Updated: 9/27/2017

Tinea Cruris

Topic
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Snapshot
  • A 17-year-old boy presents to his pediatrician for evaluation of a rash in his genital area. He reports that it is very itchy and started about 1 week ago. At school, he participates in multiple sports, including wrestling with practice 3 times a week. He admits that he doesn’t always wash his hands and often delays showering after practice. On physical exam, there are multiple 3-5 cm annular and pink plaques on inner thighs and groin. His scrotum is clear. He is given a topical treatment for his rash.
Introduction
  • Clinical definition
    • superficial fungal infection of the skin of the groin or inner thighs
      • a type of dermatophytosis
      • also known as jock itch
  • Epidemiology
    • incidence
      • 10-20% lifetime incidence
    • demographics
      • adolescent and adult males
      • adult females who are overweight or wear tight jeans
    • risk factors
      • close contact sports, such as wrestling
      • moist warm environment
      • immunocompromise
      • contact with infected animals
  • Etiology
    • dermatophytes
      • Trichophyton
        • most commonly Trichophyton rubrum
      • Microsporum
      • Epidermophyton
  • Pathogenesis
    • fungus infects superficial keratinized tissue and invades stratum corneum and terminal hair
  • Associated conditions
    • tinea pedis
      • often the source of infection
    • onychomycosis
  • Prognosis
    • responsive to topical treatment
Presentation
  • Symptoms
    • primary symptoms
      • itch
  • Physical exam
    • can have single or multiple lesions
    • well-demarcated annular patches or plaques with central clearing with
      • scaling
      • diffuse erythema
    • location
      • inner thighs or groin
        • spares scrotum and mucosa
Studies
  • KOH preparation
    • skin scrapings at active edge of lesion mixed with KOH
    • presence of hyphae indicates fungal infection
  • Wood lamp
    • indications
      • to rule out erythrasma
        • coral-red fluorescence
  • Diagnostic criteria
    • diagnosis usually based on clinical history and physical exam
Differential
  • Erythrasma
    • coral-red fluorescence under Wood lamp
  • Cutaneous candidiasis
Treatment
  • Medical
    • topical therapy
      • indication
        • localized lesions
      • drugs
        • terbinafine 1%
          • approved for patients 12 years of age and older
        • clotrimazole 1%
          • approved for patients 2 years of age and older
        • ketoconazole 2%
    • oral therapy
      • indications
        • widespread disease
        • refractory disease
      • drugs
        • terbinafine
        • griseofulvin
Complications
  • Secondary bacterial infection
 

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