Description:PMM2-CDG is a rare inborn error of metabolism caused by deficiency of the PMM enzyme, which leads to impaired protein glycosylation. While the disorder has primarily neurological presentation, there is limited knowledge about the specific brain-related changes that result from PMM deficiency. Utilizing 3D brain organoids derived from individuals with PMM2-CDG, we identified abnormal glucose metabolism in PMM2-CDG organoids, indicating disturbances in metabolic utilization.