Onychomycosis is a fungal infection of the nail unit caused by dermatophytes (most commonly Trichophyton rubrum), yeasts, or non-dermatophyte molds, leading to onycholysis, subungual hyperkeratosis, discoloration, and nail dystrophy. It is a chronic condition with cosmetic and functional impact, and a reservoir for tinea pedis recurrences. Accurate mycologic confirmation guides therapy. Oral terbinafine is first-line for dermatophyte infections; itraconazole is an alternative. Topical agents (efinaconazole, tavaborole, ciclopirox) are options for mild disease or when systemic therapy is contraindicated. Adjunctive debridement improves outcomes. Recurrence is common; preventive foot care is essential.
Epidemiology and Risk Factors
- Prevalence increases with age; higher in diabetics, immunosuppressed, peripheral vascular disease, tinea pedis, occlusive footwear, nail trauma.
- Toenails affected far more than fingernails.
Classification
- Distal lateral subungual onychomycosis (DLSO) – most common.
- Proximal subungual onychomycosis (PSO) – consider immunosuppression.
- White superficial onychomycosis (WSO).
- Endonyx onychomycosis.
- Total dystrophic onychomycosis (TDO).
- Candida onychomycosis (paronychia, fingernails in wet-work).
Diagnosis
- Confirm before systemic therapy.
- KOH prep of nail scrapings, fungal culture, and/or PAS stain of nail clippings (highest sensitivity).
- PCR where available for rapid species ID.
- Assess for coexistent tinea pedis and treat concurrently.
Management
- General and adjunctive measures
- Routine debridement/thinning of thickened nails to enhance penetration.
- Treat tinea pedis (topical allylamines/azoles) and disinfect footwear, socks; keep feet dry; avoid occlusive shoes.
- Patient counseling on long durations to see results (toenail outgrowth ~12–18 months).
- Systemic therapy (dermatophyte-predominant)
- Terbinafine
- Dosing: 250 mg daily for 12 weeks (toenails) or 6 weeks (fingernails).
- Efficacy: highest mycologic and clinical cure rates for dermatophytes.
- Monitoring: baseline LFTs; subsequent monitoring individualized; caution with liver disease; drug interactions via CYP2D6.
- Itraconazole
- Continuous: 200 mg daily for 12 weeks (toenails).
- Pulse: 200 mg bid for 1 week per month ×2 (fingers) or ×3–4 (toes).
- Broader spectrum (Candida, some molds); interactions via CYP3A4; avoid in heart failure.
- Fluconazole (off-label)
- 150–300 mg weekly for 6–12 months; useful for Candida or when others not tolerated.
- Topical therapy (mild disease, ≤50% nail plate involvement without matrix disease; or systemic contraindications)
- Efinaconazole 10% solution qd × 48 weeks.
- Tavaborole 5% solution qd × 48 weeks.
- Ciclopirox 8% lacquer qd with weekly removal and debridement.
- Topicals have lower cure rates; adherence and debridement critical.
- Non-dermatophyte molds and Candida
- Confirm with repeated cultures/PCR; often require itraconazole or fluconazole; consider combination topical + oral; address paronychia in Candida (reduce wet work, topical azoles).
- Combination and procedural approaches
- Oral + topical combinations may reduce relapse.
- Laser and device therapies: mixed evidence; consider adjunctively, not as monotherapy.
- Surgical/chemical nail avulsion for severe isolated dystrophic nails, followed by antifungals.
- Prevention of relapse
- Treat household/communal sources; antifungal powders/sprays; avoid barefoot in communal areas.
- Maintenance topical antifungal 1–2 times weekly after cure can reduce recurrence.
Prognosis
- Cure rates vary by agent and adherence; relapse/reinfection common within 2–3 years without prevention.
- Diabetics benefit from treatment (reduced ulcer/infection risk).
References (recent guidelines and key reviews)
- Dermatophyte onychomycosis management guidelines, 2022–2024.
- Comparative efficacy/meta-analyses of terbinafine vs itraconazole and topicals, 2021–2024.
- PAS/PCR diagnostic accuracy studies, 2021–2024.