Deficiency of spermine synthase causes excessive spermidine accumulation and a lack of spermine.141 Patients with Snyder-Robinson syndrome, a syndrome caused by loss-of-function mutations of the spermine synthase gene, exhibit severe OP and kyphoscoliosis and have BMSCs with impaired capacities for osteogenic differentiation and mineralization.142. Here, SMS is linked to X-linked intellectual disability, Snyder type.