Tinea Unguium (Onychomycosis)

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

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 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

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

  • Evidence suggests that efinaconazole 10% performs better than other 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, 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, 400 mg once weekly for 6 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

  • If terbinafine cannot be used, pulse oral itraconazole 200 mg twice daily for 1 week per month for 3 months is an inferior but acceptable alternative

  • Griseofulvin is not effective

Follow-Up

• Monitoring of liver enzymes and CBC is recommended monthly during terbinafine treatment

• Courses of terbinafine or itraconazole may need to be repeated 6 months after the first treatment cycle if fungal cultures of the nail are still positive

Prognosis

• Once clear, fingernails often remain free of disease for years

• About 75% of patients will have substantial improvement with systemic therapy, and 35–50% will be mycologically and clinically cured at 1 year

• Relapses are more common with itraconazole than terbinafine in toenail onychomycosis

When to Refer

• There is a question about the diagnosis

• Recommended therapy is ineffective

• Specialized treatment is necessary