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Tinea Pedis

- Precautions (griseofulvin): - Should be used only in severe cases - Periodic monitoring of organ-system functioning, including renal, hepatic, and hematopoietic - Possible photosensitivity reactions - Lupus erythematosus, lupus-like syndromes, or exacerbation of existing lupus erythematosus has been reported.

- Significant possible interactions (griseofulvin): - Decreases activity of warfarin-type anticoagulants - Barbiturates usually depress griseofulvin activity. - May potentiate effect of alcohol, producing tachycardia and flush

para>Rare in younger children; common in teens

Geriatric Considerations

Elderly are more susceptible to outbreaks because of immunocompromise and impaired perfusion of distal extremities.

ETIOLOGY AND PATHOPHYSIOLOGY

Superficial infection caused by dermatophytes that thrive only in nonviable keratinized tissue.

  • Trichophyton mentagrophytes (acute)
  • Trichophyton rubrum (chronic)
  • Trichophyton tonsurans
  • Epidermophyton floccosum

Genetics

No known genetic pattern.

RISK FACTORS

  • Hot, humid weather
  • Sweating
  • Occlusive/tight-fitting footwear
  • Immunosuppression
  • Prolonged application of topical steroids

GENERAL PREVENTION

  • Good personal hygiene
  • Wearing rubber or wooden sandals in community showers, bathing places, locker rooms
  • Careful drying between toes after showering or bathing; blow-drying feet with hair dryer may be more effective than drying with towel.
  • Changing socks and shoes frequently
  • Applying drying or dusting powder
  • Applying topical antiperspirants
  • Putting on socks before underwear to prevent infection from spreading to groin

COMMONLY ASSOCIATED CONDITIONS

  • Hyperhidrosis
  • Onychomycosis
  • Tinea manuum/unguium/cruris/corporis

DIAGNOSIS

HISTORY

  • Itchy, scaly rash on foot, usually between toes; may progress to fissuring/maceration in toe web spaces.
  • May be associated with onychomycosis and other tinea infections

PHYSICAL EXAM

  • Acute form: self-limited, intermittent, recurrent; scaling, thickening, and fissuring of sole and heel; scaling or fissuring of toe webs; or pruritic vesicular/bullous lesions between toes or on soles
  • Chronic form: most common; slowly progressive, pruritic erythematous erosion/scales between toes, in digital interspaces; extension onto soles, sides/dorsum of feet (moccasin distribution); if untreated, may persist indefinitely
  • Other features: strong odor, hyperkeratosis, maceration, ulceration
  • Tinea pedis may occur unilateral or bilateral.
  • Seconday eruptions called dermatophytid reactions may occur at distant sites.

DIFFERENTIAL DIAGNOSIS

  • Interdigital type: erythrasma, impetigo, pitted keratolysis, candidal intertrigo
  • Moccasin type: psoriasis vulgaris, eczematous dermatitis, pitted keratolysis
  • Inflammatory/bullous type: impetigo, allergic contact dermatitis, dyshidrotic eczema (negative KOH examination of scrapings), bullous disease

DIAGNOSTIC TESTS & INTERPRETATION

Wood lamp exam will not fluoresce unless complicated by another fungus, which is uncommon: Malassezia furfur (yellow to white), Corynebacterium (red), or Microsporum (blue-green).

Initial Tests (lab, imaging)

Testing is not needed in typical presentation.

  • Direct microscopic exam (potassium hydroxide) of scrapings of the lesions
  • Culture (Sabouraud medium)

Test Interpretation

  • Potassium hydroxide preparation: septate and branched mycelia
  • Culture: dermatophyte

TREATMENT

Treatment is generally with topical antifungal medications for up to 4 weeks and is more effective than placebo:

  • Acute treatmentAluminum acetate soak (Burow solution; Domeboro, one pack to one quart warm water) to decrease itching and acute eczematous reactionAntifungal cream of choice BID after soaks
  • Chronic treatment:Antifungal creams BID, continuing for 3 days after the rash is resolved: terbinafine 1% (possibly most effective topical), clotrimazole 1%, econazole 1%, ketoconazole 2%, tolnaftate 1%, etc. (2)[A]May try systemic antifungal therapy; see below (consider if concomitant onychomycosis or after failed topical treatment)

GENERAL MEASURES

  • Soak with aluminum chloride 30% or aluminum subacetate for 20 minutes BID.
  • Careful removal of dead/thickened skin after soaking or bathing
  • Treatment of shoes with antifungal powders
  • Avoidance of occlusive footwear
  • Chronic or extensive disease or nail involvement requires oral antifungal medication and systemic therapy.

