A 32-year-old woman presents with a 6-week history of pruritic, scaly patches on the groin and inner thighs with a well-demarcated erythematous border. KOH mount from the lesion shows branching septate hyphae. She has tried topical antifungal creams for 3 weeks without improvement. What is the most appropriate next step in management?

Explanation

## Clinical Assessment This patient has **tinea cruris** (confirmed by KOH mount showing branching septate hyphae) that has failed to respond to 3 weeks of topical therapy. The well-demarcated border and chronic nature (6 weeks) indicate dermatophyte infection rather than candidiasis or other causes. ## Management Strategy for Treatment-Resistant Tinea **Key Point:** Topical antifungals are first-line for localized tinea, but failure after 2–3 weeks of adequate therapy warrants escalation to systemic antifungals. **High-Yield:** Oral terbinafine is the preferred systemic agent for dermatophyte infections because it: - Achieves high concentrations in skin, hair, and nails - Has superior efficacy against *Trichophyton* and *Epidermophyton* species - Requires shorter duration (2–4 weeks for tinea corporis/cruris) compared to azoles - Has better compliance and fewer drug interactions than itraconazole ## Rationale for Fungal Culture Fungal culture should be performed **before** starting systemic therapy to: 1. Confirm dermatophyte species (guides choice of antifungal) 2. Detect resistance patterns (rare but important if azole-resistant strains are suspected) 3. Rule out non-dermatophyte causes (e.g., *Candida*, *Malassezia*) that may require different management ## Recommended Dosing | Agent | Dose | Duration | Notes | |-------|------|----------|-------| | Terbinafine | 250 mg daily | 2–4 weeks | First-line for dermatophyte; faster cure | | Itraconazole | 200 mg daily | 2–4 weeks | Alternative if terbinafine contraindicated | | Fluconazole | 150 mg weekly | 2–4 weeks | Less effective; reserve for candidiasis | **Clinical Pearl:** Tinea cruris in women is less common than in men (due to lower moisture in the groin area), so ensure proper diagnosis and consider checking for other sites (feet, nails) that may harbour the same organism. ## Why Not Other Options? - **Continuing topical therapy alone:** Failure after 3 weeks indicates inadequate penetration or resistance; escalation is needed. - **Referral for malignancy:** The clinical presentation is classic for dermatophytosis; malignancy is not a differential at this stage. - **Systemic corticosteroids:** These suppress local immunity and worsen fungal infections; contraindicated in active tinea.