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The dermatophytes metabolize the keratin of the skin, hair, and nails. Hydration and occlusion of the skin facilitate infection. Although dermatophyte infections routinely affect persons who are otherwise healthy, immunocompromised patients are particularly susceptible. Bizarre presentations and failure to respond to
I. Diagnostic Evaluation of Dermatophyte Infections
A. Potassium Hydroxide Exam. Accurate diagnosis of dermatophyte infections requires a potassium hydroxide (KOH) examination. Scrapings from involved skin or nail are placed in a drop of 20% potassium hydroxide (KOH) solution on a glass slide; a coverslip is applied, and the preparation is heated gently over an alcohol lamp. Examination under a microscope reveals the septate, branching, dermatophyte infections, dermatophytes, ringworm, ring worm, tinea threadlike hyphae characteristic of dermatophytes. KOH examination of hair reveals small spores. If potassium hydroxide exam is negative, the scales may be cultured on a fungal dermatophyte infections, dermatophytes, ringworm, ring worm, tinea medium.
B. Cultures on
II. Tinea Pedis (athlete's foot)
A. The acute form of tinea pedis is characterized by Treatment of Dermatophyte Infections, ringworm ring worm, tinea sudden onset of an erythematous vesicular or bullous eruption, which is intensely pruritic and sometimes painful. It occurs interdigitally and on the soles of the feet. Acute attacks are self-limited, but recurrences are common. A sterile vesicular "id Treatment of Dermatophyte Infections, ringworm ring worm, tinea Treatment of Dermatophyte Infections, ringworm ring worm, tinea Treatment of Dermatophyte Infections, ringworm ring worm, tinea Treatment of Dermatophyte Infections, ringworm ring worm, tinea eruption" sometimes appears concomitantly on the hands.
B. The chronic form of tinea pedis is Interdigital fissures are common. Untreated, the eruption persists indefinitely. The palm on the dominant-handed side is often similarly involved ("one-hand, two-feet disease").
C. Tinea pedis is caused by Trichophyton mentagrophytes or Trichophyton rubrum. KOH examination of skin scrapings show septate hyphae. Secondary staphylococcal infections are common.
D. Management of Tinea Pedis
1. Acute disease usually can be managed with a topical antifungal. Azole creams (eg, ketoconazole [Nizoral], sulconazole [Exelderm]), allylamine creams (eg, terbinafine [Lamisil]), and ciclopirox (Loprox) are all equally effective. These agents should be applied twice daily for 2 weeks or more.
2. For refractory cases, oral griseofulvin microsize (Fulvicin U/F, Grifulvin V, Grisactin) in a single daily dose of 500 mg for 4 to 8 weeks may be prescribed. Itraconazole (Sporanox), 200 mg twice daily for 7 days, and terbinafine (Lamisil), 250 mg daily for 14 days, are effective alternatives
III. Onychomycosis (tinea unguium)
A. Onychomycosis affect the fingernails and toenails. Nail lesions of psoriasis, eczematous eruptions and ischemic arterial disease can mimic onychomycosis. The KOH test or a culture is essential to establish the proper diagnosis.
B. Onychomycosis is cause by T rubrum, and some degree of tinea pedis is usually also present. The disease usually begins at the corner of the nail as a yellowish discoloration. As it spreads, the nail begins to separate from its bed distally, resulting in irregular nail dystrophy.
C. Management of Onychomycoses
1. The presence of the fungus in the nail or its bed is confirmed by KOH examination or culture.
2. Topical treatment is ineffective. Results with griseofulvin by mouth have been disappointing, but response to newer antifungals has been excellent. Itraconazole and terbinafine are the medications of choice.
3. Itraconazole (Sporanox)
a. Toenail infection with or without fingernail involvement: 200 mg (2 capsules) by mouth daily for 90 days. Pulse therapy, 200 mg (2 capsules) bid for 1 week per month for 4 months. Itraconazole should be taken with a full meal.
b. Fingernail infections: Pulse therapy, 200 mg (2 capsules) bid for 1 week per month for 2 months.
c. Drug interactions. The medication is contraindicated in patients taking astemizole (Hismanal) and cisapride (Propulsid) because serious cardiovascular events may occur. Itraconazole also should not be used with triazolam (Halcion), midazolam (Versed), lovastatin (Mevacor), or simvastatin (Zocor).
4. Terbinafine (Lamisil) in tablet form is an effective alternative to itraconazole.
a. Fingernail infections: 250 mg (one tablet) daily by mouth for 6 weeks.
b. Toenail infections: 250 mg daily for 90 days.
5. Fluconazole (Diflucan), 150 mg PO qd, is another alternative. (One and a half of the 100 mg tablets is more economical than the 150 mg tablet.)
IV. Tinea Cruris
A. This condition is typically known as jock itch or crotch rot. It is common in men and rare in women. Tinea cruris affects the crural fold and inner aspect of one or both thighs. The source of the infection is the patient's own feet, and some degree of tinea pedis usually is also present. The condition is usually caused by T rubrum.
B. Tinea cruris usually presents as an annular lesion with central clearing and a narrow, raised, erythematous border.
C. Management of Tinea Cruris
1. Topical azoles (eg, econazole [Spectazole], sulconazole), allylamine cream (terbinafine), and ciclopirox are all equally effective. Econazole (Spectazole), apply to affected area once daily; cream: 1% [15, 30, 85 g].
2. Refractory or unusually extensive disease is best treated with 500 mg daily of oral griseofulvin microsize for 2 to 4 weeks. Itraconazole, 200 mg twice daily for 7 days, and terbinafine, 250 mg daily for
D. Allylamines (naftifine and terbinafine) are more effective against tinea, but have little activity against Candida.
1. Naftifine (Naftin), apply to affected area bid; [cream 15, 30, 60 gm]: [gel 20, 40, 60 gm]; minimal Candida coverage.
2. Terbinafine (Lamisil), apply to affected area bid; cream: 1% [15, 30 g]; minimal Candida coverage.
V. Tinea capitis
A. Tinea capitis usually is a disease of children; however, tinea corporis may develop in adults in the same household. The disease appears as patchy scalp hair loss in one or more slightly erythematous, scaly, maculopapular lesions, reaching sizes of 4 to 6 cm or larger. Hairs within the patches fracture, leaving frosted stumps that are 1 to 2 mm in length. Lesions may become tender, inflammatory nodules (kerion). Lesions are often secondarily infected by
B. KOH examination of infected hair shows many small spores.
C. Management of Tinea Capitis
1. Griseofulvin microsize by mouth is the medication of choice. Itraconazole and terbinafine are effective alternative treatments.
2. Recommended griseofulvin dosage: Adults: 250 mg twice daily for 6 to 12 weeks. Children: 11 mg/kg for the same length of time. When griseofulvin ultramicrosize is used, doses can be reduced 30%. Both medications should be taken with a glass of milk or a meal to enhance gastrointestinal absorption.