FBXL4 and Down syndrome: In addition, some monogenic diseases, CNV syndromes, and intrauterine infection-related diseases involve concurrent cataract and heart defects, such as oculo-facio-cardio-dental syndrome (OFCD) caused by BCOR mutations [10], FBXL4-related encephalomyopathic mitochondrial DNA depletion syndrome by FBXL4 mutations [11], Sengers syndrome caused by AGK mutations [12], Nance-Horan syndrome caused by NHS mutations [13], Down’s syndrome caused by trisomy 21 [14], and congenital rubella syndrome caused by rubella virus intrauterine infection [15].