Scanning electron microscopy comparing exclamation mark hairs in alopecia areata with normal hair fibres, mechanically broken by traction.

A scanning electron microscope was used to compare the distal ends of exclamation mark hairs from alopecia areata patients with the fracture surface of normal hair fibres, mechanically broken by traction. The exclamation mark hairs shows minimal damage to the cuticular cell pattern of the hair shaft. Where the cuticle was absent, cortex and medulla showed low-density features fanning out into a fringe-like structure at the distal ends. The fracture surfaces of normal hair fibres, mechanically broken by traction showed a markedly abnormal cuticular scale pattern, whereas the features of cortical and medullary tissue were normal. These morphological differences between the fracture surface of exclamation mark hairs and normal hair fibres, mechanically broken by traction, may enhance our understanding of the pathogenesis of alopecia areata.