ABSTRACT
This chapter discusses the main clinical and morphological diagnostic characteristics of hair dysplasias. Atypical pili torti has also been observed associated with Menkes’ syndrome or other hair dysplasias such as pili canaliculi and woolly hair. Pseudomonilethrix is a rare autosomal dominant defect characterized by hair fragility. Trichorrhexis invaginata includes both a ballooning distortion of the hair shaft as well as a chaliced deformation of the proximal hair shaft. Trichothiodystrophy is a complex syndrome due to a low content of sulfured compounds in the hair that leads to a specific hair dysplasia. Hair usually shows some little balls in the distal end. The more distal, the closer the little balls appear. The hair shaft breaks at these little balls and final end of the hair shaft bifurcates; consequently, the hair of the affected individuals shows trichoptilosis and trichorrhexis nodosa. Loose anagen hair is a hair dysplasia due to lack of adhesion of the hair shaft to the hair follicle.
