Hair Disorders
This chapter is a comprehensive review of potential causes of alopecia or hair overgrowth that physicians may see in the paediatric population. It begins with an overview of the embryology and cycling of hair and then reviews the specifics of what is necessary to clinically diagnose a given hair disorder, i.e. the overall physical examination with particular reference to that of the scalp, microscopic evaluation of pulled or plucked hairs, the dermatoscopic examination and how and when to do a scalp biopsy. Hair loss is then addressed with various sections on abnormalities in the initiation of hair growth (examples include ectodermal dysplasias, follicular hyperkeratosis with scalp alopecia, syndromes with hypotrichosis); hair shaft abnormalities, including those presenting with hair breakage (examples include trichorrhexis nodosa, trichothiodystrophy, trichorrhexis invaginata, pili torti, monilethrix, etc.), hair shaft abnormalities associated with unruly hair (examples include uncombable hair syndrome, woolly hair, Marie–Unna type of hereditary hypotrichosis), and miscellaneous hair shaft abnormalities; hair loss due to abnormal cycling (examples include anagen and telogen effluvium, loose anagen syndrome); miniaturization of hair (androgenetic alopecia) and focal scarring and nonscarring causes of alopecia. The chapter then addresses causes of diffuse and local hypertrichosis. In each presentation of a type of hair loss or hypertrichosis, the clinical presentation, potential genetic association (if known) and available treatments are reviewed. Common conditions such as alopecia areata, trichotillomania and scalp infections/infestations are covered in other chapters.
