Our team is working on a study to better understand neurological problems, including seizures and developmental delays, that occur in many individuals with HI/HA syndrome. The study involves a one day visit to The Children's Hospital of Philadelphia and The University of Pennsylvania for a specialized magnetic resonance imaging scan (MRI) of the brain, an electroencephalogram (EEG), blood draw, and completion of questionnaires to evaluate development and behavior. The entire study visit is expected to take about four hours. If you are interested in learning more, please contact us at HIResearch@email.chop.edu.

You or your child are being asked to take part in this research study because you have Glycogen Storage Disease Type III (GSD III). The purpose of this research study is to better understand blood sugar variability, muscle strength and function, and impact of Glycogen Storage Disease Type III (GSD III) on overall health. You will not receive any treatment for your GSD III as part of this study, but the information you provide will be helpful for the study sponsor, Ultragenyx Pharmaceutical Inc., to develop a new therapy for GSD III.

If you agree to take part, your participation will last for about 26 weeks and will involve up to 2 study visits to the hospital along with up to 26 phone calls. There will be no changes to your treatment regimen for GSD III as part of this study.

As a participant in the research you will:

• come to the hospital for 1-2 in person visits to complete interviews and questionnaires,
• wear a blinded continuous glucose monitor (CGM) 3 months and an unblinded CGM for 3 months,
• complete fingerstick blood sugar checks, maintain a nutrition diary for 3 or more weeks throughout the study,
• maintain a hypoglycemia symptom diary, and
• upload CGM and HHG device data to a study-provided laptop weekly.

The main risks of this study are from hypoglycemia related to your diagnosis of GSD III and a loss of confidentiality. There are no direct benefits to you for participating in this study but the information collected as part of this study will help researchers better understand GSD III.

Our team is working on a study to see if children with HI/HA Syndrome tolerate Vitamin E supplementation. This is an experimental, non-FDA approved use of Vitamin E which will lead to further studies to evaluate if Vitamin E can be used as a treatment for HI/HA. The study involves taking Vitamin E once a day for two weeks at home, completing a tolerability questionnaires, and two, one-day visits to the CHOP outpatient Center for Human Phenomic Science (one visit before and one visit after taking the Vitamin E supplement for two weeks). During each study visit, fasting oral protein tolerance will be performed and blood samples will be drawn.