diagnosis
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tinea corporis annular erythematous plaque back ringworm
Based on analysis of both images and the textbook findings, here is the clinical assessment:
Diagnosis: Tinea Corporis (Dermatophytosis / "Ringworm")
Clinical Features Supporting This Diagnosis
Image 1 (mid-back):
- Large, well-demarcated annular plaque with erythematous, slightly raised, scaly border
- Central clearing — characteristic centrifugal spread
- Fine peripheral scaling at the active edge
- Location on trunk (common site)
Image 2 (axilla/shoulder):
- Curved erythematous arc with a scaling, advancing border
- Violaceous-brown hue consistent with darker skin phototype
- Perimeter involvement near axilla — a warm, moist site favoring dermatophytes
Pathophysiology
Tinea corporis is caused by dermatophyte fungi (Trichophyton, Microsporum, Epidermophyton species) infecting the stratum corneum. The lesion starts as a papule and expands centrifugally, producing the classic ring morphology with a trailing or leading scale at the advancing border. — Fitzpatrick's Dermatology, Vol. 1
Key Differential Diagnoses to Exclude
| Condition | Distinguishing Feature |
|---|---|
| Erythema annulare centrifugum (EAC) | "Trailing scale" on inner edge; often no pruritis; associated with systemic triggers |
| Granuloma annulare | Flesh-colored, non-scaly; no epidermal change |
| Nummular eczema | Coin-shaped, intensely pruritic, oozing/crusting |
| Pityriasis rosea | Herald patch; collarette scale; follows Langer's lines |
| Psoriasis (annular) | Thick silvery scale; other psoriatic features |
Recommended Workup
- KOH preparation of scale scraping from the advancing border — most rapid confirmatory test
- Fungal culture if KOH equivocal
- Wood's lamp (limited utility for Trichophyton species)
Management
- Topical antifungals (first-line for localized disease): Terbinafine 1% cream once daily × 2 weeks, or Clotrimazole/Miconazole twice daily × 4 weeks
- Oral therapy (large/extensive/recalcitrant lesions): Terbinafine 250 mg/day × 2–4 weeks or Griseofulvin
- Treat any concurrent tinea pedis/unguium to prevent recurrence
- Avoid sharing towels, clothing; keep skin dry
Note: Given the involvement of multiple body sites (back and axilla), oral antifungal therapy may be preferred over topical alone. A formal clinical examination and KOH confirmation is recommended before initiating treatment.
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