Fungal Nail Infections (Onychomycosis): A Never-Ending Story?

The great majority of superficial fungal infections are caused by dermatophytes, which belong to one of three genera (Trichophyton, Epidermophyton, and Microsporum), with T. rubrum being the most prominent cause of nail infection (Figure 1). Table 1 summarizes the prevalence of various superficial fungal infections in different geographic areas [1]. Among superficial fungal infections, by far the most difficult to cure is toenail onychomycosis (Figure 2). The prevalence of onychomycosis has been reported to be as high as 23% across Europe [2] and 20% in East Asia [3]. In North America, the incidence of onychomycosis is up to 14% [4], with fungal infection responsible for 50% of all nail disease [5]. With millions of dollars being spent annually on oral and topical prescriptions, laser treatments, over-the-counter products, and home remedies, it is obvious that people are still bothered by their fungal toenail infections and are determined to get rid of them. Unfortunately, this is easier said than done. To successfully cure toenail onychomycosis requires long treatment duration that may extend to a full year. Even then, complete cure, defined as clinical cure (implying nail clearing) plus mycological cure (both negative microscopy and dermatophyte culture), is often unattainable.