A 34-year-old woman presents with an itching rash on both feet for the past 6 months (Figure 146-1). She is in otherwise good health and has occasionally tried some over-the-counter (OTC) athlete's foot medicine for this rash with slight improvement. On physical exam, the patient has erythema and scale in the moccasin distribution as well as some of her interdigital spaces. A KOH preparation is positive for branching hyphae with visible nuclei enhanced by the Schwartz Lamkins stain (Figure 146-2). Patient denies a history of hepatitis or heavy alcohol use and would like to try an oral medication because she is tired of the itching. The patient is given oral terbinafine 250 mg daily for 2 weeks.
Tinea pedis in the moccasin and interdigital distribution. (Reproduced with permission from Richard P. Usatine, MD.)
Microscopic view of the KOH preparation showing branching hyphae with nuclei that are easy to see under 40× power with Swartz Lamkins stain. (Reproduced with permission from Richard P. Usatine, MD.)
Tinea pedis is a common cutaneous infection of the feet caused by dermatophyte fungus. The clinical manifestation presents in 1 of 3 major patterns: interdigital, moccasin, and inflammatory/vesicular. Concurrent fungal infection of the nails (onychomycosis) occurs frequently.
Tinea pedis is the most common human dermatophytosis.1
70% of the population will be infected with tinea pedis at some time.1
Prevalence increases with age and it is less common before adolescence.1
ETIOLOGY AND PATHOPHYSIOLOGY
A cutaneous fungal infection most commonly caused by Trichophyton rubrum.1
Trichophyton mentagrophytes and Epidermophyton floccosum follow in that order.
T. rubrum causes most tinea pedis and onychomycosis.
Use of public showers, baths or pools—especially if protective footwear is not used.2
Household member with tinea pedis infection.2
Certain occupations (miners, farmers, soldiers, meat factory workers)—especially where there is use of heavy boots and the feet are warm and sweaty.2
Persons experiencing homelessness.3
TYPICAL DISTRIBUTION AND MORPHOLOGY
Three types of tinea pedis:
Tinea pedis seen in the interdigital space between the fourth and fifth digits. This is the most common area to see tinea pedis. (Reproduced with permission from Richard P. Usatine, MD.)
Tinea pedis in the moccasin distribution. (Reproduced with permission from Richard P. Usatine, MD.)
Vesiculobullous tinea pedis with bullae present. This is an inflammatory reaction to the tinea pedis. (Reproduced with permission from Richard P. Usatine, MD.)
Vesiculobullous tinea pedis with vesicles and bullae over the arch region of the foot. The arch is a typical location for vesiculobullous tinea pedis. (Reproduced with permission from Richard P. Usatine, MD.)
However, many persons have both the interdigital and moccasin type simultaneously, as seen in Figure 146-1. In one prospective study of 135 patients presenting consecutively with tinea pedis, lesions were suggestive of the intertriginous type in 24 patients, moccasin type in 50 patients, and both intertriginous and moccasin type in 58 patients. Among the remaining patients, 1 had the vesiculobullous type and another had both the vesiculobullous and intertriginous types.4
In another larger study of 1174 persons, 674 had only interdigital tinea pedis while 500 subjects had a moccasin distribution in addition to the interdigital presentation.5
Some authors describe an ulcerative type (Figure 146-7).
Ulcerative tinea pedis with spreading vesicles related to a bacterial superinfection. The patient was treated with antifungals and antibiotics. (Reproduced with permission from Richard P. Usatine, MD.)
Interdigital—white or green fungal growth between toes with erythema, maceration, cracks, and fissures—especially between fourth and fifth digits (see Figure 146-3). The dry type has more scale, and the moist type becomes macerated.
Moccasin—scale on sides and soles of feet (see Figures 146-1 and 146-4).
Vesiculobullous—vesicles and bullae on feet (see Figures 146-5 and 146-6).
Ulcerative tinea pedis is characterized by rapidly spreading vesiculopustular lesions, ulcers, and erosions, typically in the web spaces (see Figure 146-7). It is accompanied by a secondary bacterial infection. This can lead to cellulitis or lymphangitis. Tinea pedis is a proven risk factor for nonpurulent leg cellulitis.6
Examine nails for evidence of onychomycosis—fungal infections of nails may include subungual keratosis, yellow or white discolorations, dysmorphic nails (Chapter 201, Onychomycosis).
Autoeczematization (dermatophytid reaction; Id reaction) is an uncommon hypersensitivity response to a fungal infection causing papules on the skin (Figure 146-8).
The hand shows an autoeczematization reaction to the inflammatory tinea pedis in the Figure 146-5. The vesicles between the fingers are typical of an autoeczematization reaction, also known as an Id reaction. (Reproduced with permission from Richard P. Usatine, MD.)
Between the toes, on the soles, and lateral aspects of the feet.
