Athlete’s Foot(Tinea pedis)

Loh Xin Hui03/06/09

Background Athlete's foot(tinea pedis) is a fungal infection of the soles of

the feet and the interdigital spaces.

Thought to be the world’s most common dermatophytosis.experienced by up to 70% of the population at some time in their lives.

Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum are the most commonly cause tinea pedis, with T.rubrum being the most common cause worldwide.

Tinea pedis may lead to an autosensistisation reaction, called dermatophytid, which is a secondary cutaneous reaction occurs at a site distant to a primary fungal infection, resulting in tinea manuum (fungal infection of palms and finger webs), tinea unguium (fungal infection of nails), or tinea cruris (fungal infection of the groin and pubic region).

Background Tinea pedis is contagious, and spreads from

person to person through skin-to-skin contact, or indirectly through towels, clothes or floors.

The prevalence increases with age. Mostly occurs after puberty.

Adults are more likely than children to get athlete's foot. And, men get it more often than women do.

Pathophysiology Dermatophyte fungi uses enzymes, called

keratinises, to invade the superficial keratin of the skin, and the infection remains limited to this layer.

Dermatophyte cell walls also contain mannans, which can inhibit the body's immune response.

Fungi infect the superficial layer of the skin. In response to this fungal growth, the basal layer of the skin produces more skin cells than usual.

As these cells push to the surface, the skin becomes thick and scaly. Most often, the more the fungi spread, the more scales produce on the skin, causing the ring of advancing infection to form.

Risk Factors for Developing Tinea Pedis

Prolonged use of closed-in (occlusive) footwear

Prolonged exposure to moist, warm environment

Excessive sweating (hyperhidrosis) Communal bathing Contact with infected

persons/pets/materials Immuno-compromised Contact sports

Clinical Features- It takes about 2 weeks from inoculation to subsequent skin changes that are clinically visible.- There are 3 main types of athlete’s foot. Each type has a different appearance and symptoms, though any two or

even all three types may occur together.

1. Interdigital athlete’s foot - the most common kind of athlete's foot. - an infection of the web spaces between the toes,

particularly between the 4th and 5th toes. - The skin appears moist and waterlogged and is often

itchy. - The dorsal surface of the foot is usually clear, but some

extension onto the plantar surface of foot may occur.

Clinical Features2. Moccasin type athlete’s foot (hyperkeratotic

type)- involved the bottoms and sides of the feet and the heels. - has a dry scaly (flaky) appearance. The skin may be red

and the scale may range from white to silver. - is rarely itchy or uncomfortable.- may be accompanied by the presence of co-existing

fungal toenail infection. The toenails may appear thickened and discolored.

- Some people may have a co-existing fungal infection on one of their hands, so-called “two feet-one hand tinea” syndrome. Thus, it is important to examine the hands in people with athlete’s foot, and to treat them as well, if they appear red and scaly.

Clinical Features3.Inflammatory (blistering) athlete’s foot- Red, crusting rash on the soles or sides of the

feet with blisters or pustules, and discoloration on the sole of the foot.

- can be quite itchy or painful and may become secondarily infected with bacteria.

Diagnosis can be done through direct potassium hydroxide (KOH) staining for fungal elements.

A KOH preparation is performed on skin scrapings from the affected area.

KOH mixed with a blue-black dye is added to a sample from the infected tissues. This mixture makes it easier to see the dermatophytes or yeast under the microscope.

Dermatophytes or yeast seen on a KOH test indicate the person has a fungal infection.

Laboratory Studies

Treatment Medical therapy is the mainstay of treatment. Good hygiene plays an important role. It is

very important to keep feet and footwear as dry as possible.

Atheletes foot can be treated with either topical or oral antifungals or a combination of both.

Conventional treatment typically involves application of a topical medication in conjunction with hygiene measures.

Topical antifungal agents can take the form of a spray, powder, cream, or gel.

1.Topical imidazoles Work primarily by inhibiting the conversion of

lanosterol to ergosterol. The disruption in the biosynthesis of ergosterol causes significant damage to the cell wall of fungi, increasing permeability and causing cell lysis.

Excellent treatments for interdigital tinea pedis because they are effective against dermatophytes and Candida.

Treatment Options

Medication Dosage Duration

Clotrimazole 1% cream

2-3 times daily 2-4 weeks, continue for another 14 days after symptoms resolve.

Miconazole 2% cream

1-2 times daily 1month, continue for another 10 days after symptoms resolve.(Blue Book 2008, Drug Information Handbook 14th Edition)

2. Topical allylamines (terbinafine)

Inhibiting squalene epoxidases which prevents conversion of squalene to lanosterol, decreases ergosterol synthesis, causing death of fungal cells.

Effective in treating all forms of tinea pedis. Potent activity against dermatophyte fungi, so they are

useful in treating patients with refractory tinea pedis (eg, chronic hyperkeratotic).

Available as OTC product:Terbinafine 1% cream (apply to the affected area twice daily for at least 1 week.)

3. Tolnaftate (antifungal)

- Inihibits growth of dermatophytes. Exact mode of action is unknown.

