Pili Annulati: A case series and proposal for classification

Pili annulati is an autosomal dominant hair shaft disorder mapped to chromosome 12q24.33 and classified among hair shaft disorders without fragility. It is characterized by a shiny appearance with alternating light and dark bands and typically affects the scalp, as well as axillary, beard, and pubic hair. Trichoscopy reveals hair shafts with alternating white and dark bands involving approximately 50% to 100% of the shaft thickness. Light microscopy and transmission electron microscopy are useful diagnostic tools. We report a case series of seven patients diagnosed with pili annulati via clinical and trichoscopic evaluation. Of these cases, one patient exhibited unusual involvement of the eyebrows and eyelashes, another presented with a distinct patch of heterochromia, and the remaining five demonstrated diffuse involvement confined to the scalp. Although traditionally considered a rare condition, the prevalence of pili annulati may be underestimated. Therefore, proficiency in recognizing its characteristic clinical and trichoscopic features is essential for an accurate and timely diagnosis.