ONYCHOMYCOSIS: A Fungus Among Us

Onychomycosis is the medical term for the invasion or infection of the nail, either toenail or fingernail, by a fungus. Fingernail infections may be particularly embarrassing but are less common than infections of the toenails. Many of the risk factors and treatments are identical for both types of nail infections, but this article will focus on infections of the toenails, a very common problem which affects 6-8% of the population.

Fungal infections of the toenails are often seen in conjunction with athlete’s foot, a fungal infection of the skin of the foot typically caused by walking around in moist public places like swimming pools, locker rooms or public showers. Other risk factors include sharing the shoes of an infected person or wearing shoes that do not allow for good air circulation around the feet. People with diabetes, poor blood circulation in the feet, a weakened immune system, older age, and contact with people who have the disease are also at increased risk.

Fungal toenail infections are characterized by thickening or flaking of the toenail and a change in color to white or yellowish-brown. Sometimes the nail can detach from the nail bed. Onychomycosis is typically painless but can lead to a bad smell or pain, especially when walking. Without treatment, the infection may persist indefinitely.

If your doctor suspects that you have onychomycosis, he or she may obtain a sample of the discolored area of the nail in order to distinguish the infection from other causes of a discolored nail, including psoriasis, contact dermatitis, or injury. By looking at this sample under the microscope or sending it to a lab for culture, your doctor can determine whether the characteristic fungi are present.

Treatment of nail fungal infections is difficult because of the potential side effects and poor success rates of the available medications, and the long courses of treatment required to achieve a cure. Some of the factors which make treatment particularly challenging include the long period that the nail takes to grow, the hardness of the toenail, and the difficulty of actually getting a medication to the infected area under the toenail, either through the bloodstream or by direct application.

Lamisil (terbinafine) is one of the best-known and most successful methods of treatment. For fungal infections of the toenail, it is given once a day for twelve weeks. The medication continues to work in the nail bed for several months after you stop taking the pills and it may require 9-12 months before the full effect of the medication is appreciated. Approximately three-quarters of patients achieve success with Lamisil. Lamisil can occasionally lead to liver disease, and so your doctor will obtain periodic blood tests during the course of treatment to monitor liver function.

Sporanox (itraconazole) tablets may also be used over a twelve-week period. This has a lower cure rate (approximately 60%) than Lamisil but is more effective against onychomycosis caused by yeast and has a lower, although still present, risk of liver damage. Both Lamisil and Sporanox have many potentially dangerous interactions with other medications, so it is important that your doctor has an up-to-date list of all prescription and over-the-counter medications you are taking.

An alternative treatment is Penlac (ciclopirox), which is an antifungal nail polish or lacquer that is applied once a day. Although this treatment is rarely effective, with only 7 percent of patients who actually achieve relief, it has no side effects or risk of liver damage and no interactions with other medications. It may be an option for some patients. Finally, surgical therapy involving complete removal of the nail is a possibility in occasional cases.

Unfortunately, each of these treatment options carries a high risk of recurrence, approximately 20-50 percent. Sometimes recurrence rates are minimized by continuing to take antifungal medications like Lamisil or Sporanox intermittently or applying antifungal creams or Penlac.

Dr. McMahon, a graduate of Yale University and the University of Pittsburgh School of Medicine, is board certified in Internal Medicine. She is a member of the American College of Physicians and the Allegheny County and Pennsylvania Medical Societies. She is in solo practice in the North Hills of Pittsburgh.