TNXB and Ehlers-Danlos syndrome: Useful investigations to support molecular testing include immunoassay for serum dosage of tenascin X in TNXB-related classic-like EDS, dermis ultrastructural analysis in classical, dermatosparaxis and arthrochalasis subtypes, gel electrophoresis analysis from skin fibroblasts for collagen I- and III-related phenotypes, and quantification of deoxypyridinoline and pyridinoline crosslinks in urine with high-performance liquid chromatography in kyphoscoliotic EDS.1