Tuesday, March 28, 2023
This educational activity is intended for dermatologists, podiatrists, and primary care physicians.
The goal of this activity is to update clinicians on the recognition and treatment of onychomycosis.
The College of Physicians and Surgeons of Columbia University is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.
The College of Physicians and Surgeons of Columbia University
designates this educational activity for a maximum of 2.0 category 1
credits toward the AMA Physician's Recognition Award. Each physician
should claim only those credits that he/she actually spent in the
educational activity.
Participants who have earned credit for the monograph titled
"Progression and Recurrence of Onychomycosis" published in March 2003
are not eligible for credit for this online activity.
For questions regarding the content of this activity, contact the accredited provider for this CME/CE activity noted above. For technical assistance, contact [email protected]
There are no fees for participating in or receiving credit for this
online educational activity. For information on applicability and
acceptance of continuing education credit for this activity, please
consult your professional licensing board.
This activity is designed to be completed within the time
designated on the title page; physicians should claim only those
credits that reflect the time actually spent in the activity. To
successfully earn credit, participants must complete the activity
online during the valid credit period that is noted on the title page.
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Onychomycosis is a progressive, recurring fungal infection that begins in the nail bed and progresses to the nail plate. Although superficial, fungal nail infections should be taken seriously because they can cause significant health problems: they are contagious -- a reservoir of fungal microorganisms is created that can be transmitted through shoes and direct contact.[1] Consequently, infection can spread from the feet (in toenail onychomycosis) to other areas of the body within an individual patient.[2] Infection can also be transmitted between susceptible individuals.[3]
Fungal nail infections increase the susceptibility of patients to other serious complications. In diabetic patients, onychomycosis can open the door to secondary bacterial infections promoting foot ulcers and gangrene.[1,4] Onychomycosis can also trigger recurrent cellulitis and thrombophlebitis.[1,5] In addition to these significant health problems, the substantial psychosocial consequences of onychomycosis alone justify serious management.
Observations from a recent survey found that 92% of patients with onychomycosis reported experiencing negative psychosocial and/or physical effects.[6] Patient self-assessment surveys and observational studies indicate that 67% to 74% of patients are embarrassed by the condition of their nails as a result of onychomycosis.[7,8] A significant proportion of patients also experience pain (36% to 48%) or limited mobility (41%) resulting from onychomycosis.[7-9] This disease may also reduce self-image and self-esteem.[6,9] Importantly, quality-of-life scores have been shown to correlate significantly with the duration and severity of mycosis and the number of nails involved, observations that support early and aggressive management.[10] In summary, onychomycosis has a negative impact on quality of life.
Some physicians decline to treat onychomycosis, despite the negative consequences of this infection on patient health and quality of life. Physicians who feel it unnecessary to treat onychomycosis may regard the disease as a cosmetic problem rather than a health problem.[11] Physicians may also be concerned that the risk of systemic therapy may outweigh the benefits. Attitudes toward onychomycosis need reexamination because the number of patients who are susceptible to this disease is substantially increasing. To manage these patients effectively, physicians will need to understand the characteristics of the disease and adopt appropriate diagnostic, treatment, and preventive strategies.
Onychomycosis is not an uncommon disease. This type of infection has been estimated to be responsible for up to 50% of all nail diseases, and the incidence of onychomycosis is increasing.[9] Recent large scale studies indicate that the prevalence of onychomycosis is approximately 6.5% in Canada and nearly 14% in North America.[12,13] Individuals with certain conditions are more susceptible to fungal nail infections and, therefore, may have a higher prevalence of the disease than the general population. Predisposing characteristics to onychomycosis include the following:
The main structural components of the nail include the proximal and lateral folds, cuticle, matrix, plate, bed, and hyponychium (Figure 3).[22] The proximal nail fold is located at the proximal end of the visible nail plate where the skin folds over itself. The horny layer of the proximal nail fold is called the cuticle.
