Hair Biology and Hair Loss Disorders: An Update and New Concepts

In the past two decades, significant advancements have been made in understanding hair follicular biology, which has improved knowledge of the etiopathogenesis and pathophysiology of hair loss disorders such as scarring alopecia, alopecia areata, androgenetic alopecia, and congenital hair loss diseases. Key discoveries include the identification of epithelial stem cells in the bulge area of hair follicles, the molecular signature of hair follicle components, the concept of hair follicle immune privilege, and the mechanisms of epithelial-mesenchymal interaction in hair morphogenesis and cycling. Despite these advances, challenges remain, such as determining the triggers for autoimmunity in alopecia areata. The complexity of hair follicle physiology and microanatomy, limited treatment options for certain types of alopecia, and a lack of interaction among hair specialists may contribute to a lack of familiarity with hair diseases among dermatologists. This special issue of the Journal of Dermatology aims to provide a comprehensive overview of recent advances in the understanding and management of hair loss disorders, with the goal of keeping dermatologists up to date with the latest knowledge in the field.