What is the most updated protocol for diagnosis and management of Tinea circinata (ringworm) in a patient with a history of resistance to multiple lines of antifungal treatment?

Management of Treatment-Resistant Tinea Corporis (Tinea Circinata)

Diagnostic Confirmation in Resistant Cases

In cases of tinea corporis resistant to multiple antifungal lines, you must obtain mycological confirmation with culture and consider antifungal susceptibility testing before proceeding with further treatment. 1

• Collect specimens via scalpel scraping from the active border of lesions for both microscopy (potassium hydroxide preparation) and culture on Sabouraud agar 1
• Antifungal susceptibility testing (AST) is specifically recommended for superficial isolates in patients who have failed to respond to antifungal agents or have relapsing infection 1
• Culture plates should be incubated for at least 2 weeks to allow adequate growth of dermatophytes 1
• Dermoscopy can be used as an adjunctive diagnostic tool to visualize fungal elements more clearly 1
• Rule out immunosuppression, diabetes, or other predisposing factors that may contribute to treatment failure 2

First-Line Systemic Therapy for Resistant Cases

Oral terbinafine 250 mg daily for 2-4 weeks is the preferred first-line agent for treatment-resistant tinea corporis caused by Trichophyton species. 1, 3

• Terbinafine demonstrates superior efficacy against Trichophyton species (the most common cause of tinea corporis) compared to other agents 1
• Alternative dosing: 250 mg daily for 1-2 weeks has shown effectiveness in clinical trials 3
• Topical therapy alone is not recommended and should not be used as monotherapy in resistant cases 1

Second-Line Systemic Options

If terbinafine fails or is contraindicated, itraconazole 100-200 mg daily for 2-4 weeks is the recommended second-line agent. 1, 3

• Itraconazole has activity against both Trichophyton and Microsporum species 1
• Pulse dosing regimen: 200 mg daily for 7 days is an effective alternative that may improve compliance 3
• Fluconazole 50-100 mg daily for 2-3 weeks or 150 mg once weekly for 2-3 weeks can be used as an alternative 3

Management Algorithm for True Resistance

When clinical improvement is absent after appropriate first-line therapy:

1. Reassess compliance and drug absorption - ensure the patient is taking medication as prescribed and with fatty food if using griseofulvin 1
2. Verify the diagnosis - repeat mycological examination to confirm dermatophyte infection and rule out other conditions 1
3. Perform antifungal susceptibility testing using reference methods (EUCAST or CLSI) to identify resistant strains 1
4. Check for reinfection sources - examine household contacts, pets, and fomites that may be causing reinfection 4
5. Consider immunosuppression - evaluate for HIV, diabetes, or other immunocompromising conditions 4, 2

Third-Line and Alternative Therapies

For cases with documented antifungal resistance or failure of conventional therapy, consider voriconazole or posaconazole. 1, 2

• These agents should be reserved for truly refractory cases with documented resistance 1
• Therapeutic drug monitoring is recommended for voriconazole and posaconazole to ensure adequate drug levels and avoid toxicity 1
• Natural herbal treatments, laser therapy, and photodynamic therapy can be considered in patients who cannot tolerate systemic antifungals, though evidence is limited 2

Duration and Monitoring

Treatment should continue for at least 1 week after complete clinical clearing of the infection. 5

• Repeat mycological sampling is recommended until mycological clearance is achieved, not just clinical resolution 1
• For extensive or resistant infections, treatment duration may need to be extended beyond standard protocols 1
• Monitor for drug interactions, particularly with itraconazole and voriconazole, which interact with CYP3A4 substrates 1

Critical Pitfalls to Avoid

• Do not continue the same failing regimen - if there is no clinical improvement after an appropriate treatment course, switch agents rather than extending duration 1
• Do not use topical therapy alone in resistant cases, as it will not achieve adequate penetration 1
• Do not ignore the possibility of non-dermatophyte infection - other conditions may mimic tinea corporis 1
• Do not overlook drug interactions - azoles have significant interactions with many medications including warfarin, antihistamines, and immunosuppressants 1
• Antifungal resistance is emerging among dermatophytes, making antifungal stewardship and appropriate use of susceptibility testing increasingly important 4, 2

Adjunctive Measures

• Topical antifungal shampoos or creams (ketoconazole 2%, selenium sulfide) can be used to reduce spore transmission but not as sole therapy 1
• Address environmental factors including moisture, occlusive clothing, and hygiene practices 5
• Screen and treat household contacts and pets if applicable 1