However, a subset of subjects with hypermobility EDS have been identified to have defects in TNXB, which encodes tenascin‐X (TNX), a large glycoprotein essential for the constitution of the extracellular matrix (ECM) (Burch et al., 1997; Merke et al., 2013; Morissette et al., 2015; Schalkwijk et al., 2001; Zweers et al., 2003). The gene discussed is TNXB; the disease is Ehlers-Danlos syndrome.