CYP21A2 and congenital adrenal hyperplasia: Tenascin-X is a large extracellular matrix–forming glycoprotein, whose deficiency was firstly involved in the etiology of EDS in 1997, by the description of a novel contiguous gene syndrome combining congenital adrenal hyperplasia (CAH) and EDS, and due to the deletion of the CYP21A2 (OMIM 201910) and TNXB neighbouring genes [4].