PMON20 Snyder Robinson Syndrome: A Rare Syndrome
Authors: Manas F N U , Mols-Kowalczewski Barbara 
Published: November 2022

Abstract

Introduction
Snyder Robinson Syndrome (SRS) is a rare X-linked intellectual disability disorder caused by inactivating mutation in the spermine synthase (SMS) gene which is involved in polyamine biosynthesis. It was first described by Snyder and Robinson in 1969 and so far about 20 cases have been reported worldwide. The affected males have short stature, slender build with asthenic habitus, hypotonia, facial dysmorphism with a prominent lower lip, kyphoscoliosis, broad-based gait, osteoporosis with frequent fractures, developmental delay, seizures, and speech and motor disability. Hypotonia presents during the neonatal period and the developmental delay and facial dysmorphism are manifested within the first year of life. Osteoporosis develops within the first decade of life resulting in fractures in the absence of trauma or after minor trauma. No formal diagnostic criteria have been established for Snyder Robinson syndrome. The diagnosis is made based on clinical presentation and biochemical testing of spermine synthase enzyme activity. It is confirmed by molecular genetic testing by identification of a hemizygous loss-of-function SMS pathogenic variant. Currently there is no treatment guideline for Snyder Robinson syndrome. Speech, physical, and occupational therapy can be helpful for intellectual and developmental disability. Kyphoscoliosis is treatment per standard management by orthopedics and surgery is recommended for cleft lip. Calcium supplementations are used for osteoporosis to prevent recurrent fractures. The role of bisphosphonates for osteoporosis is controversial with no proven benefit or effectiveness in Snyder Robinson syndrome. Anti-seizure medications are recommended for seizures along with Neurology follow-up, though some affected individuals may have drug-resistant seizures.

Case Presentation
A 32-year-old male presented to the Endocrinology clinic as a new patient with his mother. He was referred by his primary care physician for monitoring of calcium. He had a past medical history of Snyder Robinson Syndrome. He had genetic testing in the past which showed mutation in the spermine synthase (SMS) gene. He was a thin man with a BMI around 19 kg/m2. He had intellectual disability, facial dysmorphism, kyphoscoliosis, abnormal gait, speech and motor disability. He had a history of seizures, but was currently not on any anti-seizure medications. He had a history of low bone density for age and history of fractures. He was taking calcium and multivitamin supplementation. He was seen by the physical medicine and rehabilitation department for physical and occupational therapy.

Conclusion
Although rare, Snyder Robinson syndrome should be suspected in males with intellectual disability, hypotonia, asthenic habitus with the diminished body bulk, bone abnormalities, facial dysmorphism, motor and speech disability, and seizures. The number of patients would increase in the future with the increasing use of genetic testing in patients who present with undefined developmental abnormalities.
Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.