Monilethrix Workup

Updated: May 28, 2019
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Workup

Other Tests

Light microscopy, with macroscopic examination, aids in diagnosis. The hair shaft has regular, elliptical, fusiform, or spindle-shaped swellings (nodes) that are 0.7-1.0 mm in diameter and separated by constricted internodes. The nodes have the diameter of normal hair and are medullated, whereas the internodes have no medulla and are the sites of fracture. Pigment is present in both segments.

Scanning electron microscopy may reveal useful findings. All nodes demonstrate normal or worn transverse cuticular scales. Internodes show a dense longitudinal pattern of scales and ridging.

Dermoscopy can be used as a tool for rapid diagnosis of monilethrix. [22, 23, 24] It may show hair shafts with uniform elliptical nodes and intermittent constrictions, hairs bent regularly at multiple locations, and a tendency to fracture at constriction sites. The hair may be of varying lengths, with multiple shafts broken. [25] Hair with normal morphology may be interspersed within beaded hair. Scalp hair may have white dots and a honeycomb pigment network. The forearm hair may appear to be normal but, with dermoscopy, beaded short hairs may be evident. Videodermoscopy of hair (trichoscopy) may be similarly used. [26]

Note the images below.

Photomicrograph shows the regular nodes and intern Photomicrograph shows the regular nodes and internodes of the hair shaft in monilethrix, or pili moniliformes (original magnification X200).
Photomicrograph shows the regular nodes and intern Photomicrograph shows the regular nodes and internodes of the hair shaft in monilethrix, or pili moniliformes (original magnification X200).
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Histologic Findings

Landau et al recently described an easy way to diagnose severe neonatal monilethrix. [27] One can scrape the scalp with a glass slide, collect epidermal cells and rudimentary hair fragments, and examine the unstained specimen by using a microscope. One should find single or paired beads of typical monilethrix hair.

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