MEDICATION

For use when topical therapy has failed

First Line

  • Systemic antifungals (3)[A]:Itraconazole (Sporanox): 200 mg PO BID for 7 days (cure rate >90%)Terbinafine (Lamisil): 250 mg/day PO for 14 days
  • If concomitant onychomycosis:Itraconazole: 200 mg PO BID for first week of month for 3 months. Liver function testing is recommended.Terbinafine: 250 mg/day PO for 12 weeks, or pulse dosing: 500 mg/day PO for 1st week of month for 3 months. Not recommended if creatinine clearance <50 mL/min.
  • Pediatric dosing options:Griseofulvin: 10 to 15 mg/kg/day or dividedTerbinafine:10 to 20 kg: 62.5 mg/day20 to 40 kg: 125 mg/day>40 kg: 250 mg/day
  • Itraconazole: 5 mg/kg/day
  • Fluconazole: 6 mg/kg/week
  • Contraindications: itraconazole, pregnancy Category C
  • Precautions: All systemic antifungal drugs may have potential hepatotoxicity.
  • Significant possible interactions: Itraconazole requires gastric acid for absorption; effectiveness is reduced with antacids, H2 blockers, proton pump inhibitors, etc. Take with acidic beverage such as soda if on antacids.

Second Line

  • Systemic antifungals: griseofulvin 250 to 500 mg of microsize BID daily for 21 days
  • Contraindications (griseofulvin):Patients with porphyria, hepatocellular failurePatients with history of hypersensitivity to griseofulvin
  • Precautions (griseofulvin):Should be used only in severe casesPeriodic monitoring of organ-system functioning, including renal, hepatic, and hematopoieticPossible photosensitivity reactionsLupus erythematosus, lupus-like syndromes, or exacerbation of existing lupus erythematosus has been reported.
  • Significant possible interactions (griseofulvin):Decreases activity of warfarin-type anticoagulantsBarbiturates usually depress griseofulvin activity.May potentiate effect of alcohol, producing tachycardia and flush

ISSUES FOR REFERRAL

If extensive or resistant disease, especially in immunocompromised host

ADDITIONAL THERAPIES

  • Treatment of secondary bacterial infections
  • Treatment of eczematoid changes

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Avoid sweating feet.

Patient Monitoring

Evaluate for response, recognizing that infections may be chronic/recurrent.

DIET

No restrictions

PATIENT EDUCATION

See "General Prevention. "

PROGNOSIS

  • Control but not complete cure
  • Infections tend to be chronic with exacerbations (e.g., in hot weather).
  • Personal hygiene and preventive measures such as open-toed sandals, careful drying, and frequent sock changes are essential.

COMPLICATIONS

  • Secondary bacterial infections (common portal of entry for streptococcal infections, producing lymphangitis/cellulitis of lower extremity)
  • Eczematoid changes

REFERENCES

11 Ameen M. Epidemiology of superficial fungal infections. Clin Dermatol. 2010;28(2):197 " 201.22 Crawford F, Hollis S Topical treatments for fungal infections of the skin and nails of the foot. Cochrane Database Syst Rev. 2007;(3):CD001434.33 Bell-Syer SE, Khan SM, Torgerson DJ. Oral treatments for fungal infections of the skin of the foot. Cochrane Database Syst Rev. 2012;(10):CD003584.

ADDITIONAL READING

  • Gupta AK, Cooper EA. Update in antifungal therapy of dermatophytosis. Mycopathologia. 2008;166(5 " 6):353 " 367.
  • Rotta I, Sanchez A, Gon §alves PR, et al. Efficacy and safety of topical antifungals in the treatment of dermatomycosis: a systematic review. Br J Dermatol. 2012;166(5):927 " 933.

SEE ALSO

Dermatitis, Contact; Dyshidrosis

CODES

ICD10

B35.3 Tinea pedis

ICD9

110.4 Dermatophytosis of foot

SNOMED

  • 6020002 Tinea pedis (disorder)
  • 25956006 Tinea pedis due to Trichophyton (disorder)
  • 43581009 Tinea pedis due to Epidermophyton (disorder)

CLINICAL PEARLS

  • Treatment is generally with topical antifungal medications for up to 4 weeks.
  • Tinea pedis is often recurrent/chronic in nature.
  • Careful drying between toes after showering or bathing helps prevent recurrences. (Blow drying feet with hair dryer may be more effective than drying with towel.)
  • Socks should be changed frequently. Put on socks before underwear to prevent infection from spreading to groin (tinea cruris).
  • Dusting and drying powders (containing antifungal agents) may prevent recurrences.