Glucose Transporter Type 1 Deficiency Syndrome (GLUT1-DS) is caused by the SLC2A1 gene mutation, which encodes the glucose transporter proteins to the brain Neurological manifestations occur in three main domains: seizures, abnormal movements, and cognitive disorders. The diagnosis is presumed upon the finding of low CSF glucose and confirmed by the gene molecular analysis. Accurate diagnosis is important because it has a specific treatment, which is ketogenic diet. Objective: To analyze two SD-GLUT1 pediatric patients with unusual phenotype. Clinical Case: We present the case of two siblings who presented absence seizures and a paroxysmal movement disorder. Both patients were studied, finding low CSF glucose. The diagnosis of GLUT1-DS was confirmed with molecular analysis. Specific treatment with ketogenic diet achieved good response in both cases. Conclusions: We present their peculiar clinical characteristics that allowed us to suspect this wide phenotypic spectrum. Correct and timely diagnosis and treatment can significantly improve the quality of life of those affected.