What is Tinea pedis?
- It is commonly termed as athlete’s foot.
- The term tinea pedis refers to contagious dermatophyte infections of the feet.
- These infections often involve the interdigital spaces, but chronic diffuse peeling can affect the entire sole.
- It is mostly seen in individuals whose feet are sweaty because of tightfitting shoes.
- Geographical distribution:
- It is distributed worldwide and is most commonly found in hot, tropical, urban regions.
Epidemiology of Tinea pedis:
- Etiology:
- The commonest causes of tinea pedis in Europe and North America are the anthropophilic dermatophytes Trichophyton rubrum, T. mentagrophytes var. interdigitale and Epidermophyton floccosum.
- T. rubrum is the principal cause of chronic tinea pedis.
- Tinea pedis being a contagious condition it is easily transmitted from person to person.
- Transfer within house- holds has been reported, but the main spread occurs in communal bathing places and showers.
- The infection is usually taken by walking barefoot on contaminated floors.
- Tinea pedis is a modern disease, linked with the wearing of occlusive footwear.
- The growth of the fungus requires heat and moisture and the frequency of infections in temperate climates increases during the summer months.
- Tinea pedis is more frequently seen in men than women.
- It often initiates in late childhood or adolescence and is most frequent between the ages of 20 and 50.
- The disease is most prevalent among individuals of places where bathing facilities are shared such as swimming pools and fitness centres, involved in sporting activities, or living in closed communities, such as residential schools and prisons.
- Tinea pedis has been found to affect about 15-20% of adult males.
- The prevalence of infection is much higher among industrial workers such as coal miners, who are exposed on a daily basis to infection.
- It has been estimated that about one-third of patients with tinea pedis also have a fungal nail infection.
Clinical manifestations of tinea pedis:
- Bilateral involvement of tinea pedis is more common but may be unilateral too.
- Three main clinical forms may be distinguished:
- 1) acute or chronic interdigital infection
- 2) chronic hyperkeratotic (moccasin or dry type) infection of the soles and lateral borders of the feet
- 3) vesicular (inflammatory) infection of the instep and sole.
- 4) Occasional patients develop an acute ulcerative infection of the soles.
- It is usual for patients to develop a combined clinical presentation involving two or even three of these forms of tinea pedis.
- Acute or chronic interdigital infection:
- It is the commonest form of tinea pedis characterized by itching, peeling, maceration and fissuring of the toe webs.
- The skin beneath the whitish build-up of debris may appear red and weeping.
- A foul odour is sometimes present.
- The cleft between the fourth and fifth toes is most often involved, but the infection may spread to adjacent areas of the feet, including the toenails.
- In a patient with supposed chronic tinea pedis, an absence of nail involvement makes the diagnosis of dermatophytosis questionable.
2. Chronic hyperkeratotic infection:
- It is characterized by areas of pink skin covered with fine white scaling.
- Vesicles and pustules are absent.
- Hyperkeratosis is usually limited to the heels, soles and lateral borders of the feet.
- The infection may seem patchy in distribution or involve the entire weight-bearing surface, in which case the disease is termed ‘moccasin’or ‘dry type’ tinea pedis.
- The condition is usually bilateral and may be asymptomatic.
3. Vesicular infection:
- Vesicular or vesiculobullous tinea pedis is characterized by the development of vesicles, usually beginning on the sole, the instep and the interdigital clefts.
- The eruptions vary in size, may be isolated or coalesce into vesicles or bullae, and are initially filled with a clear fluid.
- After rupturing, the lesions dry, leaving a ragged ring-like border.
- The disease may resolve without treatment, but often recurs.
4. Ulcerative infection:
- It is characterized by maceration and ulceration of large areas of the soles.
- White hyper- keratosis and strong odour are common.
- Bacterial superinfection, usually with gram-negative organisms, is frequent and should be taken into account in treating this condition.
- In certain parts of the world, concomitant mould, Candida and/or bacterial infection is relatively common in patients with tinea pedis.
- These conditions usually represent secondary infection following fissuring or maceration of a toe cleft.
