Truncating mutations in MAGEL2, which lead to a shortened protein, cause Schaaf-Yang syndrome (SYS). We have compiled all reported cases and provide Clinical Management Recommendations to help families and physicians manage these patients. We have further characterized the cellular effects of these mutations. We have introduced a normal (full) or truncated form of the gene in human cell lines and looked for the intracellular location of the protein. Truncated MAGEL2 is found more in the nucleus than full MAGEL2. In patients’ fibroblasts we have observed differences in the expression of certain genes, the levels of excreted amyloid beta 1-40 and the intracellular glutamine. These could be used as biomarkers when assessing potential treatments. (By Dr. Roser Urreizti, https://jmg.bmj.com/content/early/2022/09/06/jmg-2022-108690 )