A 28-year-old woman with diabetes presents with erythematous, scaly patches on the dorsal surfaces of both hands and forearms. Fungal culture confirms *Trichophyton mentagrophytes*. Regarding tinea corporis, all of the following are true EXCEPT:

Explanation

## Tinea Corporis — Clinical Presentation & Management ### Correct Statements (Options 0, 1, 3) **Key Point:** Tinea corporis is a dermatophyte infection of the trunk and extremities, classically presenting with annular (ring-shaped) lesions with central clearing and an active, raised, scaly border — the hallmark "ringworm" appearance. **High-Yield:** Common sites of tinea corporis include: - Trunk (most common) - Dorsal hands and feet - Forearms and legs - Face (less common; often misdiagnosed as eczema) **Clinical Pearl:** Risk factors for tinea corporis include: - Warm, humid climate - Poor hygiene - Contact with infected animals or persons - **Diabetes mellitus** — hyperglycemia impairs neutrophil function and cell-mediated immunity, predisposing to severe or recurrent fungal infections - Immunosuppression (HIV, corticosteroids) ### Why Option 2 is INCORRECT **Warning:** Topical antifungals are **NOT ineffective** in tinea corporis — they are the standard first-line treatment and are highly effective for localized lesions. **High-Yield:** Treatment algorithm for tinea corporis: - **Localized lesions (< 5 cm or few lesions):** Topical azole (clotrimazole, miconazole) or allylamines (terbinafine cream) for 2–4 weeks - **Extensive lesions (> 5 cm, multiple sites, or failed topical therapy):** Systemic therapy (terbinafine 250 mg daily for 2–4 weeks, or itraconazole 200 mg daily for 1–2 weeks) - **Severe inflammation or immunocompromised:** Systemic therapy ± short course of topical corticosteroid ### Management Decision Tree ```mermaid flowchart TD A[Tinea corporis diagnosed]:::outcome --> B{Extent of lesions?}:::decision B -->|Localized < 5 cm| C[Topical azole or terbinafine]:::action B -->|Extensive or multiple| D[Systemic antifungal]:::action C --> E[2-4 weeks topical]:::action D --> F[Terbinafine 250 mg daily x 2-4 weeks]:::action D --> G[Itraconazole 200 mg daily x 1-2 weeks]:::action E --> H[Cure expected]:::outcome F --> H G --> H ``` ### Tinea Corporis vs. Other Annular Lesions | Feature | Tinea Corporis | Pityriasis Rosea | Erythema Migrans | | --- | --- | --- | --- | | **Scale** | Present (on border) | Fine, collarette | Absent | | **KOH mount** | Septate hyphae | Negative | Negative | | **Central clearing** | Yes | Yes | Yes (target lesion) | | **Pruritus** | Variable | Mild | Usually absent | | **Causative agent** | Dermatophyte | Unknown (viral?) | *Borrelia burgdorferi* | [cite:Park 26e Ch 16]