Onychomycosis is the most common nail disease
The prevalence increases with age
Dermatophytes are responsible for about 85% of cases, non-dermatophyte molds account for 15% of cases and onychomycosis due to yeasts are rare
Affects more frequently toenails than fingernails
Predisposing factors include age, diabetes, HIV infection, peripheral vascular impairment and peripheral neuropathies, podiatric abnormalities, sports activities, and traumatic nail disorders
Clinical diagnosis of onychomycosis always requires laboratory confirmation
Different clinical patterns of infection depend on the way by which fungi colonize the nails.
Type of nail invasion depends on responsible fungus and host susceptibility.