Tinea pedis - an occult disease?

On my blog, fungal infection is the most frequent topic but that’s because common things occur commonly. Fungal skin infections are amongst the top five diseases in the world today [1] and continues to rise [2]. Tinea pedis forms a significant subset of this and is certainly the most common infection we see in the podiatry clinic today. Studies have suggested around one third of European adults have the infection [3]. Untreated the condition can easily spread to the hands, groin, nails and occasionally elsewhere to other parts of the skin.

In addition, tinea pedis is a significant risk factor for the development of lower limb cellulitis [4] – a major cause of morbidity particularly in older patients or those with diabetes and/or reduced circulation. As it stands, we have a range of effective antifungal drugs, both oral and topical to treat and eradicate the fungal infection, yet it continues to be a significant problem. Why is this? There could be two reasons – either it is going unrecognised or ignored by the patient or healthcare professional, or it has been recognised but not sufficiently treated.

Tinea Pedis – not being recognised ?

Under recognition is an issue that has been discussed. For most people, the infection typically goes unnoticed and when we diagnose it in the clinic, patients often seem surprised. One study of randomly selected manual workers showed a high level (89%) of unrecognised tinea foot infection [5]. Another study undertaken at a meeting of patients with diabetes discovered an infection rate of 82% which was surprising as they were all motivated individuals attending a health conference. In addition, amongst this group 65% reported examining their feet daily and 41% regularly attended a chiropodist/podiatrist [6].

Tinea pedis for many is a very subtle infection with few symptoms.

Lack of self-examination of the foot, particularly in older adults, is something which we encounter with regard to disease recognition and melanoma where limited visualisation by the patient may contribute to decreased recognition [7] (see my earlier blog on this topic).

In another study, 200 patients attending dermatology departments were inspected for the presence of tinea pedis. One quarter (25%) had proven infection without knowledge (occult infection) and 59% of these had accompanying nail infection [8]. For podiatrists, is the educational message getting through? Traditionally, textbooks describe fungal foot infection as scaling of the skin, redness, blistering and itching but as we know particularly for the most common infection T rubrum, it can be very subtle with minimal redness and just a white, dry, dusty appearance accentuated in the skin creases of the soles. This is often diagnosed as dry skin and treated with emollients consequently with no effect on the infection.

One study looked at a group of tinea pedis patients to establish why some seek treatment and some do not. From their work they concluded that only where symptoms were distracting or causing inconvenience to the patient (namely itching) then they would seek treatment. Symptom free disease went untreated [9].

Untreated tinea, in time will lead to onychomycosis if untreated.

Undertreatment of tinea pedis

Once tinea has been diagnosed, a suitable treatment can be recommended or prescribed for the patient. In the UK, like many other parts of the world, dermatophytes are the most commonly isolated fungus in a UK study accounting for 89.4% of all isolates, with non-dermatophytes accounting for less than 5%. Trichophyton rubrum was the dominant species [10].

Treatment may take the form of a topical, oral or combined treatment but dermatophytes with few exceptions (see my blog here) all respond to the common over-the-counter fungal treatments but how adherent are patients to these prescribed drugs? A study published in Japan followed up 445 patients diagnosed with tinea pedis and assessed their adherence to their medication using the Morisky Medication Adherence Scale (MMAS-8) – a widely used tool to verify patients’ adherence. The study showed that there was a difference in adherence between oral and topical treatments. Namely, it was generally higher in those patients taking oral medications; however, even then adherence rates for these drugs were high in only 8.7%, moderate in 31.7% and low in 59.6% of patients. Topical drug adherence was much lower (high adherence in 8.6%, moderate in 17.4% and low in 74%) suggesting that with both types of medication there was significant low adherence. Exceptionally, one group showed more adherence – those not wishing to take oral medications [11].

Implications for podiatrists

As we know, tinea pedis is a foot infection we see all too often. In practice, I would concur with the research and say around one quarter of all new patients I see who come in with/for any foot problem, will also have tinea on their feet. One could ask, because of its high frequency, are we ignoring the infection, perhaps not looking for it or just normalising its presence? Many skin conditions we see such as eczema and psoriasis can easily co-exist with tinea pedis and so it may escape our attention. Also, do we thoroughly inspect all areas of our patients’ feet at every appointment? Tinea pedis particularly resides in the lateral toe spaces and so can easily missed or overlooked.

When we do find it, is it something we are motivated to discuss with the patient, particularly if they are consulting on a different issue and the consultation time is limited? It may seem a deflection from the more significant presenting problem of the patient. However, it is always important to bear in mind that tinea pedis usually leads to tinea cruris, tinea manuum and unsightly nail infection in the long term.

Onychomycosis is a difficult condition to treat but moreover it has a significant effect on the patient’s quality of life (see my earlier blog) and frequently suffers treatment failure (see my blog here). Moreover, in a patient with diabetes, because of the secondary cellulitis risk, tinea should not be underestimated or ignored, and the patient should be advised accordingly.

