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Onychomycosis

OB/GYN News, Nov 1, 2004 by Michele G. Sullivan

Onychomycosis--fungal infection of the toenails or fingernails--is a common problem, affecting up to 25% of the population. The most common infective organisms--Trichophyton mentagrophytes and Trichophyton rubrum--are dermatophytes commonly present in soil and on human skin. These microorganisms usually get a toehold when a nail is damaged in some way. The trauma can be caused by something as inconspicuous as a tight-fitting shoe that puts constant pressure on a nail or the end of a toe. Of all fungal nail infections, about 80% are of the big toenail and 20% are of the fingernails.

Diagnosis

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The daily environment for most feet--the dark, moist warmth of socks or stockings in shoes--is the perfect habitat for fungal growth. Women who make frequent visits to the gym or pool may be at increased risk for these infections, as their feet are even more exposed to moisture and warmth. Pregnant women, whose feet change shape because of edema or ligamentous laxity, should be counseled to change shoe sizes or types as these changes occur. This may help prevent nail trauma that can predispose them to onychomycosis.

Women with chronic diseases such as diabetes, circulatory problems, or immune deficiency conditions are especially prone to fungal nail infections. Other contributory factors may be a history of athlete's foot and excessive perspiration. The first symptom is a change in nail color, usually yellow streaks in the nail bed and beneath the nail. Later, the nail may become brittle or crumbly, lose its luster, thicken, or become dystrophic. Debris may be present under the nail, which eventually may become loose or even detach. The toes may be malodorous and the skin around the nail may become inflamed.

Management

A culture is usually recommended to identify the infective organism. Yeasts and molds can also be causative agents.

Because the toenails grow so slowly, it will take months--even up to 1 year--to see complete clearance of symptoms with any drug therapy Sometimes, even with mycologic cure, the nail will remain deformed. If the entire plate has been affected, the fungus has probably invaded the nail bed; this may have damaged the nail matrix, resulting in permanently dystrophic nails.

The usual treatment is a course of oral antifungal medication. Terbinafine is the most commonly prescribed drug. The usual dosage is 250 mg/day for 90 days for toenail infections and 250 mg/day for 6 weeks for fingernail infections.

Terbinafine has been associated with serious hepatic dysfunction: Fatalities have occurred, although most have been in patients with preexisting liver disease. Liver function should be assessed before use and after 4-6 weeks. The drug should not be prescribed to patients with liver or renal dysfunction.

Itraconazole is also effective. The recommended dosage for toenails, with or without fingernail involvement, is 200 mg/day for 12 consecutive weeks. For fingernails only, the dosage is two treatment pulses of 200 mg twice a day for 1 week. The pulses should be separated by a 3-week period without the drug.

Itraconazole should not be prescribed for anyone with evidence of a ventricular dysfunction, including a history of or current congestive heart failure, and should be immediately discontinued if signs of congestive heart failure occur during use. Itraconazole should not be prescribed to patients who are taking cisapride, pimozide, quinidine, dofetilide or levacetylmethadol. Coadministration can cause increased plasma concentrations of these drugs, leading to serious cardiovascular events.

Neither terbinafine nor itraconazole should be prescribed to women who are pregnant or breast-feeding. These women should receive ciclopirox 8% solution, a topical antifungal lacquer that must be applied daily for up to 48 weeks. A podiatrist should manage patients with diabetes who develop onychomycosis of the toenails.

Prevention

Patients should be advised to keep their feet clean and dry. Applying a little talcum powder between the toes and on the feet before putting on socks or stockings is a good idea. Some of the newer sock fabrics wick moisture away from the feet and could be a good investment for patients prone to fungal nails.

Women who enjoy pedicures should be vigiland about their choice of salon and make sure employees follow rigorous sanitary procedures. Footbaths and instruments should be sterilized after every customer. Tell your patients to clip their toenails straight across, and never to dig into the sides of the nail. Sometimes, fungal nails become so thickened they're impossible to cut with small clippers. These women should see a podiatrist for regular foot care.

Sources: Robert Russo, D.P.M., Rochester, N.Y.; American Podiatric Medical Association

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Onychomycosis

OB/GYN News, Nov 1, 2004 by Michele G. Sullivan

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