Updated: 12/16/2021

Onychomycosis

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  • Snapshot
    • A 7-year-old boy presents to his pediatrician’s office for a white rash on his nails. His mom reports that he has a history of tinea pedis and tinea manuum and thought that this might be related. On physical exam, his left fourth and fifth finger have a thin, white, and powder-like discoloration of the nail plate. He is given topical therapy for this rash.
  • Introduction
    • Clinical definition
      • a dermatophytosis
        • superficial fungal infection of the nail
          • involving nail bed and underside of nail plate
          • also called tinea unguium
        • types of onychomycosis
          • distal and lateral subungual onychomycosis
            • most common
            • affects nail bed and underside of nail plate
            • due to Trichophyton rubrum
          • superficial white onychomycosis
            • common in children
            • affects surface of nail plate
            • due to Trichophyton mentagrophytes
          • proximal subungual onychomycosis
            • uncommon
            • usually in immunocompromised patients
            • affects proximal nail plate
            • due to Trichophyton rubrum
    • Associated conditions
      • tinea pedis
      • tinea cruris
  • Epidemiology
    • Prevalence
      • 3% prevalence in adults
      • 20% prevalence in adults > 60 years old
    • Demographics
      • male > female
      • adults > 60 years old
    • Location
      • toenails > fingernails
    • Risk factors
      • moist and warm environment
      • increasing age
      • immunosuppression
      • occlusive shoes
      • communal baths
  • Etiology
    • Pathogenesis
      • fungal infection of keratinized tissue of nail plate
    • Dermatophytes
      • Trichophyton
        • most commonly Trichophyton rubrum
      • Microsporum
      • Epidermophyton
    • Candida spp.
      • less common cause of onychomycosis
  • Presentation
    • Symptoms
      • asymptomatic
    • Physical exam
      • distal and lateral or proximal subungual onychomycosis
        • thickened with white, yellow, or brown discoloration
        • thickened nail may separate from nail bed (onycholysis)
        • most commonly affects first or fifth nail
      • superficial white onychomycosis
        • white discoloration of nail plate
        • powder-like
  • Studies
    • KOH preparation
      • skin scrapings at active edge of lesion mixed with KOH
      • presence of septated hyphae and spores indicates fungal infection
    • Calcofluor white staining
      • presence of branching hyphae
    • Fungal culture
      • performed if confirmation is needed or if KOH or calcofluor testing is negative
    • Making the diagnosis
      • usually based on clinical history and physical exam but confirmation with the aforementioned tests are recommended
  • Differential
    • Bacterial infection
      • green or black discoloration may indicate Pseudomonas aeruginosa infection
    • Psoriasis
    • Trauma
  • Treatment
    • Medical
      • topical therapy
        • indications
          • when there is < 80% nail involvement and no involvement of the lunula
        • drugs
          • efinaconazole 10%
          • tavaborole 5%
      • oral therapy
        • indications
          • involvement of lunula
          • proximal subungual onychomycosis
          • lack of response to topical therapy
          • Candida onychomycosis
        • drugs
          • terbinafine
            • for dermatophytes
          • itraconazole
            • for dermatophytes and Candida spp.
    • Operative
      • nail avulsion
        • indication
          • severe onycholysis, thickening, or dermatophytomas
  • Complications
    • Secondary bacterial infection
  • Prognosis
    • High rates of recurrence
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