Tinea Unguium (Onychomycosis)

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About tinea unguium (onychomycosis)

Tinea unguium, also known as onychomycosis, is infection of the nail—usually the distal nail bed—with a dermatophytic fungus. The usual culprits are Tricophyton rubrum and Tricophyton mentagrophytes, with T. rubrum being the most common cause of distal subungual onychomycosis. The nail appears discolored with areas of yellowish-brown or white. Involvement of the nail undersurface results in debris buildup and nail separation. Infection of the top surface leads to a brittle white surface. Involvement of the proximal nail plate is a sign of HIV infection.

Tinea unguium is a common problem, with prevalence increasing with age. The toenails are affected more frequently that the fingernails. The most common complaint is regarding the thickened unsightly appearance of the nail, but the condition can also cause pain or discomfort.

Onychomycosis is classified clinically into several categories: distal and lateral subungual onychomycosis (DLSO), superficial white onychomycosis (SWO), proximal subungual onychomycosis (PSO), candidal onychomycosis and total dystrophic onychomycosis.

With what can tinea unguium (onychomycosis) be confused?

Nail disease is difficult to diagnose by appearance alone. The nail plate appearance of tinea unguium can be confused with the changes caused by psoriasis, trauma, or aging. Psoriasis will usually have other skin findings, and trauma can usually be identified by history. Furthermore, nail disease of other causes, such as trauma, can be come secondarily infected with yeast, dermatophytes or saprophytes.

How is tinea unguium diagnosed?

A KOH preparation and fungal culture or a nail clipping confirms the diagnosis (though KOH preps are rarely done today in most offices.)

How is tinea unguium treated?

As is the case for tinea capitis, fungal infection of the nail often cannot be eradicated with topical therapy; oral anti-fungal agents such as terbinafine (e.g. Lamisil) or itraconazole (e.g. Sporanox) are required for weeks to months, during which time the drug accumulates in the nail. Pulsed therapy is sometimes used, treating one week per month for several months. Grisofulvin can also be used, especially in children, but is not the treatment of choice in adults. Systemic antifungal agents have side-effects and the risk-benefit must be considered. Monitoring of hepatic enzymes and hematologic parameters is recommended. Since these drugs remain in the nail for months, retreatment should not be considered for six months for fingernails and 12 months for toenails.  More recently, some have proposed laser treatment as an option, and the Nd:YAG laser may be effective for this. Newer topical agents Jublia and Kerydin have shown efficacy as well. Stubborn nail fungus can also be treated with laser for nail fungus.

What is the prognosis for tinea unguium?

After a course of treatment, nails will still not appear completely normal. Onychomycosis is difficult to cure, and recurrence is common, especially for toenails.

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