What causes a chronic fungal toenail infection lasting 30 years?

From the Guidelines

A chronic fungal toenail infection lasting 30 years is typically caused by dermatophyte fungi, most commonly Trichophyton rubrum, which have established a persistent infection in the nail bed and plate due to factors such as poor medication penetration, reduced immune response, and ideal fungal growth conditions. The infection becomes chronic due to several factors, including:

• The nail's thick structure limiting medication penetration
• Poor circulation to the toes reducing immune response
• The warm, moist environment inside shoes creating ideal conditions for fungal growth
• Age-related changes to nail thickness and reduced immune function contributing to persistence As noted in the British Association of Dermatologists' guidelines for the management of onychomycosis 1, treatment failure or relapse is a significant concern, with high recurrence rates of 40-70% reported. Treatment for such long-standing infections usually requires oral antifungal medications like terbinafine (250mg daily for 12 weeks) or itraconazole (pulse therapy of 200mg twice daily for one week per month, for three months), as topical treatments alone are rarely effective for established infections. According to the guidelines for treatment of onychomycosis 1, terbinafine is superior to itraconazole for dermatophyte onychomycosis, with cure rates of 80-90% for fingernail infection and 70-80% for toenail infection expected. Prevention of recurrence is crucial and includes:
• Keeping feet dry
• Wearing breathable footwear
• Using antifungal powders
• Disinfecting shoes regularly As highlighted in the study on systemic agents for onychomycosis 1, terbinafine has a fungicidal effect, with a low minimum inhibitory concentration (MIC) and minimal fungicidal concentration (MFC), making it an effective treatment option. Patients with diabetes or compromised immunity should seek treatment promptly, as these infections can lead to more serious complications in these populations 1.

From the FDA Drug Label

The pathogenic role of the non-dermatophytes cultured in the presence of dermatophytic onychomycosis has not been established. The clinical significance of this association is unknown The FDA drug label does not answer the question.

From the Research

Causes of Chronic Fungal Toenail Infection

• A chronic fungal toenail infection lasting 30 years can be caused by various factors, including the type of fungus, the severity of the infection, and the effectiveness of treatment 2, 3.
• Dermatophytes are the most common cause of onychomycosis, but non-dermatophyte molds (NDMs) can also be responsible, especially in warmer climates 3.
• Poor treatment outcomes and high recurrence rates can contribute to the chronic nature of the infection 2, 4.

Risk Factors for Chronic Infection

• Factors that can increase the risk of chronic fungal toenail infection include:
  • Limited treatment options and poor efficacy of available treatments 2
  • High recurrence rates after treatment 3, 4
  • Presence of comorbidities, such as diabetes or poor circulation 4
  • Failure to sanitize shoes and socks, and walking barefoot in public places 3, 4

Treatment Challenges

• Treatment of chronic fungal toenail infection can be challenging due to:
  • Limited effectiveness of topical treatments, such as ciclopirox 8% nail lacquer 2
  • High recurrence rates after oral antifungal treatment 3, 4
  • Need for long-term treatment and maintenance therapy to prevent relapse 5
  • Importance of accurate diagnosis and treatment selection based on severity and patient preference 4, 6