TINEA (DERMATOPHYTE) INFECTIONS
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.
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.
Affects trunk and extremities: Erythematous annular scaly patches with “active border”, central clearing; #1 cause = T. rubrum.
Interdigital type: Macerated, scaly plaques in toe web spaces, can be portal of entry for cellulitis of the foot, especially in diabetics. (Tip: in recurrent leg cellulitis, look for tinea pedis!)
“Moccasin” type: Dryness, scaling and erythema of the plantar and/or lateral foot.
Vesicular type: vesicles, pustules, or bullae on the feet.
Inner thighs and inguinal folds; tinea faciei: face; tinea manuum: hands; tinea barbae: beard area.
Alopecia with scale, kerion (boggy mass), or discrete pustules; very contagious.
See onychomycosis section.
Patient education: Avoid factors which predispose to infection, absorbent powders in intertriginous areas, e.g., for tinea pedis— shower-shoes in public facilities.
Topical antifungals for tinea corporis/cruris/pedis (unless lesions are extensive): Terbinafine, ciclopirox, clotrimazole, ketoconazole applied qd or bid × 3 wk, or continue 1 wk until after resolution of lesions.
Systemic antifungals for tinea capitis.
Terbinafine (Lamisil) <20 kg = 62.5 mg po qd, 20—40 kg = 125 mg po qd, >40 mg = 250 mg po qd × 2—4 wk.