How is in vivo hair invasion characterized in the pathophysiology of tinea capitis (scalp ringworm)?

Updated: Feb 21, 2020
  • Author: Marc Zachary Handler, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Three types of in vivo hair invasion are recognized.

Ectothrix invasion is characterized by the development of arthroconidia on the exterior of the hair shaft. The cuticle of the hair is destroyed, and infected hairs usually fluoresce a bright greenish-yellow color under a Wood lamp ultraviolet light. Common agents include Microsporum canis, Microsporum gypseum, Trichophyton equinum, and Trichophyton verrucosum. [2]

Endothrix hair invasion is characterized by the development of arthroconidia within the hair shaft only. The cuticle of the hair remains intact and infected hairs do not fluoresce under a Wood lamp ultraviolet light. All endothrix-producing agents are anthropophilic (eg, Trichophyton tonsurans, Trichophyton violaceum). [3]

Favus, usually caused by T schoenleinii, produces favuslike crusts or scutula and corresponding hair loss.


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