What are the diagnosis and management options for onychomycosis (toenail fungus)?

Diagnosis and Management of Toenail Fungus (Onychomycosis)

Laboratory confirmation of fungal infection is essential before initiating treatment for onychomycosis, with oral terbinafine being the first-line treatment for most cases due to its superior efficacy and lower relapse rates. 1, 2

Diagnosis

Clinical Presentation

• Distal lateral subungual onychomycosis (DLSO): Most common form, begins at distal/lateral edge of nail
• Superficial white onychomycosis (SWO): White patches on nail surface
• Proximal subungual onychomycosis (PSO): Begins at proximal nail fold, often seen in immunocompromised patients
• Total dystrophic onychomycosis: Complete nail destruction

Diagnostic Testing

1. Sample Collection:

   • Subungual debris from most proximal part of infection (using dental scraper)
   • For onycholytic nails: Cut back nail and scrape underside plus nail bed
   • Collect as much material as possible due to paucity of fungal elements 1

2. Laboratory Confirmation (mandatory before treatment):

   • Direct microscopy with 20% potassium hydroxide (KOH)
   • Fungal culture on Sabouraud's glucose agar (incubate 3+ weeks)
   • Consider histopathology with periodic acid–Schiff staining in difficult cases 1

3. Advanced Diagnostic Methods:

   • Molecular techniques (PCR) for faster results (<2 days)
   • Calcofluor white staining to enhance visualization 1

Caution: Clinical diagnosis alone is inadequate - 50% of nail dystrophies are non-fungal in origin. Most common cause of treatment failure is incorrect diagnosis 1

Treatment

Oral Antifungal Therapy (First-line for moderate-severe cases)

1. Terbinafine (First choice):

   • Dosage: 250 mg daily for 6 weeks (fingernails) or 12-16 weeks (toenails)
   • Advantages: Highest cure rates, fungicidal, fewer drug interactions
   • Monitoring: Baseline liver function tests and complete blood count
   • Contraindications: Hepatic impairment 1, 2

2. Itraconazole (Alternative):

   • Dosage: 200 mg twice daily for 1 week per month (pulse therapy)
   • Fingernails: 2 pulses; Toenails: 3 pulses
   • Advantages: Effective against both dermatophytes and Candida
   • Contraindications: Heart failure, hepatotoxicity 1

3. Fluconazole (Second-line):

   • Dosage: 150-450 mg weekly for 3 months (fingernails) or 6+ months (toenails)
   • Consider when terbinafine or itraconazole cannot be used
   • Monitoring: Baseline and periodic liver function tests 1

4. Griseofulvin (Third-line):

   • Dosage: 500-1000 mg daily for 6-9 months (fingernails) or 12-18 months (toenails)
   • Take with fatty food to increase absorption
   • Lower efficacy, higher relapse rates, longer treatment duration 1

Topical Antifungal Therapy (For mild cases or when oral therapy contraindicated)

1. Amorolfine 5% nail lacquer:

   • Application: Once or twice weekly for 6-12 months
   • Efficacy: ~50% cure rate 3

2. Ciclopirox 8% nail lacquer:

   • Application: Once daily for up to 48 weeks
   • Requires monthly removal of unattached infected nail 4

3. Tioconazole 28% solution:

   • Application: Twice daily for 6-12 months 1

Combination Approaches

• Mechanical nail debridement plus topical agent for thick nails or dermatophytoma
• Chemical avulsion with 40% urea for very thick nails
• Surgical removal may be necessary for dermatophytoma 3

Special Populations

Children

• Griseofulvin is the only licensed oral antifungal for children
• Terbinafine dosing by weight: <20kg: 62.5mg/day; 20-40kg: 125mg/day; >40kg: 250mg/day 1

Immunocompromised Patients

• More aggressive treatment often required
• Higher recurrence rates
• Consider longer treatment courses 1

Candida Nail Infections

• More common in fingernails and women
• Itraconazole more effective than terbinafine 1

Prevention of Recurrence

• Keep nails short and clean
• Wear protective footwear in public areas
• Apply antifungal powders to shoes and feet
• Change socks daily
• Clean athletic footwear periodically
• Treat all infected family members simultaneously 3

Important: Recurrence rates for onychomycosis are high (40-70%), making prevention crucial 3

Treatment Monitoring

• Review after 3 months to assess response
• Continue treatment until clinical and mycological cure
• Consider culture at end of treatment to confirm mycological clearance in high-risk groups 1

Onychomycosis should not be considered a trivial disease, as it can lead to complications such as cellulitis in elderly or diabetic patients, affecting quality of life and potentially causing serious morbidity 1.