• 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



  • Occurs in 2–10% of general population
  • Predominant age: 20% in adults >60 years of age, 50% in adults >70 years of age (1)
  • Rare before puberty
  • Prevalence 15–40% in persons with human immunodeficiency infection
  • Estimated 50% of all nail disorders in the outpatient setting (1)

Etiology and Pathophysiology

  • 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 cause 90% of toenail and most of fingernail onychomycoses.
  • Yeasts, especially Candida, may involve fingernails (not uncommonly) or toenails.
  • Dermatophytes can invade normal keratin, whereas nondermatophyte molds invade altered keratin (dystrophic/injured nails).

Risk Factors

  • Older age
  • Tinea pedis
  • Occlusive footwear
  • Cancer/diabetes/psoriasis
  • Peripheral vascular disease
  • Cohabitation with others with onychomycosis
  • Immunodeficiency
  • Communal swimming pools
  • Smoking
  • Peripheral vascular disease
  • History of nail trauma
  • 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 (2)

Commonly Associated Conditions

  • Immunodeficiency/chronic metabolic disease (e.g., diabetes)
  • Tinea pedis/manuum

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