Several clinical variations of onychomycosis can develop: distal subungual, proximal subungual, white superficial, and endonyx. Distal subungual onychomycosis (DSO) is the most prevalent type of fungal nail infection, occurring in 75% to 85% of cases.[12] This variation of onychomycosis occurs between the distal underside of the nail plate and the nail bed, and is most often caused by the dermatophyte T rubrum.[12] Fungal pathogens enter the distal nail bed epidermis from the sole of the foot and toe webs through the hyponychium or the lateral nail fold.[26] In fact, most cases of onychomycosis are associated with dermatophyte infection of the feet (tinea pedis).[27]
Clinical observations clearly indicate that the risk of developing onychomycosis increases substantially with age.[12] This correlation deserves considerable attention by physicians who practice in managed care settings, because the managed care population contains a disproportionate number of geriatric patients, who have a high risk of developing chronic degenerative diseases (ie, diabetes and peripheral vascular disease) that predispose them to fungal nail infections.[14,16,32-34]
US veterans can be considered to be an example of a managed care population with a high risk of onychomycosis. Although the total number of US veterans decreased by 4% during the period from 1990 to 2000, the number of veterans over the age of 65 years increased from 7.2 million in 1990 to 9.9 million in 2001.[35,36] Similarly, the number of veterans over the age of 85 years increased from 154,000 in 1990 to 590,000 in 2001.[35,36] The growing number of geriatric veterans is reflected in the general US population. For example, the number of individuals over the age of 65 years has increased 12% during the period from 1990 to 2000 in the United States.[37] During this same time period, the number of individuals over the age of 85 years has increased 37%.[37] As the number of geriatric patients rises, physicians can expect to treat more patients with conditions that predispose them to fungal nail infections, such as diabetes and peripheral vascular disease. Indeed, a recent study by the Centers for Disease Control and Prevention found that the prevalence of diabetes increased from 4.9% in 1990 to 6.5% in 1998 -- an increase of 33%.[38]
Since the geriatric population is steadily increasing in managed care, and in the United States as a whole, the prevalence of onychomycosis in these populations is also likely to increase. This is an important consideration for physicians because fungal nail infections in older patients who are ill can cause limb-threatening complications, such as pressure necrosis of the nail bed and secondary bacterial infections.[17]
The frequency of recurrence of onychomycosis varies among patients, probably because of varying levels of susceptibility. Although the overall rate of recurrence is not known, recurrence rates between 6.5% and 53% have been reported, despite successful treatment with oral antifungal drugs.[20,21,39] However, the actual recurrence rate of fungal nail infections may be more than 10% higher because clinical trial populations are usually not representative of those encountered in clinical practice.[40] Therefore, when managing onychomycosis, physicians need to include preventive strategies to reduce the frequency and severity of recurring episodes.
Onychomycosis in many patients should be considered a controllable disease rather than a permanently curable disease. Controlling the recurrence of onychomycosis involves pharmacologic treatment and patient education. Patients will usually require follow-up treatment with a topical antifungal agent after the initial episode has been successfully cleared. Since treatment will be administered indefinitely, physicians should take into account potential long-term adverse effects and drug-drug interactions of the available oral medications when designing a preventive treatment strategy. In addition, patients presenting with both onychomycosis and tinea pedis will also require an antifungal medication to resolve the tinea pedis. Treating tinea pedis is important for preventing recurrence of onychomycosis, because the fungal pathogens infecting the skin may act as a reservoir for reinfection of the nail.
Patient education is just as important as pharmacologic therapy for controlling the recurrence of onychomycosis. Physicians need to explain to their patients about the chronic, infectious, and serious nature of the disease. Patients must also understand that they will need to take an active role in preventing future episodes of infection. Simple and effective patient strategies to prevent reinfection are listed below. Patients should be encouraged by their health care professional to follow these strategies.
The clinical diagnosis of onychomycosis is quite accurate, but laboratory confirmation is always needed to avoid incorrect diagnosis, as well as unnecessary exposure to antifungal medication. Laboratory confirmation is often required to receive reimbursement from managed care organizations. Although the presence of dystrophic nails with yellow to brown discoloration, onycholysis, and subungual hyperkeratosis makes onychomycosis the probable cause, physicians should resist the temptation to begin treatment empirically because psoriatic nail disease, eczematous dermatitis, and lichen planus can cause nail abnormalities that resemble onychomycosis.
Several laboratory techniques are available to physicians for confirming the clinical diagnosis of onychomycosis. These methods include potassium hydroxide (KOH) wet mount, fungal culture, and nail histopathology.
Specimen collection. Proper technique for specimen collection is critical for successful diagnosis. The specimen should be collected from the affected portion of the nail bed. Nails should be scraped or clipped near the bed, where new growth of the fungus is most likely to occur (Figure 6).
Fungal nail infections are among the most difficult superficial mycotic infections to treat effectively. Therapeutic strategies for onychomycosis vary among patients and are influenced by the severity of the disease.[27] Treatment approaches can be categorized into 4 groups: mechanical debridement, removal of the affected nail (nail avulsion), oral antifungal therapy, and topical antifungal therapy. The likelihood of recurrence is significant with any single approach; combining 2 or more approaches has the potential to maximize therapeutic efficacy and reduce recurrence.
Mechanical debridement is a traditional podiatric approach to onychomycosis that requires time, specialized instruments, and experience. The goal of this approach is to reduce pressure and fungal load by mechanically reducing nail thickness. Since mechanical debridement removes a large portion of onychomycotic material, it has the potential to enhance the effectiveness of other therapies, especially those involving antifungal medication. However, this approach does have limitations. For example, it does not eradicate the infectious pathogens, and it must be repeated as the nail grows until the infection has been resolved.
