Diagnosis of fungal scalp infection

Diagnosis

Diagnosis of tinea capitis should be established by clinical inspection as well as laboratory diagnostic tests whenever possible.

• clinical diagnostic aids
  • Wood's lamp
    • ectothrix Microsporum species demonstrate bright green fluorescence of infected hairs under Wood's lamp examination
      • may help in differentiating from nonfluorescent Trichophyton infection (exception: T. schoenleinii can fluoresce dull green)
    • value is limited due to the current predominance of nonfluorescing species of Trichophyton
      
      
  • dermoscopy
    • black dot hair stubs may be visualized more clearly
    • 'comma-shaped' hairs have been described in white children with ectothrix infection whereas corkscrew hairs have been reported in Afro-Caribbean children with tinea capitis (1,2)
      
      
• laboratory diagnosis
  • suspected tinea capitis lesions should be sampled by plucking hairs, using a blunt scalpel to remove hair and scalp scale, or by taking scalp brushings
  • microscopic examination
    • microscopy should be carried out on all scalp scrapings and plucked hairs, by mounting in 10-30% potassium hydroxide with or without calcofluor, and examination by light or fluorescence microscopy
    • presence of hyphae and/or arthroconidia should be reported.
  • culture
    • all specimens should be cultured on Sabouraud agar with at least one agar plate containing cycloheximide to inhibit non-dermatophyte mould growth
    • any dermatophytes growing should be identified and reported (1,2)

Reference:

1. Fuller LC et al. British Association of Dermatologists' guidelines for the management of tinea capitis 2014. Br J Dermatol. 2014;171(3):454-63.
2. Bennassar A, Grimalt R. Management of tinea capitis in childhood. Clin Cosmet Investig Dermatol. 2010;3:89-98