title: [Hair cylinders].
abstract: Hair casts (peripilar keratin casts) of two girls are investigated by electron microscopy. The 31 cases of hair casts so far known are briefly summarized. The etiology seems to be heterogeneous. The ultrastructural study of the casts reveals three layers. Two of them can easily be interpreted as internal root sheet, the third with parts of the outer root sheet, rather than with parts of the epithelium of the follicular infundibulum, as was suggested by Kligman in 1957.
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006197:Hair / Q000473:pathology / Q000648:ultrastructure; D006201:Hair Diseases / Q000473:pathology*; D006801:Humans; D008854:Microscopy, Electron
vernacular_title: Haarzylinder.