Expanding the phenotype of GNAO1 related movement disorders: Two cases with mild phenotypes.

Background: Pathogenic variants in the GNAO1 gene have been previously linked to severe epileptic encephalopathy, severe progressive movement disorders, developmental delay, and intellectual disability. Method: report of 2 cases. Results: we present 2 unrelated girls, an 18-year-old, and a 4.5-year-old, with mild phenotypes. While each was noted early on to have hypotonia, failure to thrive, and developmental delay, they both have made significant progress with various therapeutic interventions. Neither have had any developmental regression, seizures or choreoathetosis. Conclusion: these 2 cases further expand the phenotype spectrum of GNAO1 mutations, which is important for counseling and to help guide management plans.