What is the recommended first‑line therapy and management for tinea corporis, including duration, topical versus oral options, and special considerations for extensive disease, immunocompromised patients, pregnant or lactating patients, and children under two years old?

Treatment of Tinea Corporis

For localized tinea corporis, use topical terbinafine 1% cream once daily for 1-2 weeks as first-line therapy; for extensive disease, treatment failure, or immunocompromised patients, use oral terbinafine 250 mg daily for 1-2 weeks. 1

First-Line Topical Therapy for Localized Disease

• Allylamine agents (terbinafine or naftifine) applied once daily for 1-2 weeks are preferred over azoles due to shorter treatment duration and superior efficacy 1
• Alternative topical options include clotrimazole cream or miconazole cream applied twice daily for 2-4 weeks for mild to moderate disease 2
• Topical therapy alone is appropriate for localized, limited skin involvement in immunocompetent patients without prior treatment failure 1
• Treatment should continue for at least one week after clinical clearing of infection 3

Oral Antifungal Therapy Indications

Oral therapy is indicated when:

• The infection is extensive or covers a large body surface area 1, 4
• The infection is resistant to topical treatment 2, 1
• The patient is immunocompromised 1, 5
• Hair follicle involvement is present 5
• Multiple lesions are present or the infection is deep, recurrent, or chronic 4

Oral Antifungal Agent Selection

Terbinafine is the first-line oral agent:

• Terbinafine 250 mg daily for 1-2 weeks achieves an 87.1% mycological cure rate at 6 weeks follow-up 1
• Terbinafine is particularly effective against Trichophyton tonsurans infections 6, 2
• Baseline liver function tests are recommended before initiating terbinafine, especially with pre-existing hepatic abnormalities 2

Itraconazole is an alternative oral agent:

• Itraconazole 100 mg daily for 15 days achieves an 87% mycological cure rate, superior to griseofulvin's 57% cure rate 6, 1
• Itraconazole has important drug interactions with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin 2
• Itraconazole is licensed for children over 12 years in the UK, though used off-label in younger children in some countries 2

Fluconazole can be considered as a third-line option:

• Fluconazole 50-100 mg daily or 150 mg once weekly for 2-3 weeks is effective 7
• However, fluconazole is not licensed for tinea in children under 10 years in the UK and is less cost-effective than terbinafine with limited comparative efficacy data 2

Special Population Considerations

Children under 2 years:

• Topical antifungals remain first-line for localized disease 1
• Oral terbinafine dosing should be weight-based when systemic therapy is required 5

Immunocompromised patients:

• Oral antifungal therapy is indicated even for limited disease 1, 5
• Extended treatment duration may be necessary 4

Pregnant and lactating patients:

• Topical therapy is preferred when possible to minimize systemic exposure 1
• Oral antifungals should be avoided during pregnancy unless absolutely necessary, as safety data are limited

Diagnostic Confirmation

• Confirm diagnosis before treatment by performing potassium hydroxide (KOH) preparation or fungal culture to identify the causative organism 1
• Specimens should be collected using scalpel scraping from the active border of the lesion 2
• Dermoscopy is a useful non-invasive diagnostic tool when clinical diagnosis is uncertain 4

Treatment Monitoring and Endpoints

• Mycological cure, not just clinical response, is the definitive treatment endpoint 2, 1
• Follow-up with repeat mycology sampling until clearance is documented is necessary 2, 1
• In cases of clinical improvement but ongoing positive mycology, continue current therapy for a further 2-4 weeks 8

Prevention of Recurrence

Essential preventive measures include:

• Screen and treat all family members, as over 50% of household contacts may be affected with anthropophilic species like T. tonsurans 2, 1
• Clean all fomites (combs, brushes, towels) with disinfectant or 2% sodium hypochlorite solution 2, 1
• Avoid skin-to-skin contact with infected individuals and cover active lesions 6, 2
• Do not share towels and other personal items 6, 2

Common Pitfalls to Avoid

• Do not use griseofulvin as first-line therapy due to longer treatment duration and lower efficacy compared to terbinafine 2, 1
• Avoid combination antifungal-corticosteroid agents as routine therapy, as they should be used with caution due to potential for causing atrophy and other steroid-associated complications 3, 5
• Treatment failure may result from poor compliance, suboptimal absorption, or relative insensitivity of the organism 8
• Do not rely solely on clinical appearance for diagnosis, as many conditions can mimic tinea corporis (eczema, psoriasis) 4, 5
• Higher doses of terbinafine (500 mg daily) do not provide additional benefit over standard 250 mg dosing 9