tinea%20capitis
TINEA CAPITIS
Tinea capitis  is a contagious dermatophytosis affecting the hair shaft and follicles of the scalp, eyebrows and eyelashes.
It is most common in the crowded areas as infection originates from contact with a pet or an infected person and asymptomatic carriage persists indefinitely.
It primarily affects children 3-7 years of age.
The causative agents are the genus Trichophyton and Microsporum.
Cardinal clinical feature is the combination of inflammation with hair breakage and loss.

Diagnosis

  • All specimens obtained (scalp scrapings, hair follicles) should undergo microscopy & culture, w/ causative organism identified

Laboratory Tests

Microscopy

  • Provides the most rapid means of diagnosis but may not always be positive in affected patients
  • Scalp scales &/or hair are mounted in 10-30% potassium hydroxide (KOH) solution, gently heated & viewed under light or flourescence microscope
  • Positive results reveal hairs and scales invaded by spores &/or hyphae

Causative Agents

  • Large-spored endothrix pattern chains of large spores w/in hair (Trichophyton tonsurans, T violaceum)
  • Large-spored ectothrix (T verrucosum, T mentagrophytes)
  • Small-spored ectothrix randomly arranged in masses inside & on the surface of the hair shaft (Microsporum canis, M audouinii)

Dermoscopy

  • A noninvasive in vivo imaging technique that may aid in the diagnosis of Tinea capitis, especially in patients w/ black dot pattern

Culture

  • Allows accurate identification of organism but results may take up to 4 weeks
  • Use of Sabouraud agar w/ 1 or more plates w/ cycloheximide is recommended
  • Results may be positive even when microscopy is negative
  • Necessary in hair fungal infections to identify the source of infection & verify the infecting species

Wood’s Light Exam

  • Useful for certain ectothrix infections (eg M canis, M audouini, M rifalieri)
  • If present, will cause hair to fluoresce bright green
  • T tonsurans which causes most Tinea capitis does not fluoresce
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