Peripilar hair casts

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Clinical presentation

A 7-year-old girl who wore a tight ponytail every day presented at our dermatology clinic with whitish particles bound to the hairs of her scalp, a problem that had existed for a number of months (Fig 1). Pediculosis capitis was suspected by the physicians who attended her at another clinic, and permethrin shampoo was prescribed on several occasions. However, no improvement was seen.

Dermoscopic appearance

Polarized light dermoscopy revealed small, bright, long and tubular, whitish structures of 1 to 2 mm surrounding multiple hair shafts in distal, medial, and proximal positions (Fig 2). They could be easily moved along the affected hairs.

Key message

The child was diagnosed with peripilar keratin casts, which are commonly misidentified as head louse eggs. However, the latter appear as round particles bound to the sides of the hair shafts, whereas peripilar casts appear as cylindrical tubular

References (2)

Cited by (6)

  • Alternative uses of dermoscopy in daily clinical practice: An update

    2018, Journal of the American Academy of Dermatology
    Citation Excerpt :

    The hair follicles appear horizontally and radially oriented, configuring a starburst pattern of the hair follicles that is probably due to aberrant shearing forces occurring early at some point of follicle development and forcing them to bend;170 moreover, black dots may sometimes be detected. A total of 8 single cases have been reported.171-178 Dermoscopy shows cylindric white-yellowish masses surrounding the hair shafts that can be detected in both primary idiopathic and secondary forms from mechanical traction or scalp conditions such as psoriasis, atopic dermatitis, and pemphigus vulgaris.

  • Diagnostic protocol for alopecia

    2018, Medicine (Spain)
  • Head Louse Caught in the Act

    2019, Indian Journal of Pediatrics

Publication of this article was supported by 3Gen Inc.

Funding sources: None.

Conflicts of interest: None declared.

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