What is Tinea corporis and how is it treated?

Tinea Corporis: Diagnosis and Treatment

Tinea corporis (ringworm) is a common superficial fungal infection that presents as well-demarcated, circular or oval, scaly patches or plaques with raised borders, and should be treated with topical antifungal medications as first-line therapy for localized infections, with oral antifungals reserved for extensive or resistant cases. 1

Clinical Presentation and Diagnosis

Tinea corporis typically presents with the following characteristics:

• Well-demarcated, sharply circumscribed, oval or circular lesions
• Mildly erythematous, scaly patches or plaques with raised leading edges
• Often accompanied by mild pruritus 2

Diagnosis should be confirmed through:

• Microscopic examination using potassium hydroxide (KOH) preparation
• Fungal culture (gold standard) for cases that are:
  • Widespread
  • Severe
  • Resistant to treatment
  • Diagnostically uncertain 1, 2

Dermoscopy can be a useful non-invasive diagnostic tool to differentiate tinea corporis from other annular lesions like pityriasis rosea, which is important as their treatments differ significantly 1.

Treatment Algorithm

1. Localized Infections (First-Line)

Topical antifungal agents:

• Terbinafine 1% cream: Apply once daily for 1-2 weeks (84.2% mycological cure rate) 1, 3
• Clotrimazole 1% cream: Apply twice daily for 2 weeks 1, 4
• Miconazole 2% cream: Apply twice daily for 2 weeks 1
• Naftifine 1% cream: Apply once daily (shown to be 2.38 times more effective than placebo) 1, 4

2. Extensive, Resistant, or Severe Infections

Oral antifungal medications:

• Terbinafine: 250mg daily for 1-2 weeks (especially effective for Trichophyton species) 1
• Itraconazole: 100mg daily for 15 days (87% mycological cure rate compared to 57% with griseofulvin) 5, 1
• Griseofulvin: 15-20mg/kg/day for 6-8 weeks (particularly for Microsporum species) 1
• Fluconazole: 150mg once weekly for 2-4 weeks (alternative option) 6

Treatment Duration and Follow-up

• Continue treatment for at least one week after clinical resolution 1, 7
• Clinical improvement typically occurs within 1-2 weeks 1
• The endpoint of treatment should be mycological cure, not just clinical improvement 1
• Follow-up mycological examination is recommended for resistant or recurrent cases 1

Prevention and Control Measures

• Examine and treat all household members for anthropophilic infections 1
• Clean personal items with disinfectant and avoid sharing towels and other fomites 5, 1
• Apply antifungal powders containing miconazole or clotrimazole to prevent reinfection 1
• For athletes, consider prophylactic treatment before competitive seasons (though this should be done in consultation with infectious disease experts) 5

Important Considerations and Caveats

• Misdiagnosis risk: Tinea corporis can mimic many other annular lesions, leading to inappropriate treatment 2
• Steroid caution: Combination antifungal/steroid agents should be used with caution due to potential for causing atrophy and other steroid-associated complications 7
• Prior medication interference: Diagnosis can be difficult with prior use of medications such as calcineurin inhibitors or corticosteroids 2
• Treatment failure: If standard treatment fails, consider:
  • Non-compliance
  • Reinfection from untreated contacts
  • Misdiagnosis
  • Need for systemic therapy 1, 2

The evidence strongly supports that both topical and oral antifungal treatments are effective for tinea corporis, with the choice depending on the extent and severity of infection. Newer medications like terbinafine and naftifine have demonstrated high efficacy with shorter treatment durations and fewer applications needed compared to older agents 1, 4.