Thickened, painful and yellow thumbnail

Onychomycosis, also known as tinea unguium, refers to a fungal infection of the nail. This very common condition accounts for 30% of all superficial fungal infections, and may involve the nail plate, nail bed or nail matrix.1 The organism Trichophyton...

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Onychomycosis, also known as tinea unguium, refers to a fungal infection of the nail. This very common condition accounts for 30% of all superficial fungal infections, and may involve the nail plate, nail bed or nail matrix.¹ The organism Trichophyton rubrum accounts for approximately 70% of cases and Trichophyton mentagrophytes accounts for approximately 20% of all cases; yeasts and nondermatophyte molds account for the remainder.² Overall, the toenails are affected at a significantly higher rate than are the fingernails.

There are four basic subtypes of onychomycosis. Distal subungual onychomycosis, the most common form, presents with yellow or white subungual hyperkeratosis, onycholysis and yellow streaking starting at the distal edge of the nail and progressing proximally. White superficial onychomycosis almost always affects the toenails only and presents with superficial white or milky patches and speckling on the nail plate.

Caution should be taken not to mistake this condition for keratin granulations, which has a similar appearance but is caused by frequent use of nail polish remover. Proximal subungual onychomycosis occurs when the fungus invades the newly forming nail plate, causing leukonychia that starts at the proximal nail plate and advances distally as the nail grows. This condition is most common in patients with immunosuppression.

Finally, candidal onychomycosis presents with marked periungual inflammation and is caused by a candida infection that is almost always secondary to a preexisting onycholysis.

The prevalence of onychomycosis in the adult population is between 6% and 8%.¹ Risk factors include immunosuppression, advancing age, humid environment, diabetes, peripheral vascular disease, communal bathing, and occlusive footwear.

Although onychomycosis is largely a cosmetic issue, a significant number of patients report intermittent pain and discomfort. Some develop periodic episodes of paronychia. In addition, there may be an increased risk of bacterial infection, particularly in persons with diabetes or a suppressed immune system.

Such other conditions as lichen planus, psoriasis, alopecia, Darier disease, allergic/irritant contact dermatitis, traumatic onycholysis, and yellow nail syndrome can also affect the nails and mimic onychomycosis.

When only one nail is affected, extreme caution must be used to rule out squamous cell carcinoma, malignant melanoma, or other tumors of the nail bed. Therefore, it is important to always confirm the diagnosis, using either direct microscopy with potassium hydroxide smear or fungal culture.

Treatment options for onychomycosis depend on the clinical subtype, the number of nails affected, and the patient’s health status. Some patients are asymptomatic and may not seek treatment, whereas others may request treatment largely for cosmetic purposes.

Topical therapy usually requires long-term administration, and the results are often disappointing. Systemic treatment is challenging because of the associated side effects and safety profiles. Surgical therapy is often painful and is therefore not well accepted.

Topical treatments include antifungals in cream form and in a nail-lacquer preparation. These options are typically only moderately effective, and often require months of consistent treatment. One study showed a cure rate of 29% to 36% after 48 weeks of treatment with ciclopirox 8% topical solution (Penlac Nail Lacquer).³ Although topical ciclopirox has an excellent safety profile and the cost is reasonable, a 48-week treatment period is unrealistic for most patients.

Oral terbinafine (Lamisil), itraconazole (Onmel, Sporanox), and fluconazole (Diflucan) have all been used for systemic treatment of onychomycosis. Terbinafine 250 mg/day for six weeks is indicated for treatment of the fingernails, and a 12-week course is indicated for treatment of the toenails.

Terbinafine is the most recent drug of choice for onychomycosis. Itraconazole is given as pulse dosing, 200 mg b.i.d. for one week out of every month for two to four months. In 2001, however, the FDA advised against prescribing itraconazole for treatment of onychomycosis in patients who have congestive heart failure (CHF) or a history of CHF.⁴ Prescribed less commonly, fluconazole is given once a week for six to 12 months.

Prior to the start of treatment, patients should be told that these medications have a success rate of approximately 80%.⁵ Patients should be screened to ensure they have no contraindications or potential for medication interactions. The FDA issued a warning regarding the potential for serious liver problems resulting from use of terbinafine and itraconazole.⁴

Clinicians must discuss with patients the risks and benefits of treatment. Although there do not appear to be any strong recommendations, some providers monitor liver function prior to and during treatment with these medications.

Laser treatment has recently emerged as another option for onychomycosis treatment. Because so little information is available regarding cure rates and recurrence rates, patients should be encouraged to consider the risks, benefits and side effects prior to initiating this costly option.

The patient in this case was counseled regarding the treatment options for onychomycosis. Topical treatment would require a significant time investment, whereas systemic treatments carried the potential for significant side effects. Surgical and laser treatment were ruled out. The patient decided to hold off on any treatment and elected to cover up the condition with nail polish. 

Esther Stern is a family nurse practitioner at Advanced Dermatology & Skin Surgery, P.C., in Lakewood, N.J.