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For further information, see CMDT Part 6-54: Nail Disorders

Key Features

Essentials of Diagnosis

  • A trichophyton infection of one or more fingernails or toenails

  • Yellowish discoloration with heaping of keratin

  • Separation of the nail bed

General Considerations

  • The species most commonly found is Trichophyton rubrum

  • "Saprophytic" fungi may rarely (< 5%) cause onychomycosis

  • Evidence supporting a genetic defect in the innate and adaptive immune system may explain why some people suffer from chronic tinea pedis and onychomycosis

Clinical Findings

Symptoms and Signs

  • The nails are lusterless, brittle, and hypertrophic

  • The substance of the nail is friable

Differential Diagnosis

  • Psoriasis

  • Candidal onychomycosis

  • Lichen planus

  • Allergy to nail polish or nail glue


Laboratory Tests

  • Laboratory diagnosis is mandatory since only 50% of dystrophic nails are due to dermatophytosis

  • Portions of the nail should be cleared with 10% KOH and examined under the microscope for hyphae

  • Fungi may also be cultured from debris collected from underneath the nailplate

  • Periodic acid-Schiff stain of a histologic section of the nail plate will also readily demonstrate the fungus



  • Difficult to treat because of the long duration of therapy required and the frequency of recurrences

  • Fingernails respond more readily than toenails

  • For toenails, treatment is indicated for patients with discomfort, inability to exercise, diabetes mellitus, and immune compromise

  • Topical therapy

    • Limited value historically

    • However, efinaconazole 10% has been approved as a topical therapy; evidence suggests that it performs better than prior topical treatment options

    • Tavaborole 5% solution is also approved, but its clearance rates do not appear to be as good as those of efinaconazole

  • Ketoconazole is not recommended to treat any form of onychomycosis

Systemic therapy

  • Is generally required for the treatment of nail onychomycosis; fingernails can virtually always be cleared, whereas toenails can be cured 35–50% of the time and improved in about 75% of cases

  • Fingernails

    • Ultramicrosize griseofulvin, 250 mg three times daily orally for 6 months, is often effective

    • Treatment alternatives, in order of preference, are terbinafine, 250 mg once daily orally for 6 weeks, itraconazole, 200–400 mg/day orally for 7 days each month for 2 months, and itraconazole, 200 mg/day orally for 2 months

    • Off-label use of fluconazole, 150–400 mg once weekly for 6–9 months, can also be effective, but there is limited evidence for this option

  • Toenails

    • Terbinafine, 250 mg once daily orally for 12 weeks, is best treatment

    • Pulse terbinafine therapy with 2 cycles of 4 weeks on and 4 weeks off may be as efficacious as continuous oral therapy

    • Itraconazole 200 mg daily for 12 weeks or ...

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