I recently had to remove some of a patient's toenails. Why on earth would someone want that done? Because they were infected with fungus. The medical term for a fungal infection of the toenails or fingernails is onychomycosis (OM).
This condition is generally more of a nuisance than a real health threat. However, infected nails can become quite enlarged and painful. Diabetics and people who have poor immune function need to be concerned about OM. Infected nails in these folks can lead to inflammation of the skin around the nails and entry of skin bacteria that can lead to serious skin infections.
Most people visit their doctors for OM because of the ugly nails. It is the most common nail disorder in adults and affects up to 13 percent of North Americans. It is 30 times more common in adults than children.
OM is caused by three types of fungi. The vast majority of these infections are caused by fungi that invade and feed on hair, skin and nails. These organisms are called dermatophytes and account for 90 percent of OM. Trichophyton rubrum (70 percent) and Trichophyton mentagropytes (20 percent) are the most common dermatophytes.
Yeasts and molds cause the remaining cases. It's often difficult to tell what organism is causing the infection without doing a culture in the lab which is usually recommended prior to starting treatment.
OM is a condition that we are seeing with increasing frequency. This is felt to be due to the large number of dermatophytes that arrived in North America by hitching a ride on people who have lived in or visited West Africa and Southeast Asia where the fungi thrive.
Risk factors for developing OM include a history of infection in the family, increasing age, poor health, trauma to the nail complex, warm moist climate and participation in fitness activities. Sharing shower facilities is a risk factor as is wearing shoes that do not allow adequate air circulation.
The fungi can invade the nail matrix, the nail bed, or the nail itself. There are actually up to five types of OM depending on what part of the nail complex is involved.
The most common type of OM starts when fungus from the bottom of the foot invades the underside of the nail at the outside corners where the nail grows over the end of the toe.
OM can have various appearances. The most common is characterized by a thickened nail plate that becomes opaque and may even become brownish in color. The nail becomes brittle and a white or yellow substance (keratin) may build up under the nail. Other types may simply present with a milky discoloration of the nail or just redness around the edge of the nail.
Treatment of OM can be very difficult. It is most effective if the exact organism can be identified along with determining what antifungal agents will kill it. Since there is no blood supply to the nail, medications take weeks to months to work as the diseased nail is replaced with treated, healthy nail tissue.
Topical treatment of OM usually only works for very mild cases involving less than half of the nail. Effectiveness is limited by the medication's ability to penetrate into the nail to kill the fungus. The most commonly used agent is cyclopirox (Penlac ®), though I'm sure you've seen the commercials for Jublia ®.
Oral antifungals are usually the most effective, either terbenafine (Lamisil) or itraconazole (Sporanox). These newer agents are more popular because of shorter treatment regimens (around 12 weeks), higher cure rates and fewer side effects. They can occasionally affect the liver, so it is important to obtain baseline blood work before treatment and to monitor liver tests every 4-6 weeks throughout treatment.
Mycologic cure rates (no evidence of fungal growth on culture) for oral medication varies from 25 to 50 percent depending on the study. Clinical cure rates (normal-appearing nails) may reach 75 percent. Fingernails typically do much better than toenails.
The recurrence rate of abnormal nails varies in different studies, but is about 20 percent three years after therapy. Factors that may lead to increased relapse rates include very thick nails, age, trauma, and disease on the outside edges of the nails.
If there is marked involvement of the nail, many physicians will also advise surgical removal of the infected nail. This helps speed recovery from the infection while taking oral medication. Following adequate treatment, it's important to note that the nail may take up to a year or so to look normal.
Dr. John Roberts is a local physician. His column appears in Monday's edition of the Times, and he has a daily health tip on the front page. Dr. Roberts is one of the owners of Sagamore News Media, parent company of The Times.