G1D - Glucose transporter type 1 deficiency syndrome

a. What happens once a diagnosis of G1D is made?

Once the diagnosis of G1D is confirmed, it is not uncommon for parents to feel both a sense of relief now knowing the actual cause for their child's symptoms as well as a sense of urgency to learn as much as possible about the treatment and management of the disorder. Because there is still so much more to learn about this rare disorder, treating and managing the condition is a life-long learning process for both families and their physicians. Families are therefore encouraged to develop strong collaborative relationships with their physicians. It is encouraging that the number of families and health care professionals interested in the disease is growing rapidly and significant advances and changes in the way we think about G1D may come in the near future.

b. How will my child develop?

Although developmental and cognitive delays are common in individuals with G1D, the degree of intellectual and developmental disability can vary greatly from person to person. This has been shown even among multiple affected members of the same family with the same gene mutation. This is most likely due to other genes as well as environmental factors not yet known that can influence and modify the symptoms of G1D. Early childhood intervention programs and targeted therapies can be effective in helping affected individuals reach their full developmental potential. It is encouraging that most individuals with G1D tend to have strong social and interpersonal skills enabling them to better interact with their peers and within their communities. In the case of G1D patients with seizures, and although the data are preliminary, there appears to be a correlation between the age of initiation of therapy to control seizures (ketogenic diet) and overall prognosis.

c. Are G1D patients prone to other diseases?

No other disease associations are known at this time.

d. Are there side effects from the ketogenic diet?

Common but easily treatable side effects of the diet include constipation, poor weight gain, and possible kidney stones. It is important to talk to your doctor about how to reduce these possible side effects. Also, because the diet does not provide all the necessary vitamins and minerals of a well balanced diet, a vitamin supplement may be indicated.

e. Does the ketogenic diet need to be maintained for life?

For unknown reasons, some patients with G1D have been able to successfully discontinue the diet at the onset of puberty. Others have remained on the diet and others resume treatment with seizure and other medications to reduce their symptoms.

f. Could G1D have been prevented?

Since most cases of G1D are a result of a new spontaneous mutation that occurs at the time of conception and nothing a parent did or did not do caused this to happen, there is no way to know if a child is at risk of having the disorder. Unless a disease causing mutation has been previously identified in a family at risk to have a child with G1D, there is no prenatal test to determine if a child will be born with G1D. Prenatal ultrasounds and current mandatory newborn screening tests do not detect G1D. If a disease causing mutation is known, prenatal diagnosis (amniocentesis or chorionic villus sampling) and possible preimplantation genetic diagnosis (the combination of in vitro fertilization and genetic testing to identify unaffected embryos) would be available.

g. Will there ever be a cure for G1D?

More research is needed. At the moment, there is no evidence that the brain will allow the introduction of normal DNA or cells capable of replacing the abnormal brain cells affected by G1D. New developments and advances in gene therapy are expected in the future.