WHAT IS GLUCOSE TRANSPORTER DEFICIENCY SYNDROME (Glut1 DS)?

Glucose transporter deficiency syndrome (Glut1 DS) is a pediatric brain energy metabolic syndrome. Glut1 DS was first discovered in 1991 by Dr. Darryl DeVivo at the Colleen Giblin Laboratories, Columbia Presbyterian Medical Center. We know of hundreds of children who have Glut1 DS but believe there may be thousands of children who are undiagnosed. Having Glut1 DS means that an afflicted child's cells do not pick up and transport glucose to the brain properly. Glucose is the principal source of fuel to the brain. Children with this disorder have a myriad of physical and mental disabilities, ranging from mild to so severe that they cannot walk or talk.

Glut1 DS Symptoms
They are many, and they vary in degree. Most often, a child or infant presents with unexplainable seizures. The doctors rule out the usual causes and cannot determine why the child's seizures persist. Those affected with Glut1 DS usually do not respond to anti-seizure medications. In fact, the gold standard for pediatric seizures, phenylbarbitol, actually inhibits glucose transport to the brain. So, babies and children who are put on this medication usually get even worse symptomatically.

In addition to seizures, other symptoms of Glut1 DS include low muscle tone which leads to physical difficulties including problems with crawling, jumping, walking, running, riding a bike, kicking a ball and many other typical childhood physical activities. All children with Glut1 DS experience problems with speech, both receptive and expressive. This means they may not be able to speak at all, or that they have slurred speech or difficulty accessing and articulating sounds and words and sentences. They also have cognitive and learning delays and disabilities. And if their brains do not get the energy needed for brain growth, microcephaly (shrunken heads) occurs. For a more thorough and scientific discussion of Glut1 DS go to the Colleen Giblin Laboratories website, www.giblinlabs.org and read Dr. DeVivo's paper on Glut1 DS.

Treatment for Glut1 DS
The only known treatment to date is a very restrictive diet called the ketogenic diet which is usually used for children with seizure disorders that do not benefit from conventional drugs. It is a treatment of last resort for them. For children with Glut1 DS, it is the only treatment that may help control the seizures and hopefully help with providing energy to the brain. However, it is currently unknown how effective this treatment may be.

The ketogenic diet

The ketogenic diet is a very restrictive, calorie-limited, high fat diet. All food consumed is based on a ratio of fat to protein and carbohydrate combined, usually a 4:1 or 3:1 ratio, (3 or 4 grams of fat to 1 gram of protein and carbohydrate combined). No sugar is allowed and minimal carbohydrate is included. Each meal or snack is measured in grams and typically includes a small amount of protein, a tiny amount of a lower carbohydrate fruit or vegetable and a large amount of oil, butter, mayonnaise or heavy cream as the fat source. This diet is so precise and restrictive that children on it must avoid even topical ingredients that may have sugar sources or carbohydrate (examples are medications, toothpaste, lotions, sunscreen). 

Strict compliance with this diet causes the body to produce ketones. Ketones are used by the brain as an alternate fuel source.  The ketogenic diet usually helps with seizure control.  But, it is currently unknown how much this diet may benefit the other symptoms of Glut1 DS deficiency syndrome.  Every child on this diet must be monitored to measure for adequate ketones. The best way to measure ketones is with a blood monitoring machine that requires pricking the child's finger. If ketones are too low, the child may have seizures or other symptoms of Glut1 DS deficiency syndrome, and if ketones are too high, acidosis or other side effects can occur. 

The ketogenic diet does not provide adequate nutrition.  Children on the diet take various daily supplements to try to keep their bodies properly nourished and growing. Their blood, bodies and organs are carefully monitored by doctors to watch for and try to prevent potential problems caused by the diet. Some side effects that can occur while on this diet include kidney stones, high cholesterol, dehydration, slow growth or weight gain and bone fractures. The long term effects of the ketogenic diet on the body are not known. But, we do know that it helps children with Glut1 DS deficiency syndrome while they wait for a cure.

Glut1 DS will not go away without a cure
People often ask whether a child with Glut1 DS will outgrow it. The answer is no. It is genetic, and children with Glut1 DS will never outgrow it. The only option is a cure.

The Miracle is Possible
Dr. DeVivo and his team of researchers at Columbia Presbyterian are working toward finding a cure for Glut1 DS. Their efforts will lead to the miracle of children with Glut1 DS living lives free of neurological and physical symptoms and disabilities. But, it is a race against time. As these kids develop, their brains are developing without the necessary amount of energy to do so. Clearly the sooner there is a cure, the better the odds are for all children with Glut1 DS.

Next: Finding the cure for Glut1 DS