dermatophytosis

Dermatophytosis, or tinea, refers to fungal infections of keratinized tissues caused by dermatophyte fungi of the genera Trichophyton, Microsporum, and Epidermophyton. The fungi feed on keratin and invade the stratum corneum, hair, and nails. Transmission occurs via direct contact with an infected person, animal, or contaminated object, and some species are more commonly associated with particular body sites.

Clinical presentations vary by site and include tinea corporis (ring-shaped lesions on the body), tinea cruris (groin), tinea pedis (foot), tinea manuum (hand), tinea capitis (scalp), tinea barbae (beard), and tinea unguium (nails). Lesions are typically pruritic with scaling; nail infections may cause thickened, discolored nails. In children, tinea capitis is especially common.

Diagnosis is supported by microscopy of skin scrapings in potassium hydroxide showing hyaline, septate hyphae and by fungal culture. Wood’s lamp examination can aid in selecting species for some dermatophytes; polymerase chain reaction assays are available in specialized laboratories but are not universally required.

Treatment: Most localized skin infections respond to topical antifungals such as terbinafine, itraconazole, or azoles applied daily for 1–4 weeks. Extensive disease, tinea corporis with widespread involvement, tinea capitis, or tinea unguium often requires systemic therapy for 4–12 weeks (or longer for nails). Griseofulvin is used less commonly in developed countries. Monitor for hepatic adverse effects with oral antifungals as indicated.

Prevention includes keeping skin dry, avoiding shared personal items, laundering contaminated items, and treating infected pets. With appropriate treatment, most cases resolve, though recurrences are common.