The epidemiological profile of onychomycosis: cross-sectional study and systematic review

• Grant number: 23/07363-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2024
• End date: October 31, 2025
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Gil Benard
• Grantee: Sharon Hameiry
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Onychomycosis is the most common nail condition in adults, corresponding to about 50% of all nail diseases. Its prevalence is estimated at 5.5% of the world population and 90% are caused by dermatophyte fungal species, especially Trichophyton rubrum and Trichophyton interdigitale. Despite this, onychomycosis caused by non-dermatophyte molds and mixed infections has been reported more recently, reinforcing the importance of etiological identification, since the effectiveness of available treatments may be species dependent. The combination of direct mycological examination with potassium hydroxide and fungal culture is considered the gold standard for the diagnosis of onychomycosis, but other techniques such as PCR and staining used in histopathology have shown promise for this purpose, minimizing false negatives. Among the drugs available, terbinafine has been used as the first line for treating dermatophytosis since 1996, because by inhibiting the enzyme squalene epoxidase, it interferes with the ergosterol synthesis - an essential component of the cell membrane - which gives it the characteristic fungicidal activity. However, in recent years we have seen the emergence of terbinafine resistance among Trichophyton species. The reports, initiallydocumented in India, progressively became a reality in several other countries. Given thisscenario and possible cases of resistance not yet detected in our country, this study aims toinvestigate the epidemiological profile of onychomycosis in the selected sample, identifypossible resistant species, and report these findings, which have a relevant impact on publichealth. Because it is a highly prevalent disease in all social classes, has a high individualsocial impact, high transmissibility, and potential deleterious factors when left untreated,better knowledge of onychomycosis, its causative agents, and the profile of resistance to antifungals contributes to the appropriate management of this mycosis.