophytosis infection of the anogenital skin, represents "ringworm." Also called "jock itch," this is a disease much more common in men than in women. Primarily caused by Epidermophyton floccosum, Trichophyton rubrum, and Trichophyton mentagrophytes, tinea cruris often represents infection that has spread from the great toe nails (onychomycosis) or the feet (tinea pedis), also infections that are much more common in men. Obesity also predisposes to tinea cruris (52).
The predominant symptom of tinea cruris is that of itching. The rash occurs primarily on proximal, medial thighs, sometimes extending to the crural crease and hair-bearing labia majora. Because dermatophytes infect the stratum corneum of clinically hair-bearing skin, the modified mucous membranes are spared and the vagina is never affected. Classically, tinea cruris presents as well-demarcated, red, scaling plaques of the proximal, medial thighs, with the borders exhibiting more marked scale. Often, there is central clearing, and the infection progresses peripherally (Fig. 19). Sometimes, fungal organisms track down hair follicles, producing fungal folliculitis manifested by palpable red papules within the plaque. This is most marked in women with coarse terminal hair and this is almost universal in patients who have treated their tinea cruris with topical corticosteroids (Fig. 20).
The differential diagnosis of tinea cruris includes any red, scaling infection or dermatoses that can affect this area. Candidiasis, psoriasis, lichen simplex chronicus (eczema/localized atopic dermatitis), irritant or allergic contact dermatitis, and ery-thrasma are the most likely diseases requiring differentiation.
The diagnosis is made tentatively by the location and morphology, particularly when seen in the patient with fungal infection of the feet. The diagnosis is confirmed
Figure 19 (See color insert) Classic tinea cruris shows a red plaque on the proximal, medial thighs with accentuation and scale at the periphery of the plaque.
Figure 20 Tinea cruris that is treated with a steroid as well as a topical antifungal agent is less likely to completely clear, and this patient has developed an associated fungal folliculitis manifested by red papules within the plaque.
by a microscopic examination of scrapings of the stratum corneum, culture, or response to therapy.
The treatment of tinea cruris depends upon its extent. Those patients with limited disease and no signs of fungal folliculitis usually respond to any topical azole applied once or twice a day. Miconazole, clotrimazole, econazole, and ketoconazole are those most often marketed for this problem. However, any azole used for vulvo-vaginal candidiasis is also effective and often more inexpensively available over the counter. These include tioconazole and butoconazole. Topical terbinafine used once or twice a day is also effective (53). Nystatin is useless for dermatophytosis. Extensive disease, clinical fungal folliculitis, and disease in an area of marked terminal hair are best treated with an oral medication. Griseofulvin 500 mg twice daily, terbinafine 250 mg daily, fluconazole 100/200 mg a day, and itraconazole 200 mg a day are all highly effective and safe. A trial of itraconazole given as 200 mg on two or three occasions showed cure rates of 86% to 100% (54). Patients should be reevaluated after about two weeks for clinical cure. Recurrence is common when fungal infection of the feet is present. Early treatment of recurrent disease with a topical medication is generally effective. Alternatively, onychomycosis can be more definitively treated with standard doses of itraconazole or terbinafine (Table 16).
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