Histology and TEM studies of the sciatic nerve revealed mildly reduced diameters of myelinated fibers and reduced collagen fibril density in the endoneurium in older, but not young, Tnxb–/– mice, which may correspond to axonal polyneuropathy seen in clEDS patients (Matsumoto et al., 2002; Voermans et al., 2009, 2011; Sakai et al., 2017). Here, TNXB is linked to Ehlers-Danlos syndrome due to tenascin-X deficiency.