Fungus

Tinea Corporis

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Tinea Corporis, Tinea Circinata, Ringworm

  • Etiology
  1. Trichophyton rubrum
  2. Epidermophyton floccosum
  3. Trichophyton tonsurans
  4. Trichophyton mentagrophytes
  5. Microsporum canis
  • Risk Factors
  1. Immunocompromised patients
  2. Allergic dermatitis and other causes of disrupted skin
  3. Genetic predisposition
  • Pathophysiology
  1. Infection
    1. Exposure to contaminated soil
    2. Exposure to infected people (e.g. Tinea Corporis Gladiatorum)
    3. Exposure to infected animals (e.g. dogs, cats, rabbits, rodents)
      1. Will appear on dog skin as red lesions with Alopecia and crusting
      2. Typically Microsporum canis
  2. Growth and transmission facilitating factors
    1. Warm and moist environments (showers and pools)
    2. Shared towels or clothing
  • Signs
  1. Location: Glabrous skin (excludes palms, soles, groin)
  2. Characteristics
    1. Round, erythematous, Scaling, pruritic Plaques
    2. Annular Lesion (hence the name Ringworm)
      1. Raised, advancing border
      2. Plaque with central clearing
        1. No central clearing after Corticosteroid use
    3. Postinflammatory pigmentation changes
  • Precautions
  1. Widespread Ringworm suggests underlying disease
  • Lab
  1. Potassium Hydroxide (KOH 20%)
    1. Scrape from active border
  2. Chlorazol black
    1. Highlights fungal hyphae
  3. Fungal Culture
    1. Suspected dermatophyte infection despite negative KOH
    2. Dermatophyte testing medium (DTM)
  4. Biopsy
    1. PAS stain will show hyphae in Stratum Corneum
  • Differential Diagnosis
  • Management
  1. Prevent re-infection (see pathophysiology above)
  2. Topical Antifungal applied twice daily for 2-3 weeks
    1. Technique
      1. Apply to infected and normal skin 2 cm beyond affected area
      2. Continue for 7 days after symptom resolution
    2. First line: Imidazoles (e.g. Clotrimazole)
    3. Refractory cases: Naftin, Lamisil, Loprox, Mentax
  3. Systemic Antifungal
    1. Indications
      1. Immunocompromised patient
      2. Disabling or widespread lesions
      3. Chronic infection
      4. Hyperkeratotic area involvement (palms or soles)
    2. Duration
      1. Start with 2-4 week course
      2. Consider extending prescription for additional 2-4 week course
    3. Preparations
      1. Terbinafine 250 mg orally daily
      2. Fluconazole 150 mg orally once per week
      3. Itraconazole (Sporanox)
      4. Griseofulvin 0.5-1.0 grams per day
      5. Ketoconazole 200 mg orally daily
        1. Indicated only for severe, refractory cases due to Ketoconazole hepatotoxicity
        2. If Ketoconazole is used, requires Liver Function Tests at baseline and again weekly
  • Complications
  1. Deep follicular Tinea Infection (Majocchi's Granuloma)
    1. Complication of Topical Corticosteroid use
    2. More commonly affects women, and most often on legs