• 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



  • 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

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