A novel mutation in spermine synthase (SMS) leads to a mild case of learning disabilities in a patient with Snyder-Robinson syndrome
Snyder-Robinson syndrome (SRS) is a rare X-linked recessive disorder characterized by moderate to severe intellectual disability, asthenic build, facial dysmorphism, skeletal abnormalities, developmental delay, and seizures. This disorder is caused by a mutation in the spermine synthase (SMS) gene, which helps convert spermidine to spermine. Currently, there are about 20 reported cases of SRS in the literature. At the Center for Rare Childhood Disorders, whole genome sequencing identified a mutation in the SMS gene at c.746 A>G, p.Y249C in a male patient with kyphosis, tonic-clonic seizures, and osteoporosis. However, his case is unique in that he presents with a mild learning disability. To confirm the diagnosis of SRS, spermidine (SPD) and spermine (SPM) protein levels were compared to other affected individuals. This case demonstrates a milder presentation of SRS and expands the phenotype beyond the reported literature. This information can be used to help diagnose similar cases in the future.