A review of genotrichoses and hair pathology associated with inherited skin diseases.

Genetic hair disorders, also known as genotrichoses, are characterized by abnormalities of hair structure, growth, or differentiation, giving rise to a spectrum of phenotypes such as hypertrichosis, hypotrichosis and atrichia. These disorders may present as isolated phenotypes or be part of more complex phenotypes including abnormalities in skin or other organs. Genetic discoveries for hair disorders have been recently augmented with the advent of next-generation sequencing (NGS) technologies. We reviewed the literature and summarised disease-gene associations for inherited hair disorders, as well as genodermatoses presenting with hair abnormalities discovered by NGS technologies. We identified 28 non-syndromic hair disorders, involving 25 individual genes and four unidentified genes. We have also discovered that approximately 30% of all genodermatoses that were identified by NGS approaches demonstrated hair abnormalities as part of their phenotype. This review underscores the huge impact of NGS technologies in disclosing the genetics of hair disorders and the potential the discoveries provide for future translational research and new therapies.