Onychomycosis

Description

• Fungal infection of fingernails/toenails
• Caused mostly by dermatophytes but also yeasts and nondermatophyte molds
• Toenails are more commonly affected than fingernails.
• Synonym: tinea unguium

Epidemiology

Prevalence

• Worldwide prevalence is approximately 5.5%.
• More common in adults than children; prevalence increases with age; 35% of adults aged >65
• Rare before puberty
• Prevalence 15–40% in persons with human immunodeficiency virus (HIV)
• Estimated 50% of all nail disorders in the outpatient setting

Etiology and Pathophysiology

• Inoculation of nail with dermatophytes, nondermatophyte molds, or yeasts
• Dermatophytes: Trichophyton (Trichophyton rubrum most common), Epidermophyton, Microsporum
• Yeasts: Candida albicans (most common), Candida parapsilosis, Candida tropicalis, Candida krusei
• Molds: Scopulariopsis brevicaulis, Hendersonula toruloidea, Aspergillus sp., Alternaria tenuis, Cephalosporium, Scytalidium hyalinum
• Dermatophytes, notably Trichophyton, cause 90% of toenail and 75% of fingernail onychomycoses.
• Yeasts, especially Candida, may involve fingernails (not uncommonly) or toenails.

Risk Factors

• Older age, occlusive footwear, tinea pedis
• Cancer/diabetes/psoriasis
• Peripheral vascular disease
• Living with others with onychomycosis, communal swimming pools
• Peripheral vascular disease
• Smoking
• Immunodeficiency
• Autosomal dominant genetic predisposition

General Prevention

• Keeping feet cool and dry
• Avoiding occlusive footwear
• Using sandals in public locker rooms and swimming pools
• Discarding or treating of infected footwear and socks (1)

Commonly Associated Conditions

• Immunodeficiency (acquired immune deficiency syndrome and transplant patients) and chronic metabolic disease (e.g., diabetes)
• Tinea pedis/manuum