The most rapid method to confirm a clinical diagnosis is the KOH preparation. The involved skin is scraped with side of the microscope slide or a scalpel onto another slide. The slide is then prepared with KOH or KOH and a fungal stain. The slide is examined for hyphal elements (video https://www.youtube.com/watch?v=LUwNQI_0BWU) (see Figure 146-2). One study showed that the use of two KOH preparations from different parts of the suspected tinea pedis provided a substantial increase in diagnostic sensitivity.4
In a patient with tinea incognito on his foot and lower leg, the topical steroid masked the symptoms while the tinea spread up his leg (Figure 146-9). It took a KOH preparation to demonstrate that this was tinea and not lupus to get the patient the antifungal treatment he needed.
Tinea incognito on the foot of a 63-year-old black man with lupus. He was given topical steroids that allowed this fungus to spread and thrive. (Reproduced with permission from Richard P. Usatine, MD.)
A fungal culture is sometimes needed if one does not have the microscope to do a KOH preparation or if the KOH prep is negative but fungus is still suspected. A fungal culture may take up to 2 weeks for an answer, but the lab can often provide a KOH result within 1–2 days from the same sample. Just scrape the suspected tinea into a sterile urine cup and send to the lab.
Erythrasma is a bacterial infection found in intertriginous areas. It may appear as maceration between the toes and be mistaken for tinea pedis or coexist with tinea pedis (see Figures 125-5 and 125-6). In a study of 182 patients with interdigital lesions in a podiatry clinic, 40% were diagnosed as having erythrasma.7 Look for coral red fluorescence with a Wood lamp to diagnose erythrasma between the toes. A KOH preparation is helpful to confirm tinea. Fortunately, topical miconazole can treat both erythrasma and interdigital tinea pedis simultaneously8 (see Chapter 125, Erythrasma).
Pitted keratolysis: well-demarcated pits or erosions in the sole of the foot caused by bacteria (Figure 146-10) (see Chapter 124, Pitted Keratolysis).
Contact dermatitis tends to be seen on the dorsum and sides of the foot (Figure 146-11) (Chapter 152, Contact Dermatitis).
Keratodermas: thickening of the soles of the feet that can be caused by a number of etiologies, including genetics and menopause (Figure 146-12). This condition may look like tinea pedis in the moccasin distribution.
Dyshidrotic eczema is characterized by scale and tapioca-like vesicles on the hands and feet (Figure 146-13) (Chapter 153, Hand Eczema).
Friction blisters: blisters on the feet of persons leading an active athletic lifestyle.
Psoriasis can mimic tinea pedis but will usually be present in other areas as well (Figure 146-14) (Chapter 158, Psoriasis). Especially on the palms if this is palmarplantar psoriasis.
Pitted keratolysis on the sole of the foot with some interdigital tinea pedis. The pits are caused by bacteria and if not treated with an antibiotic will not resolve. (Reproduced with permission from Richard P. Usatine, MD.)
Contact dermatitis to an allergen in tennis shoes with typical distribution that crosses the dorsum of the foot. (Reproduced with permission from Richard P. Usatine, MD.)
Keratoderma climactericum, which started when this woman entered menopause. (Reproduced with permission from Richard P. Usatine, MD.)
Dyshidrotic eczema on the foot showing tapioca vesicles with peeling of skin on the tip of the second toe. The patient also has typical tapioca vesicles between the fingers. (Reproduced with permission from Richard P. Usatine, MD.)
Plantar psoriasis in a patient with other areas of psoriasis also present. (Reproduced with permission from Richard P. Usatine, MD.)
See Table 146-1 for management of tinea pedis.
TABLE 146-1Management of Tinea Pedis ||Download (.pdf) TABLE 146-1 Management of Tinea Pedis
|Tinea Pedis Type ||Treatment for Mild Cases ||Treatment for Recalcitrant Cases ||SOR |
|Interdigital type ||Topical antifungal ||Another topical antifungal or an oral antifungal ||A |
|Moccasin type ||Topical antifungal ||Oral antifungal ||A |
|Vesiculobullous type ||Oral antifungal ||Oral antifungal ||A |
Systematic review of 70 trials of topical antifungals showed good evidence for efficacy compared to placebo for the following:
In one meta-analysis, topical terbinafine was found to be equally effective as other topical antifungals, but the average duration of treatment was shorter (1 week instead of 2 weeks).10 SORⒶ
Topical terbinafine is a great first-line choice for tinea pedis because of its affordable cost as an OTC cream. SORⒸ
The moccasin distribution is more challenging to treat topically. In one large study, Naftifine gel 2% (Rx only) and vehicle treatment were applied once daily for 2 weeks.5 Then at week 6, the cure rates in the naftifine arm vs. the vehicle were statistically higher for mycologic cure rate (65.8% vs. 7.8%), treatment effectiveness (51.4% vs 4.4%), and complete cure rate (19.2% vs. 0.9%) for moccasin-type tinea pedis.5 Note that mycologic cure is defined as a negative dermatophyte culture and KOH, treatment effectiveness is defined as mycologic cure and symptom severity scores of 0 or 1, and complete cure is defined as mycologic cure and symptoms severity scores of 0. While naftifine gel was much better than vehicle, the data demonstrate that there may be significant failure to cure this type of tinea pedis and one should then consider oral antifungal treatment.
