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Updated: Feb 11 2020

Tinea Capitis

  • Snapshot
    • A 7-year-old previously healthy boy is brought to the pediatrician with a pruritic scalp and patchy hair loss. His mother reports a close friend at school recently had similar symptoms. Physical exam shows scaly patches with alopecia and black dots. Potassium hydroxide (KOH) preparation shows fungal hyphae around hair follicles.
  • Introduction
    • Clinical definition
      • superficial fungal skin infection of the scalp
    • Epidemiology
      • demographics
        • most common in pre-pubertal boys
        • more common in African Americans
      • location
        • on the scalp ("capitis" = "head")
    • Etiology
      • infectious agents are fungi called dermatophytes, including
        • Trichophyton
        • Microsporum
      • acquired through direct contact with the fungus
        • e.g., shared combs and hats
    • Pathogenesis
      • dermatophytes live only in keritinized tissues (hair, skin, and nails)
      • symptoms result from host's innate immune response
    • Prognosis
      • excellent since most cases resolve with treatment
  • Presentation
    • Symptoms
      • itchiness
      • hair loss
    • Physical exam
      • single or multiple scaly patches on the scalp
      • alopecia with small black dots from broken-off hairs
      • cervical lymphadenopathy
      • less common
        • kerion
          • inflammatory plaque with drainage and crusting
        • favus
          • perifollicular erythema progresses to yellow cupping
  • Studies
    • Labs
      • potassium hydroxide (KOH) prep
        • used on hairs plucked from affected areas
          • outer hair shaft - Microsporum
          • inner hair shaft - Trychophyton
      • Wood lamp
        • ultraviolet A (UVA) light
          • if hair fluoresces
            • Microsporum spp. is the cause
          • if hair does not fluoresce
            • probable cause is Trichophyton spp.
    • Culture
      • rarely needed
      • can give definitive diagnosis
    • Diagnostic criteria
      • diagnosis typically made by physical exam
  • Differential
    • Alopecia areata
      • autoimmune form of hair loss
      • presents with patchy alopecia with black dots and without scaling
    • Seborrheic dermatitis
      • presents with diffuse scaling on the scalp with erythema and pruritis
    • Psoriasis
      • presents with scaly and erythematous plaques that are well-demarcated
  • Treatment
    • Conservative
      • management of close contacts
        • indication
          • when multiple children are in the home
        • treatments
          • use of antifungal shampoo by all house members
          • avoid sharing and clean hair clippers, combs, and hats
    • Medical
      • oral antifungals
        • indication
          • when diagnosis is made by physical exam and before culture results are available
        • medications
          • griseofulvin
            • mechanism of action
              • inhibits fungal mitosis and binds to keratin
          • terbinafine
            • mechanism of action
              • inhibits fungal cell membrane ergosterol synthesis
  • Complications
    • May progress to kerion or favus
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