Pili annulati under the electron microscope: a case report and literature review

We report a 32-year-old woman whose hair had exhibited a distinctive pattern of black and white streaks under natural light. She underwent trichoscopic photography and scanning electron microscopy, leading to the identification of pili annulati (PA). Trichoscopic photography revealed that the hair shafts were uniformly thick, with a pattern of alternating light and dark bands resembling beads. The scanning electron micrograph depicted a rough and cracked surface of the hair stem, with many grooves clearly visible. And numerous air bubbles of varying sizes were observed within the hair cortex.