Unsightly But Not Painful

DISCUSSION
Onychomycosis, also known as tinea unguium, is an extremely common problem, affecting approximately 10% of adults in the US (but only 4% to 6% in Canada). Common as it is, onychomycosis is also vastly overdiagnosed and frequently mistreated, as illustrated by this particular case. This combination creates confusion among patients and clinicians alike.

Several different organisms can cause what we call onychomycosis, but the most common is Trichophyton rubrum, a dermatophytic fungus also responsible for most cases of “athlete’s foot” and “jock itch.” The changes seen in onychomycotic toenails include yellow to brown discoloration, thickening, and often, brittle ends of the nail plates. Unfortunately, other diseases—including but not limited to psoriasis and lichen planus—can cause similar changes.

In this case, the classical appearance of the patient’s toenails, along with the athlete’s foot and involvement of the big toenails, made this a relatively easy diagnosis. In other circumstances, confirmation could have been provided from a simple nail clipping. Sent for pathologic examination, it would have exhibited signs of fungal organisms.

Even with a firm diagnosis, successful treatment is problematic. This man’s employment and choice of footwear—along with a family history that was revealed through further questioning—all conspire against him. Ideal treatment would eventuate in a cure, but with these factors against him, it is unlikely.

For example, a four-month course of the best treatment (terbinafine 250 mg/d), would probably clear his nails. However, the chance of recurrence would be at least 50%, for two reasons. One: His environment and heredity would leave him no less susceptible than before. Two: Continual or repeat exposure to this ubiquitous organism is almost certain.

If his toenails cleared, he could simply continue his use of oral terbinafine (taking 250 mg once or twice a week) in hopes of maintaining that state. This would constitute an off-label use of that drug, since there have been no studies of its effectiveness or safety with ongoing use. This “prevention” strategy has been tried with some success, however.

The good news? First of all, the patient’s wife of 20 years has shown no signs of developing onychomycosis and is unlikely ever to do so. It appears that women are not as susceptible as men, either by virtue of less perspiration, circumstance of career, or choice of footwear. And furthermore, onychomycosis is not an infection in any sense that we typically use that word. It almost never causes pain or even redness, except in association with nail dystrophy so severe that the nail plate cuts into adjacent live tissue.

TAKE-HOME LEARNING POINTS
• Onychomycosis is extremely common, affecting about 10% of adults in this country.

• Heredity and environmental factors play significant roles in a person’s susceptibility to onychomycosis.

• Men are far more likely to experience onychomycosis than women. 

• Surgical removal of onychomycotic toenails is completely ineffective.

• Petroleum jelly, window-cleaning fluid, and tea tree oil have not proven effective in treating onychomycosis. 

• First and second toenails are usually the first to be affected by this condition, presumably as a result of trauma.