Posted on December 31, 2010, under Anti-Infectives.
SUPERFICIAL FUNGAL INFECTIONS: TINEA, TINEA PEDIS, ETCTineaTinea infections are caused by dermatophytes from three genera, Trichophyton, Microsporum, and Epidermophyton. The lifetime risk of dermatophyte infection is between 10% and 20%. These infections are typically named for the site that is infected.Because other skin diseases mimic fungal infections, it is best to confirm the presence of fungus. Culture can be reserved for complicated cases, but it is very simple to perform a potassium hydroxide (KOH) preparation for microscopy. Scales should be scraped from the leading edge of lesions and placed on a microscope slide. One or two drops of KOH (10-20%) are added and a cover slip placed on top. The slide is then either heated or allowed to sit at room temperature for 10 to 15 minutes. A microscope is then used to search for the branching hyphae characteristic of dermatophyte infections. A drop of ink or fungal stain can make the hyphae easier to find.
Tinea PedisTinea pedis, or athlete’s foot, is the most common dermatophytic infection. Tinea pedis typically occurs in hot and humid weather when the patient is wearing occlusive footwear. It can present in three patterns (sometimes all in the same patient):- Interdigital (especially third and fourth spaces) maceration and cracking- Scaling, hyperkeratotic lesions in a ballet shoe or moccasin distribution- Scattered, very pruritic, vesiculobullous lesions
Tinea cruris Tinea cruris, or jock itch, is a caused by Epidermophyton floccosum or Trichophyton rubrum infection of the intertriginous areas in male patients.
Tinea CorporisTinea corporis, or ringworm, is caused by T. rubrum or by Trichophyton verrucosum or Microsporum canis (from animal contact). Tinea corporis can refer to tinea anywhere except the scalp, beard, hands, or groin. The classic ringworm appearance demonstrates annular plaques with erythema and scaling. The center clears to a dusky or brown color as the lesion extends radially. Unlike other tinea infections, tinea corporis occurs in exposed areas.
TreatmentFirst-line treatment for tinea is topical, with allylamines (naftifine, butenafine, terbinafine) being slightly more effective. Treatment should be continued for 1 week after cure. This will typically take 2 weeks for tinea corporis and tinea cruris. Tinea pedis may require 4 weeks of treatment. Chronic or resistant cases may require the use of oral agents such as itraconazole, terbinafine, griseofulvin, or once-weekly fluconazole. Environmental factors are also important in treatment and prevention. Keeping clothing, shoes, and skin dry can be very helpful. Treating shoes with antifungal powder may also be helpful. When tinea is especially inflamed and pruritic, some clinicians will use a topical steroid in conjunction with antifungal therapy, at least early in therapy. This approach helps to alleviate symptoms quickly and may even hasten resolution of the infection.*114/348/5*