Fungal Infections
A. Candidiasis. Caused by Candida albicans. Seen as thrush diaper dermatitis, perineal infections, and intertriginous dermatitis. Diagnosis is by clinical exam, and microscopic examination of skin scraping in 10% KOH reveals yeast forms and budding hyphae. Treatment of choice miconazole 2% cream BID to affected areas for superficial fungal infections. Chronic mucocutaneous involvement can be treated with ketoconazole 200 to 600 mg PO daily (alternatives itraconazole or fluconazole). Multifocal invasive disease requires intravenous amphotericin B. Persons who present with recurrent infections should have an investigation of other causes such as diabetes mellitus, hypoparathyroidism,Addison’s disease, malignancies, HIV. Use of steroids and antibiotics is also a predisposing factor.
B. Dermatophytoses (tinea). The fungi belonging to the genera Trichophyton, Microsporum, and Epidermophyton infect the stratum corneum of epidermis, hair. and nails. Commonly referred to by the locus of infection, that is, tinea unguis (nails), tinea pedis (foot, athlete’s foot), tinea cruris (perineum, jock itch), tinea corporis (body, ringworm), and tinea capitis (scalp and hair). Lesions can appear as grayish, scaling patches that can be quite pruritic and may lead to autoinoculation or scalp alopecia. Skin scraping in 10% KOH will demonstrate fungal hyphae. Infected hairs when examined under Wood’s light will fluoresce a green-yellow color. Treatment is as follows:
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Tinea corporis (body, ringworm), tinea cruris (perineum, jock itch), tinea pedis (foot, athlete’s foot). Topical tolnaftate or clotrimazole TID until clear and then 1 to 2 weeks longer.
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Tinea capitis (scalp and hair). Micronizedgriseofulvin is usually used for up to 4 to 8 weeks. Adjunctive therapy includes selenium sulfide shampoo q2-3 days.
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Tinea unguis, or onychomycosis (nails). Griseofulvin 500 mg BID for a period of 4 to 6 months or itraconazole 200 mg BID for 4 months (1 week on; 3 weeks off); latter regimen is very expensive. An alternative is terbinafine 250 mg PO QD for 12 weeks or BID for 1 week of the month for 3 or 4 months.
C. Pityriasis (tinea) versicolor. Appears as slightly pigmented superficial tan scaling plaques of various sizes, primarily on the neck, trunk, and proximal area of the arms. With sun exposure, the infected regions do not tan and appear hypopigmented. Usually caused by Malassezia furfur (Pityrosporum orbiculare). Diagnosis is by clinical exam and KOH preparations of skin scraping. Treatment can be with topical miconazole 2% cream twice daily or washing with zinc or selenium shampoos daily for 2 to 3 weeks. Although not FDA approved, ketoconazole 400 mg in a single dose orally is 97% effective in adults. Have patients exercise to a sweat and not shower for 2 to 4 hours.
Comments
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