International GLUT1 Awareness Day Date in the current year: July 10, 2025

GLUT1 (glucose transporter 1) is a transport protein that facilitates the transport of glucose across cell membranes, including those of the blood-brain barrier. It is encoded by the SLC2A1 gene. Mutations in this gene can cause several genetic disorders, including GLUT1 deficiency syndrome, idiopathic generalized epilepsy 12, dystonia 9, and stomatin-deficient cryohydrocytosis.

Patients with GLUT1 deficiency syndrome have mutations in the SLC2A1 gene that result in the production of an insufficient amount of GLUT1 protein. Consequently, brain cells do not receive adequate glucose, impacting brain development and function. While GLUT1 deficiency can be inherited, approximately 90% of cases result from spontaneous (de novo) mutations.

GLUT1 deficiency syndrome causes a wide range of symptoms, including infantile-onset seizures, developmental delay, coordination problems, muscle stiffness, acquired microcephaly (smaller-than-normal head), and cognitive impairment. The most commonly reported initial signs of GLUT1 deficiency are unusual eye or head movements, seizures, missing developmental milestones, unusual body movements, and muscle tone issues.

Depending on the clinical presentation, there are two types of GLUT1 deficiency. Type 1, or classic GLUT1 deficiency, typically begins in infancy with seizures, developmental delay, movement disorders, and often microcephaly. It is characterized by low glucose in the cerebrospinal fluid. Type 1 tends to be more severe and recognizable early on.

Type 2 GLUT1 deficiency, also known as non-classic or atypical GLUT1 deficiency, includes a broader range of symptoms that are often milder. These symptoms may begin later in life and include episodic movement issues or subtle cognitive problems. People with type 2 GLUT1 deficiency may not experience the hallmark seizures or may have only borderline low CSF glucose.

Seizures caused by GLUT1 deficiency typically do not respond to anticonvulsant medications because the medications do not address the underlying cause: a lack of glucose in the brain. The standard treatment for the disorder is a ketogenic diet that is low in carbohydrates, moderate in protein, and high in fat. This diet causes the body to use fats rather than carbohydrates, such as glucose, as a source of energy. The diet must be carefully tailored to each patient’s individual needs.

However, the ketogenic diet is not a cure. Patients with GLUT1 deficiency must adhere to it for life under medical supervision. It is crucial to diagnose GLUT1 deficiency early and start patients on the ketogenic diet promptly to prevent severe developmental delay and cognitive impairment.

International GLUT1 Awareness Day was established by the GLUT1 Deficiency Foundation (G1DF), a patient advocacy organization led by parents that provides support for patients with GLUT1 deficiency and their families through awareness, advocacy, education, and research. This awareness day’s main goals are to educate affected families, health professionals, and the general public about GLUT1 deficiency; advocate for patients and their families; and provide support and funding for research into new treatments and, ideally, a cure.