In fact, although to date very heterogeneous patients from a genetic point of view (carriers of STAG1 deletions, frameshift variants, missense) have been identified, and there does not seem to be a mutational hot spot for the STAG1 gene which has instead emerged for other clinical conditions such as Schinzel-Giedion syndrome (SGS, OMIM 269150) [18], all the patients described share specific clinical features. This evidence concerns the gene STAG1 and Schinzel-Giedion syndrome.