Indeed, disease-causing mutations in several ECM-related genes or enzymes involved in biosynthesis or processing of ECM proteins, cause a myriad of HCTDs, e.g., Ehlers–Danlos syndromes (EDS), Osteogenesis imperfecta (OI), Marfan syndrome (MFS), Loeys–Dietz syndromes (LDS), arterial tortuosity syndrome (ATS), and numerous skeletal dysplasias [9]. Here, MMRN1 is linked to Marfan syndrome.