Onychomycosis in Patients with Diabetes

Vol. 5 (6D) n June 2005 Although the published evidence is limited, patients with diabetes mellitus are more likely to develop onychomycosis than are patients without diabetes mellitus. A study conducted by Gupta et al showed that onychomycosis is 2.8 times more prevalent among people with diabetes mellitus than in those without the disease. Diabetic neuropathy can predispose a patient to develop onychomycosis and also can complicate the disease. Patients with diabetic neuropathy experience numbness in their feet. These patients cannot determine if their shoes are the correct size, thus tend to wear 1 to 2 sizes too small—the pressure from the small shoe activates the nerve endings, allowing them to feel their shoes. Onychomycosis causes thickening of the toenails, which can lead to serious bacterial infections and foot ulcerations. Along with the thickened toenails, the neuropathy creates the perfect environment for foot ulceration. A tight shoe causes trauma to the toenail and nail bed, and the neuropathy prevents the patient from experiencing the pain of the ulceration. Ulceration is the predisposing factor in up to 85% of lower extremity amputations. Foot ulceration occurs in approximately 19% of patients with diabetes mellitus. In those patients with foot ulceration, the prevalence of lower extremity amputation ranges from 6% to 43%, depending on the severity of the ulcer. More than 90 000 lower extremity amputations performed in the United States are caused by diabetes mellitus. The 5-year survival rate of a person with diabetes mellitus who has undergone a unilateral amputation is 39% to 68%. More recently, a study by Doyle et al showed an association among onychomycosis, ulceration, and gangrene. Patients with diabetes mellitus and with onychomycosis had a significantly higher rate of foot ulceration, gangrene, and a combination of foot ulcer and gangrene than did patients with diabetes without onychomycosis (Figure 1). Although these data do not prove that onychomycosis causes ulcerations and gangrene, they strongly suggest a positive association. In my experience, onychomycosis usually is present in an amputated lower limb. Onychomycosis presents as a spectrum of disease, ranging from mild to extremely severe and is an infection that should be treated as such because it can spread within a nail, across toes, or to other parts of the foot or body. Onychomycosis is a progressive infection that has serious consequences, thus it must be treated aggressively. The following are 5 cases that exemplify the sequelae of onychomycosis in a diabetic population.