Clinical and molecular delineation of classical-like Ehlers–Danlos syndrome through a comprehensive next-generation sequencing-based screening system

Classical-like Ehlers–Danlos syndrome (clEDS) is an autosomal recessive disorder caused by complete absence of tenascin-X resulting from biallelic variation in TNXB. Accurate detection of TNXB variants is challenging because of the presence of the pseudogene TNXA, which can undergo non-allelic homologous recombination. Therefore, we designed a genetic screening system that is performed using similar operations to other next-generation sequencing (NGS) panel analyses and can be applied to accurately detect TNXB variants and the recombination of TNXA-derived sequences into TNXB. We also analyzed the levels of serum form of TNX (sTNX) by Western bot and LC/MS/MS. Using this system, we identified biallelic TNXB variants in nine unrelated clEDS patients. This report is the first to apply an NGS-based screening for TNXB variants and represents the third largest cohort of clEDS.