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Pseudonits or Hair Casts

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Case Presentation

A 34-year old female with an unremarkable medical history presented with a 3-month history of scalp pruritus. Physical examination revealed small whitish lesions resembling nits, abundant on one dreadlock. Trichoscopy showed many whitish, tubular and non-adherent structures on the hair shafts ( Figure 1 ). There was no evidence of nits or lice on the rest of the scalp.

Figure 1 .

Trichoscopy reveals pseudonits.

Teaching Point

Pseudonits, hair casts, or keratin cysts are white objects that easily move along the hair. There are 2 types: (1) parakeratotic, associated with seborrheic dermatitis, psoriatic or excessive traction, and (2) peripilar, the pathogenesis of which is not clear but is more frequent in young women. Trichoscopy findings include whitish cylindrical structures around the hair shaft. Nits (main differential) present brown ovoid structure with a curved end (vital) or translucent structure with a planar end (empty). Pseudonits are frequently misdiagnosed as pediculosis capitis; trichoscopy, then, is essential for differentiation, avoiding patient anxiety and unnecessary treatments.

References

  1. Trichoscopy in the differential diagnosis of pseudonits Lacarrubba F, Verzì AE, Micali G. Skin Appendage Disord.2019;5(3):142-145. CrossRef PubMed
  2. Adult onset hair casts: nits which do not itch! Lokhande AJ, Sutaria A. Int J Trichology.2017;9(2):70-72. CrossRef PubMed
  3. Hair casts or pseudonits França K, Tadeu Villa R, Rezende Silva I, Almedia Carvalho C, Bedin V. Int J Trichology.2011;3(2):121-122. CrossRef PubMed

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