A hair shaft defect where hairs fracture at weak points, causing breakage and fraying.
Trichorrhexis nodosa is a structural hair shaft problem. Under magnification, the shaft can look frayed or brush-like at points of breakage. It may be inherited, but it is more often acquired from physical or chemical damage such as heat styling, bleaching, harsh brushing, tight hairstyles or repeated trauma. Patients may describe hair that will not grow past a certain length. Management focuses on identifying the cause of damage and reducing breakage rather than treating the follicle itself.
DermNet defects of the hair shaft: https://dermnetnz.org/topics/defects-of-the-hair-shaft ; DermNet trichoscopy of genetic hair shaft disorders: https://dermnetnz.org/topics/trichoscopy-of-genetic-hair-shaft-disorders