Foot and Ankle Surgery
Volume 14, Issue 1 , Pages 53-54, 2008

Commentary on: “Athletes Foot: When All Else Fails” by William C.R. Agunwa [Foot Ankle Surg. 12 (2006) 209–210]

North Staffordshire Hospital, Stoke-on-Trent, ST4 7PA, United Kingdom

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1. Definition and prevalence 

Fungal infection of the feet (also known as Athlete's foot and tinea pedis to the classically minded) is a common condition with a prevalence around the 10% mark. This figure is higher in a few at risk groups such as miners with shared pit-head baths, the inmates of institutions and the immunocompromised [1].

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2. Clinical 

Three main clinical appearances are generally recognised.

1.Interdigital, with itching, peeling, maceration and fissuring of the (usually lateral) toe webs. Here the fissuring is important as a portal of entry for bacterial infection.

2.Moccasin pattern with diffuse erythema and scaling affecting the whole of the soles and sometimes the feet's lateral aspects. The scaling is often maximal along plantar creases and may also show collarette patterning. This variety is most likely to be associated with toe nail infection and a similar (usually unilateral) involvement of the palms.

3.Vesicular infection, with a patch of erythema, scaling and vesiculation on either the soles or dorsa of the feet.

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3. Causation and differential diagnosis 

These causative organisms mainly belong to the dermatophyte group of fungi with Trichophyton rubrum accounting for about 60% of cases; Trichophyton mentagrophytes (var. interdigitale) 25%; Epidermophyton floccosum 10% and combinations of these 5% [2].

Yeasts such as Candida albicans, moulds such as Scytalidium dimidiatum, bacteria such as Corynebacterium minutissimum (producing erythrasma) and various Gram negative species, may all produce a picture clinically similar to especially interdigital dermatophyte infection.

In addition, involvement of the feet by non-infective dermatoses such as eczema and psoriasis can mimic all of the three clinical sub-groups.

Because of this, mycological confirmation of the clinical diagnosis is important. This may be in the form of microscopic identification of hyphae in a potash preparation of skin scrapings, or a positive culture.

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4. Treatment 

As in the treatment of many skin diseases the physician has the option of both topical and systemic therapy. Topical therapy with its negligible risk of systemic adverse reactions should generally be tried first.

A variety of vehicles are available for these topical preparations, namely creams, ointments, powders, solutions and sprays. A cream is generally the vehicle of choice as it will be less greasy than an ointment, better for absorption than a powder and less likely to be irritant than a solution or spray.

Of contemporary topical therapies the allylamine terbinafine (Lamisil) or the various azoles such as clotrimazole (Canestan), econazole (Pevaryl) and miconazole (Daktarin) are the best options. There is a good evidence to suggest that one week of terbinafine is slightly more effective than four weeks of clotrimazole [3] and presumably the other azoles also. Against this the azoles do have a broader spectrum of activity (against yeasts, moulds, erythrasma and other bacteria). This effectiveness, extending beyond the dermatophytes may often be beneficial.

Whitfield's ointment (compound benzoic acid ointment with 3% salicylic acid) remains in the formulary after a hundred years, and has a role in scaly moccasin pattern tinea in combination with systemic therapy.

Systemic therapy may be indicated by:

1.failure of topical treatment.

2.extensive infection as in moccasin pattern tinea.

3.concomitant toe nail or other more widespread involvement of the skin elsewhere.

Griseofulvin has been available for over fifty years but is less effective than oral terbinafine [4] and itraconazole [5]. There may not be much to choose between terbinafine 250mg o.d. and itraconazole 200mg o.d. in achieving cure in dermatophyte infections. Two to four weeks of therapy may be required for mycological cure. Two other factors may guide preference for one over the other. Firstly, itraconazole is subject to a far greater number of drug interactions; thus a patient's concomitant drug therapy may be important. Secondly itraconazole has the broader spectrum of activity and may thus be effective against moulds such as Exophiala werneckii (causing tinea nigra) Hendersonula toruloidea and Scytalidium hyalinum, whether these are lone pathogens or co-existing with dermatophytes.

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5. “When all else fails” 

Failure of the above treatments in athelete's foot is rare. There are a number of difficulties in evaluating the paper and subsequent correspondence by Agunwa, which relates to this situation.

1.Although, he refers to “many cases”, we are not told how many and are given the example of just one.

2.No results of mycological isolation are given. Ideally one would like to see positive cultures before treatment with their becoming negative afterwards.

3.This absence raises the possibility of the clinical picture here being due to non-fungal causes such as bacterial infection or an inflammatory dermatosis.

4.Baking powder is, as stated, a mixture of several substances, so one is left uncertain as to which of these may be the most important as an anti-fungal. One would concede that the status of tar (with ten thousand plus compounds) in dermatology might mitigate this criticism.

However, suggested new modalities are always interesting, not least when they make a step back to the era of inorganic compounds in therapy (circa 1450–1900).

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References 

  1. Torssander J, Karlsson A, Morfeld-Manson L, et al. Dermatophytosis and HIV infection: a study in homosexual men. Acta Derm Venereol. 1988;68(i):53–56
  2. de Vroey C. Epidermiology of ringworm (dermatophytosis). Semin Dermatol. 1985;4:185–200
  3. Elewski B, Hanifin J, et al. Topical terbinafine and clotrimazole in interdigital tinea pedis; a multicentre comparison of cure and relapse rates with one and four weeks treatment regimens. J Am Acad Dermatol. 1993;28:648–651
  4. Savin RC. Oral terbinafine versus griseofulvin in patients with tinea pedis and tinea manus. NZ Med J. 1994;107:126–128
  5. Agunwa WCR. Athlete's foot: when all else fails! Foot Ankle Surg; 2006.

PII: S1268-7731(08)00003-9

doi:10.1016/j.fas.2008.01.002

Foot and Ankle Surgery
Volume 14, Issue 1 , Pages 53-54, 2008

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