When treated is initiated, topical antifungal agents for skin infection are the most prescribed treatment but it is important to look at advice that is given out to the patient along with the tube of cream, as often the patient may not be aware of how to use it effectively. After all, we are trying to motivate the patient to use it and be successful. A lack of instructions of guidance can easily lead to treatment failure. See my earlier blog which contains a downloadable leaflet for the patient.

How much, how often and how long? These are the key points that should be conveyed to the patient. In my practice, I will sell many tubes of antifungal creams every month, but I will always make the first application on the patients’ feet to demonstrate the quantity needed and to ensure the patient knows where to apply it (everywhere below the ankle essentially). One fingertip unit (see my blog on the FTU) is enough for one application to each foot to cover this area. I also make the point that within four weeks or so they should observe a dramatic improvement in their plantar skin quality if dermatophytes are the culprit with reduction in scaling, hyperkeratosis and fissures. This is often a good motivation. I generally recommend treatment initially for 4 to 8 weeks when chronic dermatophyte infection has been diagnosed.

The final points are around avoiding recurrence and reinfection. This is a key point to get across to the patient. It has long been established that tinea pedis is a recurrent infection and virtually always comes back – probably due to an individual’s inherent susceptibility to dermatophyte infection [12]. It starts on the plantar surface and spreads from there so keeping this area fungal free is key to prevent spread to other areas. I generally recommend one week a month use of an antifungal to the feet to keep the fungal population down. Alternatively a film forming solution can be applied once and will be equally effective such as Lamisil Once® [13]. Hypochlorous solution is a useful adjunct as a spray for footwear as the product has been shown to kill dermatophytes and spores that may be in the shoes and socks (see my earlier blog on this topic).

I will always rebook a patient to return in 6-8 weeks or so to review their skin condition and continue to reinforce the key message of recurrence and maintaining the cure. If I take it seriously then the patient probably will too. Ultimately, as podiatrists we should be getting on top of the most common infection in clinic and educating our patients accordingly.

References

1. Vos T, Abajobir AA, Abate KH, Abbafati C, Abbas KM, Abd-Allah F, Abdulkader RS, Abdulle AM, Abebo TA, Abera SF, et al: Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. The Lancet 2017, 390:1211–1259.

2. Liu X, Zhang Y, Hong Y, Zhang H: Global burden of fungal skin diseases: An update from the Global Burden of Diseases Study 2019. Mycoses 2024, 67:e13770.

3. Roseeuw D: Achilles foot screening project:preliminary results of patients screened by dermatologists. J Eur Acad Dermatol Venereol 1999, 12 (supp 1):S6–S9.

4. Bristow IR, Spruce MC: Fungal foot infection, cellulitis and diabetes: a review. Diabet Med 2009, 26:548–551.

5. Maruyama R, Hiruma M, Yamauchi K, Teraguchi S, Yamaguchi H: An epidemiological and clinical study of untreated patients with tinea pedis within a company in Japan. Mycoses 2003, 46:208–212.

6. Mayser P, Hensel J, Thoma W, Podobinska M, Geiger M, Ulbricht H, Haak T: Prevalence of fungal foot infections in patients with diabetes mellitus type 1 - underestimation of moccasin-type tinea. Exp Clin Endocrinol Diabetes 2004, 112:264–268.

7. Everdell E, Shah H, Parisi R, Feustel PJ, Davis L: Non-visibility of Suspicious Lesions by Patients Leads to Later Detection of Melanoma: A Retrospective Analysis. J Am Acad Dermatol 2023.

8. Ogasawara Y: Prevalence and patients consciousness of tinea pedis and onychomycosis. Nippon Hifuka Gakkai Zasshi 2003, 44:253–260.

9. Maruyama R, Hiruma M, Yamauchi K, Teraguchi S, Yamaguchi H: An epidemiological and clinical study of untreated patients with tinea pedis within a company in Japan. Mycoses 2003, 46:208–212.

10. Phan KL, Chandler D: Clinical and mycological profile of dermatophyte infections in England. Br J Dermatol 2024, 191:i4–i5.

11. Tsunemi Y, Abe S, Kobayashi M, Kitami Y, Onozuka D, Hagihara A, Takeuchi S, Murota H, Sugaya M, Masuda K, et al: Adherence to oral and topical medication in 445 patients with tinea pedis as assessed by the Morisky Medication Adherence Scale-8. Eur J Dermatol 2015, 25:570–577.

12. Zaias N, Tosti A, Rebell G: Autosomal dominant pattern of distal sub-ungual onychomycosis caused by T Rubrum. J Am Acad Dermatol 1996, 34:302–304.

13. Ortonne JP, Korting HC, Viguie-Vallanet C, Larnier C, Savaluny E: Efficacy and safety of a new single-dose terbinafine 1% formulation in patients with tinea pedis (athlete's foot): a randomized, double-blind, placebo-controlled study. 2006, 20:1307–1313.