Newly described weathering pattern in pili annulati hair shafts: A scanning electron microscopic study

Certain scalp hair shafts from 2 of 10 cases of pili annulati examined by s canning electron microscopy exhibited an unusual weathering pattern. The ma jority of affected hair shafts showed minor surface abnormalities at regula r intervals (nodes) associated with the underlying spaces. However, in a fe w examples, there was marked damage to the cuticle at the nodes exposing th e underlying cortex; in severe cases there was cracking of both cuticle and cortex. These damaged nodes were also associated with trichorrhexis nodosa -like breaks of the hair shaft. This study shows that the nodes in pili ann ulati may have some inherent weakness that could result in breaks in the ha ir shaft exposed to physical trauma.