Objective: To present a case of GLUT1 deficiency syndrome diagnosed in adulthood emphasizing the need to keep this diagnosis in differential for adult patients with seizures and movement disorders. 

Background: GLUT1 deficiency syndrome (GLUT1-DS) is a rare metabolic disorder caused by mutations in the SLC2A1 gene, impairing glucose transport across the blood-brain barrier. Early recognition and initiation of a ketogenic diet are critical for symptom control. However, delayed diagnoses can lead to prolonged ineffective treatment, worsening neurological dysfunction

Method:

A 37-year-old female with a longstanding epilepsy diagnosis presented with progressive dystonia and worsening motor symptoms. Her history included seizure-like episodes from infancy, delayed developmental milestones, and poor response to antiepileptic drugs (AEDs). Over time, she developed dystonic posturing, limb stiffness, and episodic loss of motor control. Multiple EEGs remained inconclusive, and a movement disorder diagnosis led to treatment with carbidopa-levodopa and other medications, yielding only partial relief. Genetic testing for SLC2A1 confirmed GLUT1-DS. A ketogenic diet, providing 70–80% of calories from fat, resulted in significant motor improvement and reduced episode frequency.

Results: This case underscores the diagnostic challenges of GLUT1-DS, particularly in adults with epilepsy and movement disorders. Misdiagnosis delays appropriate treatment, prolonging disability. While GLUT1-DS is typically recognized in infancy, this case highlights the need to consider it in patients with refractory epilepsy, dystonia, or atypical movement disorders. Importantly, dietary intervention remains beneficial even when initiated in adulthood, improving quality of life and neurological function.

Conclusion: Early genetic testing for GLUT1-DS should be considered in patients with unexplained epilepsy and movement disorders to optimize management with a ketogenic diet, regardless of age at diagnosis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnosis-of-glut1-deficiency-syndrome-in-adulthood/