Luliconazole cream has recently been FDA approved for interdigital tinea pedis. It requires a prescription, and one tube is over $400. There are currently no data to recommend it over the inexpensive OTC topical antifungals.
TABLE 146-2Topical Antifungal Medications ||Download (.pdf) TABLE 146-2 Topical Antifungal Medications
|Agent ||Formulation ||Frequency* ||Duration* (weeks) ||NNT† |
|Clotrimazole || |
|Twice daily ||2 to 4 ||2.9 |
|Econazole ||1% cream ||Twice daily ||2 to 4 ||2.6 |
|Ketoconazole ||2% cream ||Once daily ||2 to 4 ||No data available |
|Luliconazole ||1% cream ||Once daily ||2 ||No data available |
|Miconazole || |
|Twice daily ||2 to 4 ||2.8 (at 8 weeks) |
|Oxiconazole || |
|Once to twice daily ||2 to 4 ||2.9 |
|Sulconazole || |
|Once to twice daily ||2 to 4 ||2.5 |
|Naftifine || |
|Once to twice daily ||1 to 4 ||1.9 |
|Terbinafine || |
|Once to twice daily ||1 to 4 ||1.6 |
|Butenafine ||1% cream ||Once to twice daily ||1 to 4 ||1.9 |
|Ciclopirox || |
|Twice daily ||2 to 4 ||2.1 |
|Tolnaftate || |
|Twice daily ||4 ||3.6 (at 8 weeks) |
In a Cochrane systematic review of 15 trials involving 1438 participants, the evidence suggests that terbinafine is more effective than griseofulvin.11 SORⒶ
In the same review, terbinafine or itraconazole are more effective than no treatment.11 SORⒶ
No significant difference was detected between terbinafine and itraconazole, fluconazole and itraconazole, fluconazole and ketoconazole, or griseofulvin and ketoconazole, although the trials were generally small.11 SORⒶ
Terbinafine is the oral treatment of choice, as it is very affordable being on the $4 and $5 lists at many pharmacies. It is at least as effective as other oral agents and more effective than griseofulvin. It has no more side effects or precautions than other oral antifungal agents. The dosing is 250 mg PO daily for 2 weeks. Avoid use if there is hepatic impairment, absolute neutrophil count (ANC) <1000, or creatinine clearance less than 50.
Patients with onychomycosis may have recurrences of the skin infection related to the fungus that remains in the nails and, therefore, may need oral treatment for 3 months to achieve better results.
Topical ammonium lactate (6% or 12%) and urea (10% to 40%) may be useful to decrease scaling in patients with hyperkeratotic soles in addition to treating their tinea pedis.
One small pilot study with 56 participants showed significant improvement or resolution of symptoms in patients treated by wearing socks containing copper-oxide fibers daily for a minimum of 8 to 10 days.12 SORⒷ
Do not go barefoot in public showers and locker rooms. Shower shoes may prevent tinea pedis. SORⒸ
Keep feet dry and clean, and use clean socks and shoes that allow the feet to get fresh air. SORⒸ
Use the topical antifungal medication again if recurrence occurs. SORⒸ
B. Updates on the epidemiology of dermatophyte infections. Mycopathologia.
TD, Van Zoost
C. Foot Conditions among homeless persons: a systematic review. PLoS One.
et al. Successive potassium hydroxide testing for improved diagnosis of tinea pedis. Cutis.
et al. Naftifine
hydrochloride gel 2%: an effective topical treatment for moccasin-type tinea pedis. J Drugs Dermatol.
et al. Risk factors for nonpurulent leg cellulitis: a systematic review and meta-analysis. Br J Dermatol.
MN. The prevalence of interdigital erythrasma: a prospective study from an outpatient clinic in Turkey. J Am Podiatr Med Assoc.
AG. A clinical double-blind trial of topical miconazole
against superficial fungal infections and erythrasma. Clin Exp Dermatol.
S. Topical treatments for fungal infections of the skin and nails of the foot. Cochrane Database Syst Rev. 2007;(3):CD001434.
R. Comparable efficacy and safety of various topical formulations of terbinafine
in tinea pedis irrespective of the treatment regimen: results of a meta-analysis. Am J Clin Dermatol
DJ. Oral treatments for fungal infections of the skin of the foot. Cochrane Database Syst Rev.
G. Treatment of tinea pedis with socks containing copper-oxide impregnated fibers. Foot (Edinb).