Tinea (Dermatophyte) Infections
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Etiology: Dermatophytes digest and invade keratin and may infect skin, nails, and hair; incubation = 1—3 wk. Trichophyton, Microsporum, Epidermophyton species commonly involved. Human-to-human (anthropophilic), animal-to-human (zoophilic; intense inflammation), or soil-to-human (geophilic; moderate inflammation) spread.
Risk Factors: Hot, humid environments, sweating or maceration of the skin, occlusive footwear, diabetes mellitus, immunosuppression (e.g., AIDS).
History: Asymptomatic; occasionally mild pruritus.
Physical: Scalp hair and general body surfaces mostly affected during childhood; hand, foot, or nail infections are more common after puberty.
- Immunologic response to a dermatophyte infection may result in a dermatophytid or "id" reaction: Vesicular eruption on acral surfaces, especially the palms.
Investigations: Skin scraping analysis with KOH prep—Septate hyphae branching at various angles are seen; fungal culture (~4 wk to ID dermatophyte species); biopsy—PAS or GMS stain can reveal presence of fungal elements.
DDx: Eczema, granuloma annulare, psoriasis.
See Topic(s):