A previously undescribed hereditary hair anomaly (pseudo-monilethrix)

Abstract

SUMMARY A new term ‘pseudo‐monilethrix’ is suggested for an unusual form of ‘beaded’ hair, found in many members of a large Caucasoid family. The abnormality bears a resemblance to classical monilethrix but is not the same condition. Other associated anomalies are formes frustes of pili torti and trichorrhexis nodosa. These disorders are traced through four generations and appear to have been inherited as an autosomal dominant trait. The clinical features and prognosis are discussed and the results of the examination of hairs under the light and scanning electron‐microscopes are recorded.

The genetics of hair shaft disorders

“…PT has been reported in association with other genetic hair shaft abnormalities 32,98,105,127,[183][184][185][186][187][188][189] (Table IV).…”

Hair Disorders

“…It has been reported to occur in association with monilethrix [123] , pseudomonilethrix [124] , woolly hair [125] , longitudinal grooving [126] , trichorrhexis nodosa [59] and trichorrhexis invaginata [138] . In the classic Ronchese type of pili torti, the inheritance is usually autosomal dominant, but autosomal recessive and sporadic inheritance have also been reported [122,128 -130] .…”

“…Pseudomonilethrix is microscopic irregular beading along the hair shaft as opposed to the regular beading seen in monilethrix [124] (Fig. 148.19 ).…”

“…148.19 ). Although it has been reported in patients with fragile hair [124,142] , the appearance of pseudomonilethrix can be produced in normal hairs by compressing two hairs together between two glass slides [143,144] . It is likely that the nodes in pseudomonilethrix are artefactual [57] .…”

A practical, algorithmic approach to diagnosing hair shaft disorders

“…The hair breaks spontaneously or as a result of friction. A hair mount shows the distinctive ''nodes'', or wide segments, which have the diameter of normal hair and are medullated; these alternate with the ''internodes'' or constrictions that have no medulla and are the sites of fracture 69 (Fig. 12).…”