What is the differential diagnosis (diff) and treatment for athlete's foot?

Differential Diagnosis and Treatment of Athlete's Foot

Differential Diagnosis

Athlete's foot (tinea pedis) is a fungal infection primarily caused by dermatophytes, most commonly Trichophyton rubrum and Trichophyton mentagrophytes. The differential diagnosis includes:

• Tinea pedis (athlete's foot) - characterized by fine scaly or vesiculopustular eruption, often itchy, commonly affecting the spaces between toes 1
• Bacterial infection - may present as secondary infection in dermatophytosis complex with inflammation, maceration and odor 2
• Dermatitis - can mimic or coexist with tinea pedis
• Psoriasis - may affect the feet with scaling and erythema
• Contact dermatitis - reaction to shoes or other foot products

Clinical Presentation

Athlete's foot typically presents as:

• Fine scaly or vesiculopustular eruption that is often itchy 1
• Lesions commonly involve the fissures and scaling between toes 1
• May present as asymptomatic dermatophytosis simplex or symptomatic dermatophytosis complex with secondary bacterial infection 2
• In dermatophytosis complex, there may be inflammation, maceration, and odor 2

Risk Factors

Several factors increase the risk of developing athlete's foot:

• Participation in swimming and running (especially marathon running) with documented infection rates up to 22% 1
• Warm, humid environments 1
• Male gender (affects men more than women) 1
• Obesity and diabetes are additional risk factors 1
• Wearing occlusive footwear 1
• Use of communal bathing facilities 1

Treatment

For athlete's foot (tinea pedis), topical terbinafine 1% cream is the most effective first-line treatment, applied twice daily for 1 week between the toes or 2 weeks on the bottom or sides of the foot. 3

Topical Antifungal Options:

• Terbinafine 1% cream:

  • Apply twice daily (morning and night) 3
  • For infections between the toes only: use for 1 week 3
  • For infections on the bottom or sides of the foot: use for 2 weeks 3
  • Highly effective regardless of formulation type, treatment duration, or application frequency 4

• Ciclopirox olamine cream or gel (0.77%):

  • Apply twice daily to affected areas for 4 weeks 1
  • Particularly effective for dermatophytosis complex due to its antifungal, antibacterial, and anti-inflammatory properties 2
  • Shown to be superior to vehicle with 60% treatment success versus 6% for vehicle 5

Oral Antifungal Options (for severe or resistant cases):

• Terbinafine:

  • Highly effective oral antifungal with fungicidal activity against dermatophytes 6
  • Well tolerated with relatively low potential for drug interactions 6

• Itraconazole:

  • 100 mg orally once daily for 15 days has shown 87% mycological cure rate 1

• Fluconazole:

  • Has been used prophylactically in athletes but should only be used in consultation with an infectious disease expert 1

Prevention Measures

To prevent recurrence of athlete's foot:

• Wear well-fitting, ventilated shoes 3
• Change shoes and socks at least once daily 3
• Use foot powder after bathing (associated with decline in tinea pedis rates from 8.5% to 2.1%) 1
• Carefully and thoroughly dry between toes after showering 1
• Daily changes of socks and periodic cleaning of athletic footwear 1
• Avoid walking barefoot in communal areas such as swimming pools and locker rooms 1

Special Populations

Athletes:

• Higher prevalence due to trauma, increased sweating, and exposure to infectious dermatophytes 1
• Swimmers have shown a threefold increase in occurrence (23%) compared to general population (8%) 1
• Consider prophylactic measures during competitive seasons 1

Diabetic Patients:

• Diabetics are at higher risk of complications from fungal foot infections 1
• Careful monitoring and aggressive treatment is recommended to prevent secondary bacterial infections 1
• Diseased nails with sharp edges can injure surrounding tissue and serve as entry points for bacteria 1

Common Pitfalls and Caveats

• Failure to differentiate between simple tinea pedis and dermatophytosis complex with bacterial involvement 2
• Inadequate duration of treatment leading to recurrence 1
• Not addressing predisposing factors such as occlusive footwear or excessive moisture 3
• Overlooking the possibility of concomitant onychomycosis, which may serve as a reservoir for reinfection 1
• Treating clinically uninfected wounds with antibiotics (not recommended) 1