How is ectothrix infection in tinea capitis (scalp ringworm) defined?

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

Ectothrix infection is defined as fragmentation of the mycelium into conidia around the hair shaft or just beneath the cuticle of the hair, with destruction of the cuticle. Inflammatory tinea related to exposure to a kitten or puppy usually is a fluorescent small spore ectothrix. Some mild ringworm or prepubertal tinea capitis infections are of the ectothrix type, also termed the gray-patch type (microsporosis; see the image below). Some ectothrix infections involute during the normal course of disease without treatment. Depending on the extent of associated inflammation, lesions may heal with scarring.

Gray-patch ringworm (microsporosis) is an ectothri Gray-patch ringworm (microsporosis) is an ectothrix infection or prepubertal tinea capitis seen here in an African American male child. Gray patch refers to the scaling with lack of inflammation, as noted in this patient. Hairs in the involved areas assume a characteristic dull, grayish, discolored appearance. Infected hairs are broken and shorter. Papular lesions around hair shafts spread and form typical patches of ring forms, as shown. Culture from the lesional hair grew Microsporum canis.

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