II. Etiology
- Trichophyton rubrum
- Epidermophyton floccosum
- Trichophyton tonsurans
- Trichophyton mentagrophytes
- Microsporum canis
III. Risk Factors
- Immunocompromised patients
- Allergic dermatitis and other causes of disrupted skin
- Genetic predisposition
IV. Pathophysiology
- Infection
- Exposure to contaminated soil
- Exposure to infected people (e.g. Tinea Corporis Gladiatorum)
- Exposure to infected animals (e.g. dogs, cats, rabbits, rodents)
- Will appear on dog skin as red lesions with Alopecia and crusting
- Typically Microsporum canis
- Growth and transmission facilitating factors
- Warm and moist environments (showers and pools)
- Shared towels or clothing
V. Signs
- Location: Glabrous skin (excludes palms, soles, groin)
- Characteristics
- Round, erythematous, Scaling, pruritic Plaques
- Annular Lesion (hence the name Ringworm)
- Raised, advancing border
- Plaque with central clearing
- No central clearing after Corticosteroid use
- Postinflammatory pigmentation changes
VI. Precautions
- Widespread Ringworm suggests underlying disease
VII. Lab
-
Potassium Hydroxide (KOH 20%)
- Scrape from active border
- Chlorazol black
- Highlights fungal hyphae
-
Fungal Culture
- Suspected dermatophyte infection despite negative KOH
- Dermatophyte testing medium (DTM)
- Biopsy
- PAS stain will show hyphae in Stratum Corneum
VIII. Differential Diagnosis
- See Annular Lesion
- Pityriasis Rosea (especially the herald patch)
- Nummular Eczema (Atopic Dermatitis)
- Drug allergy or Fixed Drug Eruption
- Guttate Psoriasis (annular Psoriasis)
- Erythema Annulare Centrifugum
- Erythema Multiforme
- Contact Dermatitis
- Discoid Lupus
- Bowen's Disease
- Parapsoriasis
- Mycosis Fungoides (Cutaneous T Cell Lymphoma)
- Granuloma Annulare
- Secondary Syphilis
- Seborrheaic dermatitis
IX. Management
- Prevent re-infection (see pathophysiology above)
-
Topical Antifungal applied twice daily for 2-3 weeks
- Technique
- Apply to infected and normal skin 2 cm beyond affected area
- Continue for 7 days after symptom resolution
- First line: Imidazoles (e.g. Clotrimazole)
- Refractory cases: Naftin, Lamisil, Loprox, Mentax
- Technique
- Systemic Antifungal
- Indications
- Immunocompromised patient
- Disabling or widespread lesions
- Chronic infection
- Hyperkeratotic area involvement (palms or soles)
- Duration
- Start with 2-4 week course
- Consider extending prescription for additional 2-4 week course
- Preparations
- Terbinafine 250 mg orally daily
- Fluconazole 150 mg orally once per week
- Itraconazole (Sporanox)
- Griseofulvin 0.5-1.0 grams per day
- Ketoconazole 200 mg orally daily
- Indicated only for severe, refractory cases due to Ketoconazole hepatotoxicity
- If Ketoconazole is used, requires Liver Function Tests at baseline and again weekly
- Indications
-
Return to School and sports
- May Return to School and daycare once treatment is started
- Avoid sports with person-to-person contact (e.g. wrestling) for 72 hours after treatment starts (or cover wound)
X. Complications
- Deep follicular Tinea Infection (Majocchi's Granuloma)
- Complication of Topical Corticosteroid use
- More commonly affects women, and most often on legs