Nail avulsion involves removal of the affected nail plate, which can be performed either surgically or chemically using 40% urea, 30% salicylic acid, or 50% potassium iodide. This approach allows growth of a new nail but can traumatize the nail bed, which may affect the appearance of the new nail. Also, total nail avulsion causes discomfort to the patient, and therefore is discouraged.
Oral antifungal medications are often prescribed as first-line treatments for onychomycosis. These systemic drugs, terbinafine, itraconazole, and fluconazole (not FDA approved for nails), reach the infected nail via the peripheral circulation. The latest generation of oral antifungal medications have been shown to be effective in clinical studies.[45,46] For some of these newer oral antifungals, treatment periods have been reduced and intermittent or pulse dosing regimens have been prescribed to minimize adverse effects and cost. The reason for reducing the treatment period is that the newer drugs can remain in the nails for up to 6 months after treatment has ended.[47] However, it is important that physicians not underestimate the chronic nature of the disease. Despite the fact that oral antifungal medications have greatly improved over the past 10 years, it has been suggested that as many as 25% to 40% of onychomycosis cases are classified as treatment failures in clinical practice.[40]
Before prescribing oral antifungal medications, physicians should consider the potential for adverse effects with each patient. Certain oral antifungal drugs may affect liver function, cause neutropenia and transient taste disturbances, and can be involved in drug-drug interactions.[48,49,55] Therefore, liver function and white cell counts should be assessed at baseline and periodically during treatment. In addition, the financial impact of therapy should be considered with each patient, since the newer oral antifungal drugs are expensive.[50]
Clinical observations indicate that topical antifungal therapy is effective for the treatment of onychomycosis in some cases.[51] This approach involves the direct application of an antifungal drug to the infected nail. These drugs are thought to diffuse through the nail plate to reach the site of infection, where they then eradicate the fungal organisms.[52] Topical antifungal therapy is generally considered safe, with adverse reactions being mild and localized to the site of application. Adverse events reported include primarily erythema and, less frequently, swelling or a burning/tingling sensation at the application site.[51] Minimizing the treatment period of topical antifungal agents has not been a major concern in patients with onychomycosis because these drugs may not be as expensive as oral antifungals[50] and have few adverse effects.
The treatment periods for antifungal drugs vary from 3 months for oral and up to 12 months for topical. However, these times may vary depending upon the type and extent of infections .[51] In addition, the effectiveness of treatment is sometimes not visibly apparent for several weeks or months into therapy. As a consequence, it may be difficult for a physician to determine whether a particular antifungal treatment is efficacious. A physician may wish to consider waiting 2 months after the end of therapy. If clearing slows during this period, administration of another regimen of therapy is warranted. However, the diagnosis and the prescribed treatment should be re-evaluated if no clearing is apparent after 3 or 4 months of therapy.
Given the resilient nature of the pathogens in onychomycosis, physicians should consider combining more than one therapeutic approach for managing fungal nail infections, though combination therapy is not specifically approved in any product's labeling. For example, combining oral and topical antifungal medications may allow complementary drug penetration at the infection site (Figure 10).
Physicians today are faced with a rising number of patients who are susceptible to onychomycosis. For example, the number of individuals over the age of 65 years and the number of individuals with diabetes are steadily increasing. In addition, the number of persons living with acquired immunodeficiency syndrome has increased as deaths have declined over the past decade.[54] As these specific patient populations increase, the incidence of fungal nail infections is likely to rise as well. Therefore, physicians should consider preparing effective diagnostic, treatment, and preventive strategies that would efficiently manage onychomycosis for a growing patient cohort.
The successful management of onychomycosis begins with an appreciation of its characteristics. Physicians must understand that onychomycosis is a potentially serious, superficial, and progressive infection. This involves adopting a specific viewpoint: fungal nail infections are a recurring medical problem that should be treated. Once this is accepted, the best approach to management includes ongoing pharmacologic treatment and patient awareness. Preventive medication is necessary to control the disease after the initial episode is resolved. A drug with few adverse effects is preferred, such as a topical antifungal agent, since the medication may need to be taken indefinitely. In addition, it is vital that physicians also treat tinea pedis at the initial onset of onychomycosis and continuously thereafter, because the skin is the likely source of the pathogens that infect the nail.
Patient education is another key component to reducing the frequency and severity of fungal nail infections. Physicians need to communicate the potentially serious and recurring nature of the disease to patients -- that onychomycosis is an infection and that preventive strategies on the part of the patient are necessary to reduce recurrence. A strategic plan involving aggressive treatment, patient education, and continuous preventive medication for fungal nail and skin infections will provide patients with the best chance of successful disease control.
