What if your ringworm won’t clear? A clear guide to terbinafine‑resistant fungal infections and what to do next.

Case Review: 

28‑year‑old female presents with 3 months of an expanding, scaly rash on bilateral ankles; treated twice with topical terbinafine without improvement. PMH: none; vitals: afebrile, HR 78; exam: annular erythematous plaques with central clearing and scale; no nail involvement. Current meds: oral contraceptive. Pertinent negative: no recent travel or immunosuppression.

Description: 

The patient likely has dermatophytosis caused by a Trichophyton species with an SQLE gene mutation that reduces terbinafine binding; this allows fungal growth to continue despite topical therapy, producing the persistent scaly plaques and spread over weeks. Test your understanding of this mechanism with practicetest.

Clinical Insight: 

Recognize persistent or spreading tinea that fails standard therapy as a red flag for resistance; send for fungal identification and consider systemic antifungal therapy or longer courses when resistance is suspected. Review the quick summary for exam‑style recall with studysheet.

Why this matters:

Resistant dermatophyte infections are increasing globally and can cause prolonged symptoms, transmission, and treatment delays if not identified.

Quick take-away: 

1. Confirm diagnosis with skin scraping or culture.

2. If treatment fails, request susceptibility or molecular testing where available.

3. Use alternative oral antifungals and longer durations guided by results.

4. Counsel on hygiene and avoid steroid‑antifungal combinations.

Common pitfalls to watch for: 

• Assuming any scaly rash is tinea without testing.

• Continuing short topical courses when infection is extensive.

• Using topical steroids that mask or worsen fungal infections.

Test your knowledge with our free flashcards on terbinafine resistance and dermatophyte infections