Brief Overview About Onychomycosis

Abstract

Background: Onychomycosis is derived from the Greek words’ “onyx” meaning nail and “mykes” meaning fungus. It has been known that onychomycosis in children is less common than in adults, but its frequency has been rising. Very well-established predisposing factors for onychomycosis are trauma, old age, and previous infections with tinea pedis, poor nail trimming, sports and fitness activities, smoking, occlusive shoes, asymmetric gait nail unit syndrome and hallux valgus, comorbidities, such as diabetes, obesity, immunosuppression and malignancies are also associated with increased risk, also it is more common in psoriatic patients than healthy individuals and it is estimated that psoriatic patients have a 50% chance of developing onychomycosis compared with non-psoriatic patients. Biofilms have recently been acknowledged to play an important role in the pathophysiology of onychomycosis. Although fungi were previously thought to be planktonic (defined as in suspension, free floating, and acting independently), recent evidence supports the formation of biofilms. Suggested mechanism of biofilms is that they are stationary and not moving microbial communities that are fixed to biological surfaces (such as the nail plate) via an extracellular matrix that enclose the biofilms, so they contribute to resistance to antifungal agents, increased virulence and invasion of immune systems. Dermatophytes, NDM and yeast all form biofilms in vitro especially T. rubrum and T. mentagrophytes begin forming biofilms after 3 hours and are fully formed by 72 hours. Dermatophytes cause about 90% of toenail and 75% of fingernail onychomycosis mainly anthropophilic dermatophytes particularly by T. rubrum and T. mentagrophytes. Non-dermatophyte molds (NDM) that can cause onychomycosis account for 20% of cases worldwide and include Aspergillus species, Scopulariopsis species, Fusarium species and Acremonium species; Yeast onychomycosis is caused mainly by Candida Albicans as about 70% of all yeast infection, the rest is caused by Candida tropicalis and Candida parapsilosis, patients with chronic mucocutaneous candidiasis and immunodeficiency are more likely infected with the yeast organisms, especially in the fingernails