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A young girl presented for evaluation of hair loss. The mother stated that the patient was born with normal-appearing dark hair that fell out days after birth. This was replaced with “peach fuzz,” with no subsequent regrowth of normal hair. She denied pruritus. Family history was significant for similar hair loss in the patient’s maternal grandmother and maternal cousin. The patient had otherwise normal development. On physical examination, short, brittle terminal hairs of varying lengths covered the entire scalp. Follicular hyperkeratosis and perifollicular erythema were present, most prominently on the parietal and occipital scalp (Figure, A). Mild perifollicular keratotic papules were noted on the posterior upper arms. Teeth and nails showed no abnormalities. Her eyebrows and lashes were not affected. Results of trichography are shown (Figure, B).
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The term monilethrix comes from a combination of the Latin word for necklace (monile) and the Greek word for hair (thrix), referring to the alternating thin and thick areas of the hair shaft that cause the distinctive, beaded appearance on light microscopy. Monilethrix is an alopecia characterized by hair shaft fragility, hair loss, and follicular hyperkeratosis that is worse on the occipital scalp. Keratosis pilaris of the neck and arms may also be seen.1 Although generally an autosomal dominant disorder with incomplete penetrance resulting from mutations on chromosome 12q13 affecting type II keratin genes such as hHb1 (KRT81 [OMIM 602153]), hHb3 (KRT83 [OMIM 602765]), or hHb6 (KRT86 [HGNC 6463]), some autosomal recessive cases have been reported, associated with mutations in desmoglein 4.1- 3 Affected individuals typically have normal neonatal lanugo hair on the scalp at birth, which is shed and replaced with brittle, short hair within the first months of life. Severity varies substantially among cases, from a limited occipital distribution to diffuse involvement of eyebrows, eyelashes, secondary sexual hair, teeth, and nails.4 The diagnosis of monilethrix was confirmed in this patient after pulling several scalp hairs at the root and examining on ×4 microscopy. The characteristic beaded appearance of the hair shaft was noted (Figure, B).
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Corresponding Author: Allison R. Cruse, MD, Department of Dermatology, University of Mississippi Medical Center, 2500 N State St, Jackson, MS 39216 (firstname.lastname@example.org).
Published Online: December 4, 2017. doi:10.1001/jamapediatrics.2017.4340
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient’s mother for granting permission to publish this information. David Marbury, MD, Department of Pathology, University of Mississippi, Jackson, photographed the light microscopy image. He was not compensated for this contribution.
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