Epidemiology of onychomycosis in special-risk populations.

A person's susceptibility to onychomycosis and the course of the disease once the nails are infected are functions of the interaction of the fungal agent, the host, and environmental factors. The disease is reported to have an overall prevalence of 2% to 13%, but the prevalence is much higher in certain populations, such as older people and those with immunosuppressive conditions. Although onychomycosis may be merely a nuisance and an embarrassment for healthy individuals, some morbidity is seen with all population groups, but especially high-risk patients: diabetics, patients infected with human immunodeficiency virus (HIV), patients with acquired immunodeficiency syndrome (AIDS), and patients with other types of immunosuppression (eg, transplant recipients and patients on long-term corticosteroid therapy). Whether the increased prevalence of onychomycosis in the elderly (up to 30% by age 60) is related to changes in immune function is not known.