Fungal Skin Infection

Infections by dermatophytes ("tinea": Trichophyton, Microsporum, Epidermophyton) or yeasts (Candida:l intertriginous/mucocutaneous; Malassezia:tinea versicolor, seborrheic dermatitis).

This entry covers general principles; see Tinea Corporis for detailed body ringworm.

Classified by site: tinea capitis (scalp), tinea corporis (body), tinea cruris (groin), tinea pedis (feet), tinea unguium/onychomycosis (nails), tinea versicolor (Malassezia, trunk), candidal intertrigo (skin folds).

• Tinea pedis: interdigital maceration or moccasin-distribution scaling, itching

• Tinea cruris: erythematous scaly plaques, central clearing, spares scrotum (distinguishes from candida)

• Tinea unguium: thickened, discolored, brittle nail with subungual debris

• Tinea versicolor: hypo/hyperpigmented macules with fine scale, trunk/upper arms, more visible with tanning

• Candidal intertrigo: beefy red macerated skin folds with satellite pustules : associated diabetes/obesity/immunosuppression/antibiotics

Often clinical.

KOH microscopy of scrapings confirms hyphae (dermatophyte) or "spaghetti and meatballs" (Malassezia).

Fungal culture if treatment failure/atypical. Nail clippings for onychomycosis before prolonged oral treatment.

Differentials: psoriasis, eczema, contact dermatitis, erythrasma (coral-red Wood's lamp fluorescence).

• Localized (tinea pedis/cruris/corporis): topical terbinafine cream od-bd × 1-2 weeks, or clotrimazole/miconazole bd × 2-4 weeks

• Extensive/recalcitrant/tinea capitis/onychomycosis: oral terbinafine 250mg od (6 weeks fingernails, 12 weeks toenails; 2-6 weeks tinea capitis/extensive corporis) : check LFTs baseline and during treatment

• Tinea capitis always requires oral therapy (topical insufficient) ; griseofulvin or terbinafine, weight-based; adjunct antifungal shampoo reduces transmission

• Tinea versicolor: topical selenium sulfide/ketoconazole shampoo daily × 1-2 weeks; oral itraconazole/fluconazole for extensive/recurrent disease; pigment changes resolve slowly

• Candidal intertrigo: topical clotrimazole/miconazole bd, keep dry, address risk factors

Referral: dermatology for recalcitrant/atypical infection, extensive onychomycosis with comorbidity concerns.