Onychomycosis (Nail Fungus)

Onychomycosis refers to any fungal infection of the toenails or fingernails. More than 90% of cases are caused by the dermatophyte Trichophyton rubrum, while yeasts and nondermatophytes are responsible for only a small percentage of cases. Typically, the toenails are affected more frequently than fingernails. Infections of the toenails are also generally more difficult to treat, requiring a longer duration of therapy compared with fingernail infections. Onychomycosis causes nails to thicken, discolor, disfigure, and split. This entry reviews the risk factors associated with onychomycosis as well as its clinical impact, classification, diagnosis, and treatment.