Disappearance of pili annulati following an episode of alopecia areata.

Pili annulati is a distinctive autosomal dominant hair shaft disorder that produces alternating light and dark bands that can give a spangled appearance to the hair. The literature contains three case reports of patients in whom the condition has disappeared following recovery from alopecia totalis. None of these reports contain a direct microscopic comparison of pre- and post-regrowth hairs. We report a 6-year-old girl who was first noted to have pili annulati at the age of 2 years and who developed alopecia totalis at the age of 3 years. When the hair regrew spontaneously, 18 months later, the pili annulati was no longer visible. Hair samples obtained before and after the episode of alopecia areata were compared by normal and cross-polarized light microscopy. While not apparent on careful clinical examination, banding was present on light microscopy in 20% of the hairs. Eighty per cent of the affected hairs displayed banding throughout their entire length. In contrast, prior to the episode of alopecia totalis, when the pili annulati was clearly visible, 50% of the hair obtained was banded on microscopy and 90% of the affected hairs showed banding throughout their microscopic length.