What is the best treatment for onychomycosis caused by Cladosporium and Pithomyces?

Treatment of Onychomycosis Caused by Cladosporium and Pithomyces

Itraconazole is the preferred treatment for onychomycosis caused by Cladosporium and Pithomyces due to its broader antimicrobial coverage for nondermatophyte moulds compared to terbinafine. 1

Diagnostic Confirmation

Before initiating treatment, proper diagnosis is essential:

• Confirm the diagnosis through microscopic examination with potassium hydroxide (KOH), mycological culture, or nail biopsy 2
• Multiple samples may be required to confirm nondermatophyte moulds as causative agents, as they can be contaminants 1

Treatment Algorithm for Cladosporium and Pithomyces Onychomycosis

First-line Treatment:

• Itraconazole 200mg daily for 12 weeks continuously OR
• Itraconazole pulse therapy: 200-400mg daily for 1 week per month, for 3-4 months 1

Second-line Options:

• Topical therapy for mild cases or when systemic therapy is contraindicated:
  • Ciclopirox 8% nail lacquer (mycological cure rates of 34%) 2
  • Amorolfine 5% nail lacquer (approximately 50% efficacy in distal nail infections) 2

Treatment Considerations:

• In vitro studies show Aspergillus has excellent susceptibility to itraconazole, followed by miconazole, ketoconazole, and terbinafine 1
• Terbinafine demonstrated the lowest activity against the majority of nondermatophyte moulds in vitro 1
• Clinical efficacy does not always correlate with in vitro activity for nondermatophyte moulds 1

Monitoring and Follow-up

• Monitor liver function for itraconazole treatment durations longer than 1 month 1
• Be aware of drug interactions with itraconazole, particularly with anticoagulants, antihistamines, antipsychotics, anxiolytics, digoxin, cisapride, ciclosporin, and simvastatin 1
• Complete clinical and mycological cure may take 6-12 months due to the slow growth rate of nails

Prevention of Recurrence

To prevent recurrences (which occur in 40-70% of cases):

• Maintain short and clean nails
• Dry feet thoroughly after bathing
• Wear cotton socks and change them daily
• Apply antifungal powders to shoes and feet
• Avoid sharing nail clippers
• Wear protective footwear in public areas
• Treat concomitant fungal infections promptly 2

Common Pitfalls and Treatment Failure

• Not confirming diagnosis before treatment: Always verify the causative organism
• Inadequate treatment duration: Nondermatophyte mould infections often require longer treatment courses
• Not addressing predisposing factors: Treat concomitant fungal infections
• Unrealistic expectations: Inform patients that visible improvement takes months
• Management of treatment failure may include:
  • Alternative antifungal drug
  • Partial nail removal plus antifungal therapy
  • Complete nail avulsion combined with antifungal therapy 2

While terbinafine is typically the first-line treatment for dermatophyte onychomycosis with efficacy of 70-80% for toenail infections 2, it has limited activity against nondermatophyte moulds like Cladosporium and Pithomyces, making itraconazole the preferred option for these specific pathogens.