Clinical features
Snyder Robinson syndrome is a rare condition characterized by global developmental delay/intellectual disability, low muscular tone, diminished muscle mass, seizures, nasal speech, osteoporosis with recurrent fractures, and progressive kyphoscoliosis. It affects only males.
Prevalence
Snyder-Robinson syndrome is a very rare condition. To date, nearly 60 patients have been identified, and it is impossible to estimate how many people have this syndrome. However, it is expected that more patients will be identified thanks to the newer genetic technologies currently available.
Inheritance
Snyder-Robinson syndrome is caused by mutations in the SMS gene. It is inherited in an X-linked recessive fashion: this means that affected males have a change in their only copy of the gene, whereas females with a mutation are usually not affected because they have a second copy of the gene that is normal.
Affected individuals result from a de novo mutation (i.e. the change happened in them for the first time and was not inherited) or, more commonly, have inherited the mutation from their mother, who is and healthy carrier. The risk for future pregnancies depends on the mother’s status. Prenatal testing is theoretically feasible once the mutation is known.