Dermatophytoses are fungal infections of keratin in the skin and nails (nail infection is called tinea unguium—see Nail Disorders: Onychomycosis). Symptoms and signs vary by site of infection. Diagnosis is by clinical appearance and by examination of skin scraping on potassium hydroxide wet mount. Treatment varies by site but always involves topical or oral antifungal drugs.
Dermatophytes are molds that require keratin for nutrition and must live on stratum corneum, hair, or nails to survive. All human infections are caused by Epidermophyton , Microsporum , and Trichophyton spp. These differ from candidiasis in that they are rarely if ever invasive. Transmission is person-to-person, animal-to-person, and rarely, soil-to-person. The organism may persist indefinitely. Most people do not develop clinical infection; those who do may have impaired T-cell responses from an alteration in local defenses (eg from trauma with vascular compromise) or from primary (hereditary) or secondary (eg, diabetes, HIV) immunosuppression.