Tinea Unguium (Onychomycosis)

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

Diagnosis

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

Treatment

Medications

• 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 ...