FMR1 and mitral valve prolapse: The phenotype and dysmorphology of FXS are related to a deficit in the FMR protein (FMRP), and this is typically manifested by a long narrow face, large, wide and prominent ears, a high arched palate, and features of a connective tissue disorder, such as hyperextensible finger joints, pectus excavatum, flat feet, hernias, soft skin and mitral valve prolapse [35], as well as low muscle tone and pubertal macro-orchidism (enlarged testicles) in males [52,53].