[P3-88] Treatment of a case with GNAO1 associated movement disorder and cerebral folate deficiency: role of folinic acid?
We describe a Chinese boy with guanine nucleotide-binding protein (G-protein), alpha activating activity polypeptide O (GNAO1) gene mutation and coexisting cerebral folate deficiency (CFD). He is a 9-year-old boy presented with hypotonia, intellectual disability and significant motor delay. He has infrequent seizures since 2 years old and transient chorea movements during febrile illnesses at 5 years old. He developed refractory chorea movements triggered by an influenza B upper respiratory infection at age of 8. Extensive investigations including MRI brain, autoimmune encephalitis antibodies, infection and metabolic screen were unremarkable except a low 5-methyltetrahydrofolate (5-MTHF) level in cerebrospinal fluid (CSF) with normal blood folate status. His involuntary movements showed no significant clinical response to intravenous immunoglobulin, steroid, tetrabenazine, carbamazepine and clobazam in addition to sodium valproate. However, he had gradual improvement one week after starting folinic acid treatment and nearly completely subsided one month later. He has no further prolonged chorea movements and is currently taking folinic acid at 3.5mg/kg/day together with low dose carbamazepine and clobazam for seizure control. He was later confirmed to have GNAO1(c.736G>A) mutation by whole-exome sequencing. Our patient has clinical phenotype of GNAO1mutation with predominant movement disorder and few seizures. More studies are needed to investigate the association between GNAO1 mutation and CFD which share similar clinical features. We propose that screening for CSF 5-MTHF level should be considered in patients with GNAO1 associated movement disorders. Further case studies treated by folinic acid may help to clarify its role as a possible treatment.