Updated: 2/11/2020

Tinea Capitis

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Snapshot
  • Tinea CapitisA 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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