Fig. 7. Keratin rings are composed of small fragments of keratin. DM-EBS keratinocytes were stretched for 120 minutes and prepared for transmission electron microscopy. Whorls and rings of keratin filament bundles were frequently observed in the cell periphery (A). Solid aggregates of keratin, reminiscent of the diagnostic hallmark of DM-EBS, were also seen (B,C). Keratin rings were observed and the irregular form of the rings suggests they may be formed of annealed stretches of filament bundles complexed with some associated proteins (D,E). In some cases these structures dipped in or out of the plane of section (E,). Bars, 500 nm.