Beclomethasone (Topical Corticosteroid)
The patient most likely applied a topical corticosteroid ointment, specifically beclomethasone, which temporarily suppressed symptoms but allowed the underlying fungal infection to persist and worsen once discontinued. 1
Clinical Reasoning
The clinical presentation describes classic tinea corporis (ringworm) with:
- Itchy, scaly lesions with central clearing and raised margins
- Microscopic confirmation of fungal mycelium
- Temporary symptom relief with an ointment
- Recurrence and worsening after stopping the ointment 1
This pattern is pathognomonic for inappropriate corticosteroid use on a fungal infection, creating what is known as "tinea incognito." 1
Why Corticosteroids Provide False Relief
Topical corticosteroids like beclomethasone suppress the inflammatory response, which:
- Temporarily reduces itching and visible inflammation
- Creates the illusion of improvement
- Allows the fungal infection to proliferate unchecked beneath the surface
- Results in more extensive disease when discontinued 1
Why Not the Other Options
Terbinafine (Option A): This allylamine antifungal is highly effective against dermatophytes with fungicidal activity. 2, 3 If she had used terbinafine, the infection would have been cured, not recurred. Terbinafine achieves mycological cure in >80% of dermatophyte infections. 3
Miconazole (Option C): This topical azole antifungal is effective for treating tinea corporis and would have resulted in cure, not recurrence. 1, 4 Topical azoles including miconazole are recommended first-line treatments for superficial dermatophyte infections. 1
Neomycin (Option D): This is an antibacterial agent with no antifungal activity. It would provide no symptom relief for a fungal infection and would not explain the clinical course described. 1
Common Clinical Pitfall
This case illustrates a critical diagnostic error: applying corticosteroids to undiagnosed skin lesions without confirming the absence of fungal infection. 1 The temporary improvement misleads both patient and provider, while the underlying mycosis spreads. 1
Correct Management Approach
For confirmed tinea corporis with fungal mycelium on microscopy:
- Topical antifungals are first-line: azoles (clotrimazole, miconazole) or allylamines (terbinafine) applied for 2-4 weeks 1, 5
- Avoid all corticosteroids on active fungal infections 1
- Terbinafine 1% cream achieves clinical cure rates >80% when applied once or twice daily 3, 5
- Mycological cure rates favor terbinafine over placebo (RR 4.51,95% CI 3.10 to 6.56, NNT 3) 5