Fungus of the Feet and Nails
Tinea unguium, often referred to as onychomycosis, is an infection of nail tissue of the hands or the feet. T rubrum and Trichophyton interdigitale are the common dermatophytes known to cause tinea unguium. Nondermatophytes account for the remainder of infections, notably yeasts from Candida species, as well as molds from Fusarium and Acremonium species. Risk factors for onychomycosis include older age, swimming, trauma to the nail, diabetes, immunosuppression, living with someone with onychomycosis, and tinea pedis.
There are three forms of onychomycosis: distal subungual, superficial white, and proximal subungual. Distal subungual onychomycosis is the most common form, with the big toe usually the first nail to be affected. This form involves the end third of the nail farthest away from the cuticle and begins with a whitish, yellowish, or brownish discoloration of the nail. The discoloration eventually spreads to the entire nail and extends slowly to the cuticle. The discoloration is due in part to keratinous debris between the nail and the nail bed. A patient may present initially with hyperkeratosis of the nail bed, which may lead to onycholysis (separation of the nail from underlying tissue). Onycholysis causes pain, which may prevent the patient from being able to perform typical activities of daily living. Superficial white onychomycosis infects the entire top surface of the nail and has a flaky appearance. Proximal subungual onychomycosis, which is relatively rare, occurs mostly in immunocompromised patients; it presents with a seemingly deeper infection that occurs under the nail near the cuticle and extends distally. Unless treated properly, onychomycosis persists indefinitely.
It is important to recognize the presence of fungus before antifungal therapy is initiated. A variety of presentations exist that could lead to a differential diagnosis, including psoriasis, iron deficiency, eczematous conditions, trauma, yellow nail syndrome, periungual squamous cell carcinoma, and lichen planus. Studies have indicated that onychomycosis is responsible for only 50% to 60% of abnormal-appearing nails. The examiner must take into account the number of affected nails, as well as symmetry, pain, and other nail characteristics. Onychomycosis is most readily confirmed using a KOH preparation for histologic examination. Treatment should be initiated upon confirmation.
Topical and systemic therapies for onychomycosis exist; however, studies indicate that systemic therapies are more effective. Topical antifungal creams do not adequately penetrate the nail bed and are not considered appropriate. However, an antifungal topical in the form of a nail lacquer (e.g., ciclopirox) is an option, especially in patients in whom oral therapy is contraindicated. The combination of oral terbinafine and topical ciclopirox has not been shown to provide greater efficacy. Evidence supports the use of oral terbinafine or itraconazole for 6 to 8 weeks for fingernail onychomycosis. Toenail onychomycosis requires a longer duration of therapy (12–16 weeks for terbinafine, or continuous daily dosing with itraconazole for 12 weeks). In patients with onychomycosis, fluconazole 150 mg to 300 mg once weekly has been effective, but less effective than terbinafine or itraconazole. Griseofulvin, another treatment option, has been associated with lower clinical cure rates—as well as with recurrence—compared with terbinafine.Table 1 and Table 2 include a summary of available treatment options for onychomycosis.
Patients with onychomycosis should be educated about proper hygiene and lifestyle modifications in order to prevent relapse and recurrence. Patients should be encouraged to adequately trim the toenails directly across the toe with minimal curvature, as well as to avoid walking barefoot in damp areas. The feet should be kept clean and dry, and an emollient may be applied to areas of compromised dry skin where a fungal infection may be more probable. Adequate footwear that minimizes humidity should be worn, and should later be discarded upon significant wear and tear.
Tinea Unguium
Tinea unguium, often referred to as onychomycosis, is an infection of nail tissue of the hands or the feet. T rubrum and Trichophyton interdigitale are the common dermatophytes known to cause tinea unguium. Nondermatophytes account for the remainder of infections, notably yeasts from Candida species, as well as molds from Fusarium and Acremonium species. Risk factors for onychomycosis include older age, swimming, trauma to the nail, diabetes, immunosuppression, living with someone with onychomycosis, and tinea pedis.
There are three forms of onychomycosis: distal subungual, superficial white, and proximal subungual. Distal subungual onychomycosis is the most common form, with the big toe usually the first nail to be affected. This form involves the end third of the nail farthest away from the cuticle and begins with a whitish, yellowish, or brownish discoloration of the nail. The discoloration eventually spreads to the entire nail and extends slowly to the cuticle. The discoloration is due in part to keratinous debris between the nail and the nail bed. A patient may present initially with hyperkeratosis of the nail bed, which may lead to onycholysis (separation of the nail from underlying tissue). Onycholysis causes pain, which may prevent the patient from being able to perform typical activities of daily living. Superficial white onychomycosis infects the entire top surface of the nail and has a flaky appearance. Proximal subungual onychomycosis, which is relatively rare, occurs mostly in immunocompromised patients; it presents with a seemingly deeper infection that occurs under the nail near the cuticle and extends distally. Unless treated properly, onychomycosis persists indefinitely.
Treatment Strategies
It is important to recognize the presence of fungus before antifungal therapy is initiated. A variety of presentations exist that could lead to a differential diagnosis, including psoriasis, iron deficiency, eczematous conditions, trauma, yellow nail syndrome, periungual squamous cell carcinoma, and lichen planus. Studies have indicated that onychomycosis is responsible for only 50% to 60% of abnormal-appearing nails. The examiner must take into account the number of affected nails, as well as symmetry, pain, and other nail characteristics. Onychomycosis is most readily confirmed using a KOH preparation for histologic examination. Treatment should be initiated upon confirmation.
Topical and systemic therapies for onychomycosis exist; however, studies indicate that systemic therapies are more effective. Topical antifungal creams do not adequately penetrate the nail bed and are not considered appropriate. However, an antifungal topical in the form of a nail lacquer (e.g., ciclopirox) is an option, especially in patients in whom oral therapy is contraindicated. The combination of oral terbinafine and topical ciclopirox has not been shown to provide greater efficacy. Evidence supports the use of oral terbinafine or itraconazole for 6 to 8 weeks for fingernail onychomycosis. Toenail onychomycosis requires a longer duration of therapy (12–16 weeks for terbinafine, or continuous daily dosing with itraconazole for 12 weeks). In patients with onychomycosis, fluconazole 150 mg to 300 mg once weekly has been effective, but less effective than terbinafine or itraconazole. Griseofulvin, another treatment option, has been associated with lower clinical cure rates—as well as with recurrence—compared with terbinafine.Table 1 and Table 2 include a summary of available treatment options for onychomycosis.
Prevention Strategies
Patients with onychomycosis should be educated about proper hygiene and lifestyle modifications in order to prevent relapse and recurrence. Patients should be encouraged to adequately trim the toenails directly across the toe with minimal curvature, as well as to avoid walking barefoot in damp areas. The feet should be kept clean and dry, and an emollient may be applied to areas of compromised dry skin where a fungal infection may be more probable. Adequate footwear that minimizes humidity should be worn, and should later be discarded upon significant wear and tear.