Updated: 10/2/2017

Tinea Corporis

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Snapshot
  • An 11-year-old previously healthy girl presents with a circular lesion on her body. She does not report any itchiness or pain. Her mother reports that the patient's 8-year-old brother has had an itchy scalp and patchy hair loss over the last two weeks. On physical exam, the lesion appears with concentric rings, with scale on the periphery. The physician collects scrapings of the lesion and performs a potassium hydroxide preparation. Under microscopy, multiple septated hyphae are observed.
Introduction
  • Clinical definition
    • superficial fungal infection of the skin
    • "corporis" = "body"
      • affected areas include the trunk, legs, arms, and neck
      • does not include the feet, hands, groin, nails, and scalp
        • these tinea infections are classified differently
  • Epidemiology
    • demographics
      • most common in pre-adolescents
      • classically in athletes with skin-to-skin contact (wrestlers)
    • risk factors
      • exposure to an infected person or animal
      • may be acquired from tinea capitis
        • this is the most common cause in children
      • immunocompromised state
  • Etiology
    • dermatophyte fungal infection
      • most commonly from the
        • trychophyton and microsporum genera
          • trychophyton rubrum is the most common
    • caused by direct contact with the fungus
      • infection on another person or animal
        • especially kittens and puppies
      • infection from another location
        • e.g. tinea cruris, tinea pedis, etc.
  • Pathogenesis
    • infection of the epidermis
      • occasionally spreads to the hair follicles
  • Prognosis
    • excellent
      • most cases resolve with treatment
Presentation
  • Symptoms
    • single or multiple pruritic areas of rash
    • may be asymptomatic
  • Physical exam
    • begins as an erythematous, scaly patch or plaque in a circular or oval shape
    • spreads outward, with central clearing
    • sharply marginated
      • with a raised border that advances
    • multiple lesions may coalesce
    • may become extensive
      • should raise suspicion for immune compromise
    • may be inflammatory with significant erythema
      • more common in infection from animals
Studies
  • Labs
    • potassium hydroxide (KOH) prep
      • commonly done to confirm diagnosis
      • performed on scrapings from lesions 
      • will show characteristic segmented hyphae of dermatophytes
  • Culture
    • may be used for definitive diagnosis
Differential Diagnosis
  • Subacute cutaneous lupus erythematosus
    • will be erythematous, ring-shaped, scaly plaques on sun-exposed skin
  • Granuloma annulare
    • benign inflammatory condition
    • will have multiple erythematous plaques on the extremities
    • does not exhibit scaling
  • Pitariasis rosea
    • will show circular, erythematous lesions and may exhibit scaling
    • scale will appear as "collarette"
    • may show "christmas tree-like" distribution on back, following lines of tension
Treatment
  • Medical
    • topical antifungal 
      • medications
        • azoles
        • terbinafine
        • naftifine
        • note, topical nystatin is not effective against dermatophytes
      • mechanism of action
        • azoles
          • inhibit fungal cell membrane formation
          • disrupts biosynthesis of ergosterol
        • terbinafine
          • blocks fungal cell wall production
          • inhibits squalene epoxidase
    • systemic antifungal therapy
      • indication
        • extensive skin involvement
        • failure of topical therapy
      • medications
        • itraconazole
        • terbinafine
Prognosis, Prevention and Complications
  • Infection may be extensive in the setting of underlying immunodeficiency
    • e.g. HIV/AIDS, diabetes
 

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