What is the best initial approach for a young, asymptomatic patient with a history of fungal infection, previously confirmed by nail clipping for fungal culture and sensitivity testing, who presents with deformed fingers and has had liver function tests (LFTs) in the past, now seeking further treatment?

Initial Management of Suspected Recurrent Onychomycosis

Before initiating systemic antifungal therapy, you must obtain fresh nail clippings for mycological confirmation with both microscopy and culture, and check baseline liver function tests. 1

Step 1: Confirm Active Fungal Infection

• Do not commence treatment before mycological confirmation of infection 1
• Obtain new nail clippings for both microscopy (KOH preparation) and fungal culture with sensitivity testing 1
• A positive culture from one year ago is insufficient to guide current treatment, as clinical cure criteria require knowing the current infection status 1
• The deformed appearance alone cannot distinguish between active infection, post-infectious nail dystrophy, or traumatic changes 1

Step 2: Obtain Baseline Liver Function Tests

• Measurement of serum transaminases (ALT and AST) is advised for all patients before taking terbinafine 2
• This is mandatory even though the patient is young, asymptomatic, and has no known liver disease 2
• Patients with pre-existing liver enzyme abnormalities are at higher risk for hepatic adverse reactions during antifungal treatment 3
• Liver problems can lead to the need for liver transplant or death with oral antifungals 2

Step 3: Wait for Results Before Treatment

Do not offer treatment immediately - wait for:

• Mycological confirmation (microscopy AND culture positive) 1
• Baseline liver function test results 2
• Culture and sensitivity results to guide appropriate antifungal selection 1

Rationale for Waiting

• Treatment failure rates of 20-30% occur even with optimal therapy, often due to inappropriate drug selection or resistant organisms 1
• Dermatophytes are the most common cause, but yeasts and non-dermatophyte moulds require different interpretation and treatment approaches 1
• Terbinafine is superior to itraconazole for dermatophyte onychomycosis, but itraconazole is preferred for candidal nail infections 1
• Starting empiric therapy without confirmation risks unnecessary hepatotoxicity, drug interactions, and treatment failure 2

Step 4: Once Results Return

If Dermatophyte Confirmed:

• Terbinafine 250 mg daily is first-line treatment 1
• Duration: 6 weeks for fingernails, 12 weeks for toenails 1, 2
• Expected cure rates: 80-90% for fingernails, 70-80% for toenails 1

If Candida Confirmed:

• Itraconazole 400 mg daily for 1 week per month (pulse therapy) is most effective 1
• 2 pulses for fingernails, 3-4 pulses for toenails 1

Critical Safety Monitoring

• Advise the patient to immediately report persistent nausea, anorexia, fatigue, vomiting, right upper abdominal pain, jaundice, dark urine, or pale stools 2
• Discontinue treatment immediately if these symptoms develop 2
• Taste disturbance occurs commonly and may become permanent; patients should report this promptly 2
• The optimal clinical effect appears months after treatment completion due to time required for healthy nail outgrowth 2

Common Pitfall to Avoid

The most critical error would be starting systemic antifungal therapy without current mycological confirmation and baseline liver tests - this violates fundamental treatment guidelines, exposes the patient to unnecessary hepatotoxic risk, and may result in treatment failure if the wrong organism or no active infection is present 1, 2.