Nail fungus, medically known as onychomycosis, happens when fungi attack the nails. It is most common in toenails but can happen to fingernails as well. Fungal infections are more common in people with poor circulation of the feet (peripheral vascular disease) or diabetes.
The same fungi that cause athlete’s foot can also create nail fungus. The condition is sometimes called tinea unguium or ringworm of the nails.
Diagnosis
The most common fungal infections of the nails are caused by dermatophytes (60-70% of cases) and non-dermatophyte molds (20%). Onychomycosis is the clinical presentation of these infections. The condition primarily manifests as thickened and opaque nails that detract from the appearance of the nail bed and can obstruct normal activities.
The diagnosis of onychomycosis depends upon physical and microscopic examination and culture. The severity of the infection is defined by the number of visible spores per nail plate and the extent of the fungus involvement in the nail. In advanced cases of onychomycosis, the fungus spreads to the matrix of the nail and forms a dermatophytoma. This compact ball of spores and keratin has a striped or multicolor appearance in the nail plate. Other features of severe or long-standing onychomycosis include increased subungual hyperkeratosis, broader area of involvement of the nail and closer proximity to the matrix.
Potassium hydroxide (KOH) testing can confirm the presence of a fungal infection in the nail by demonstrating the discoloration of the nail plate. This test is easy and inexpensive to perform but does not provide the clinician with a specific identification of the pathogen (19).
Fungal cultures of the nail can identify the organism responsible for the infection; however, this requires the use of Sabouraoud dextrose agar which contains chloramphenicol and gentamicin to prevent contamination from bacteria and cycloheximide to inhibit the growth of newer antifungal drugs known as non-dermatophyte molds (NDMs) (18). Nucleic acid amplification tests offer an alternative approach to traditional diagnosis by directly identifying the pathogenic species using a sample of the affected nail. These tests are laboratory-developed and are regulated as high complexity tests under the Clinical Laboratory Improvement Amendments (CLIA).
Symptoms
Nail fungus (onychomycosis) is a fungal infection that can make your nails thick, discolored and brittle. It most often affects your toenails, but can also infect your fingernails. It can also lead to pain, discomfort and poor hygiene. It is more common in people with diabetes or poor circulation to the feet, and can spread from one person to another.
Most nail fungus is caused by a fungus called dermatophytes. But yeasts (such as Candida albicans) and nondermatophytic molds (such as Fusarium) can cause nail fungus, too. Fungal nail infections are more common in older people, especially men. They can be more difficult to treat than other types of nail infections.
Fungal nail infections usually start at the tip of a fingernail or toenail. As the infection goes deeper, the nail can become darker in color, crumble at the edge and separate from the skin around the nail. You may also notice that the nail is scaly or has white spots on it.
A doctor can diagnose nail fungus by looking at your nails. They may need to scrape off a small piece of your nail to perform a culture or a more precise test, such as periodic acid-Schiff staining or polymerase chain reaction. They can also suggest a treatment. Oral antifungal medicines, such as terbinafine (Lamisil) or itraconazole (Sporanox) can be taken every day for several months. They are most effective when used in combination with a topical treatment applied directly to the nails.
Treatment
A fungal infection of the nail unit, onychomycosis, can be cosmetically disfiguring and distressing to patients. It is caused by dermatophytes and nondermatophyte molds, with toenails affected far more frequently than fingernails. Symptoms include thickening and yellowing of the nails, accumulation of keratin debris under the nails (onycholysis), and detachment of the nail from the nail bed (onychomycolysis). It can also cause pain, sensitivity, and/or irritation.
Nail fungus is generally considered to be a benign condition and does not pose a risk to overall health, but it may impair quality of life. It is important to treat onychomycosis to prevent the progression of the disease, which results in worsening dystrophy and discoloration of the nail.
There are several FDA-approved topical, oral, and laser treatments for onychomycosis. However, many patients are unable to tolerate a long course of antifungal medication, and many do not achieve clinical or mycological cure after multiple treatment attempts. The selection of an appropriate treatment modality involves ethical considerations for patient and clinician. These factors may include cost, side effect profiles, adherence, and the extent to which a nail fungus is causing significant discomfort or impairment of daily activities.
When developing a treatment plan, dermatologists consider a patient’s overall health and medical history, any other medications they are taking, the type(s) of fungus causing the nail disease, and how much of each nail is affected. In addition, some dermatologists offer routine periodic thorough nail debridement to improve immediate patient satisfaction and increase the efficacy of oral antifungal medication.
Prevention
Although onychomycosis is not life threatening, it causes significant distress for patients due to its unsightly appearance. It may also limit mobility and indirectly decrease peripheral circulation, leading to complications such as venous stasis and diabetic foot ulcers [32]. It is therefore important for physicians to educate patients about the significance of this infection and to recognize the early signs of tinea unguium. This is to facilitate prompt recognition and treatment and thus to improve the chances of a successful outcome.
The success of treatment depends on both pharmacologic intervention and patient compliance. The use of current antifungal agents with high cure rates, short treatment durations, and intermittent dosing schedules significantly improves the odds of successful therapy. These newer agents are also safe and well tolerated. In contrast, older drugs (e.g., ketoconazole and griseofulvin) are less effective and frequently have adverse effects.
A successful diagnosis of onychomycosis requires a thorough history and physical examination, including the nails. The nail should be clipped short and a small curette or number-15 scalpel blade should be used to obtain a specimen from the infected area as close to the cuticle as possible. This should then be cultured for identification of the etiologic agent. Often, cultures identify more than one organism, so a consultation with a microbiologist or infectious disease specialist is helpful in interpretating the results and determining the appropriate course of action.