Ivo, Catarina RodriguesFitas, Ana LauraMadureira, InêsDiamantino, CatarinaGomes, SusanaGonçalves, JoãoLopes, Lurdes2023-02-022023-02-022022-10-20J Pediatr Endocrinol Metab. 2022 Oct 20;36(1):81-85. doi: 10.1515/jpem-2022-0396. Print 2023 Jan 270334-018Xhttp://hdl.handle.net/10400.18/8493Case ReportsObjectives: Congenital Adrenal Hyperplasia (CAH) is a group of genetic diseases characterized by impaired cortisol biosynthesis. 95% of CAH cases result from muta tion in the CYP21A2 gene encoding 21-hydroxilase. TNX-B gene partially overlaps CYP21A2 and encodes a matrix protein called Tenascin-X (TNX). Complete tenascin defi ciency causes Enlers-Danlos syndrome (EDS). A mono allelic variant called CAH-X CH-1 was recently described, resulting from a CYP21A2 complete deletion that extends into the TNXB. This haploinsufficiency of TNX may be associated with a mild hypermobility form of EDS, as well as other connective tissue comorbidities such as hernia, cardiac defects and chronic arthralgia. Case presentation: We report four patients heterozygous for a CAH-X CH-1 allele that do not present clinical mani festations of the EDS. Conclusions: All CAH patients, carriers of these TNXA/ TNXB chimeras, should be evaluated for clinical manifes tations related to connective tissue hypermobility, cardiac abnormalities and other EDS features, allowing for better clinical surveillance managementengCAH-X SyndromeCYP21A2Tenascin-XTNXATNXBGenética HumanaDoenças Genéticasjournal article10.1515/jpem-2022-0396