- The secondary infection may induce inflammation and further maceration.
Differential diagnosis of tinea pedis:
- The symptoms and clinical signs of tinea pedis can be difficult to distinguish from those of a number of other infectious causes of toe web intertrigo such as bacterial or Candida infection.
- Non-infectious conditions that resemble tinea pedis include contact dermatitis, eczema and psoriasis.
- Candidosis most often presents as mild interdigital erosion and maceration.
- It sometimes occurs in patients with diabetes mellitus and is more common in hot climates.
- It often occurs in conjunction with a dermatophyte infection.
- Other moulds which produce lesions indistinguishable from tinea pedis include Scytalidium dimidiatum (Hendersonulatoruloidea) and S. hyalinum.
- Dermatophytosis of the feet is often associated with itching.
- In contrast, gram-negative bacterial infection tends to produce more painful inflammatory lesions, often with marked erosion of the skin.
- The clinical appearance of erythrasma (Corynebacterium minutissimum infection) is difficult to distinguish from interdigital tinea pedis.
- Laboratory tests should be performed in any patient with foot lesions of undetermined origin.
Lab diagnosis of tinea pedis:
- Microscopy:
- Direct microscopic examination of infected material should confirm a clinical diagnosis of dermatophyte infection.
- It is sometimes possible to distinguish a yeast infection from tinea pedis.
- Culture:
- Isolation of the aetiological agent in culture will permit the species of fungus involved to be determined.
- Media containing cycloheximide (actidione)should not be used if infection with a Scytalidium species is suspected.
- Wood’s light examination of the lesion should be performed to establish whether the patient has erythrasma.
- The coral red fluorescence characteristic of this condition does not, however, exclude coexistent tinea pedis.
Treatment of tinea pedis:
- Interdigital tinea pedis will often respond to topical treatment with an imidazole compound, such as bifonazole, clotrimazole, econazole, isoconazole, miconazole, oxiconazole, sulconazole, terconazole or tioconazole, or an allylamine, such as naftifine or terbinafine.
- Terbinafine, applied to the toe clefts and other affected sites
– morning and evening for upto 2 weeks. - Imidazoles, used for up to 4 weeks.
- To help prevent the infection from spreading, it is beneficial to apply cream to the soles.
- The recurrence rate is quite high, and chronic infection with minor scaling may persist.
- Exacerbations of previous infection may also occur.
- The common infections are mixed fungal and bacterial infections of the feet.
- Thus, topical antifungal preparations that are effective against dermatophytosis and candidosis, and those possessing some antibacterial action (such as miconazole) are often advised.
- Oral treatment with terbinafine (250mg/day for 2-6 weeks) or itraconazole (100mg/day for 4 weeks) should be given in addition to topical treatment (which should be continued for 8 weeks or longer) if the disease is extensive, involving the sole and dorsum of the foot, or if there is acute inflammation.
- However, relapse is common.
- Chronic tinea pedis is often linked with infection of the nails.
- Insufficient treatment of onychomycosis may result in reinfection of the feet.
- Tinea pedis is a chronic condition which seldom resolves if left untreated.
- Exacerbations, that occurs in the summer, alternate with partial remissions.
- Nevertheless, the prognosis in general remains benign.
Prevention of tinea pedis:
- It is essential to inform the patient of measures that can help to control the infection or prevent reinfection.
- These consist of
– antibacterial soaps
– daily bathing of the feet
– followed by thorough drying of the toes and inter- digital spaces
– liberal application of antifungal powders to the feet after bathing
– wearing of cotton socks to absorb sweat
– frequent changing of socks
– application of antifungal powders to footwear
– avoidance of occlusive footwear that increases sweating
– wearing of protective footwear in hotels, changing rooms, gymnasiums and other public facilities. - Educating infected individuals not to expose others to their infection by not walking barefoot on the floors of communal changing rooms and by avoiding public baths and showers can help to reduce the spread of tinea pedis.
- Some helpful preventive measures are frequent hosing of the floors of public baths and the discouraging of antifungal foot dips near communal baths.