- Available as OTC product: Tolnaftate 1% cream (apply to the affected area twice daily, may use up to 4 weeks)

Comparison of efficacy Several placebo controlled studies report that good foot

hygiene alone can cure athlete's foot even without medication in 30-40% of the cases. (Bedinghaus JM. et.al.2001)

There is evidence that terbinafine is better than the azoles in preventing recurrence in athelete’s foot. (Blenkinsopp A. et.al. 2004)

Another study showed that terbinafine cure slightly more infections than azoles. (Crawford F. et.al. 2007)

Tolnaftate has been found to be generally slightly less effective than azoles when used to treat tinea pedis. It is, however, useful when dealing with ringworm, especially when passed from pets to humans. (Crawford F. et.al. 2007)

Practice Points Recurrence of the infection is often due to a patient's

discontinuance of medication after symptoms abate. The recommended course of treatment is to continue to use the topical treatment for 2-4 weeks after the symptoms have subsided to ensure that the fungus has been completely eliminated.

Moccasin-type tinea pedis is often recalcitrant to topical antifungals alone, owing to the thickness of the scale on the plantar surface. The concomitant use of keratolytics(salicylic acid) with topical antifungals should improve the response to topical agents.

Severe or prolonged fungal skin infections may require treatment with oral antifungal medication.

Oral antifungal Should be considered in patients with extensive chronic

hyperkeratotic or inflammatory/vesicular tinea pedis, or for patients in whom topical treatments have failed or patients with immunocompromising conditions.

Length of therapy depends on severity of the condition.

Medication Dosage

Terbinafine 250 mg daily.

Itraconazole 100-400 mg daily.

Fluconazole 200-400 mg daily.

Ketoconazole

200-400 mg daily for 4weeks to 6 months.

Griseofulvin 500-1000 mg daily in single or divided doses.(Blue Book 2008, Drug Information 14th Edition)In a systematic review, terbinafine was found to be more effective than griseofulvin, while the efficacy of terbinafine and itraconazole were similar. (Bell-Syer SE, et al.2002)

Possible Complications Athlete’s foot is usually a mild fungal infection, but

occasionally the skin may become inflammed and sore if macerated and broken.

Once the skin is broken, bacteria can enter the epidermis through cracks in the skin, which is more vulnerable to secondary bacterial skin infection (cellulitis) - particularly common in diabetic patients, the elderly, and people with impaired function of the immune system.

The vast majority of cases are caused by Streptococcus pyogenes or Staphylococcus aureus, which should be treated with oral antibiotics.

Possible Complications In many cases, cellulitis takes less than a week to

disappear with antibiotic therapy. However, it can take months to resolve completely in more serious cases and can result in severe debility or even death if untreated.

Monotherapy with cloxacillin 500 mg QID for 7-10 days (to cover staphylococcus and streptococcus infection) is often sufficient in mild cellulitis.

In cases where streptococcus pyogenes is confirmed, oral phenoxymethylpenicillin(Pen V) 500 mg QID for 10 days is used.

For patients hypersensitivity to penicillin, oral cephalexin 500 mg QID for 7 – 10 days can be given.(Blue Book 2008, Therapeutic Guidelines: Antibiotic. 2006, Treatment of Cellulitis. UpToDate)

Patient EducationCommon practice to prevent athlete's foot infection:

Carefully drying the feet and spaces between the toes after bathing

Apply a drying powder to the feet or shoes daily to absorb moisture.

Keep socks dry and change them if they become wet.

Avoiding occlusive (non-breathable) footwear.

Wearing sandals or other open footwear when possible.

Avoid walking barefoot in locker rooms and communal showers where fungal spores may be found.

Avoid sharing socks, towels, or shoes with others.

1. Baddour LM. Treatment of Cellulitis. 2007. (UpToDate)

2. Bedinghaus JM, Niedfeldt MW. Over-the-counter Foot Remedies.

American Family Physician. 2001. Available at:

http://www.aafp.org/afp/20010901/791.html

3. Bell-Syer, SE, Hart R. et al. Oral treatments for fungal infections of the skin of the

foot. Cochrane Database Systematic Rev 2002.

4. Blenkinsopp A, Paxton P. Symptoms In The Pharmacy: A Guide To The Management

Of Common Illness. 4th Edition 2004. p.147-153.

5. Blue Book 2008.

6. Cellulitis. Available at: http://en.wikipedia.org/wiki/Cellulitis

7. Crawford F, Hollis S. Topical treatments for fungal infections of the skin and nails of

the foot. (Review). Cochrane Database of Systematic Reviews(3). July 2007.

8. Drug Information Handbook International. 14th Edition. 2006.

9. Goldstein AO, Golstein BG. Dermatophyte(tinea) Infections. Dec 2006. (UpToDate)

10. Robbins CA. Tinea Pedis: Treatment & Medication. Nov 2008. Available at:

http://emedicine.medscape.com/article/1091684-treatment

11.Stoppler M. How to Prevent Athlete’s Foot. July 2007. Available at:

http://www.medicinenet.com/script/main/art.asp?articlekey=55264

12.Therapeutic Guidelines: Antibiotic. 2006(13).