Mounting evidence indicates that mutations in core components of the major and minor spliceosomes are responsible for spliceosomopathies representing a group of syndromes, including Nager syndrome (OMIM#154400) and thrombocytopenia-absent radius syndrome (OMIM#154400), which are caused by mutations of SF3B4 and RBM8A, respectively. This evidence concerns the gene SF3B4 and Nager acrofacial dysostosis.