[Ketogenic diet reintroduction in an adult patient with glucose transporter type 1 deficiency syndrome].

Glucose transporter type 1 deficiency syndrome is a metabolic encephalopathy caused by impaired glucose transport across the blood-brain barrier, and ketogenic diet therapy is the first-line treatment. The patient was a 21-year-old woman. In childhood, she developed postexercise hemiparesis and decreased activity during the fasting period. Cerebrospinal fluid testing revealed low glucose levels. Subsequent genetic testing identified a pathogenic SLC2A1 variant, leading to the diagnosis. Her symptoms improved with ketogenic diet therapy. After discontinuation at 18 years of age, she remained stable. However, fasting-related fatigue recurred at the age of 20 years. At 21 years of age, she developed brief (~20 s) episodes of impaired awareness with decreased muscle tone. The EEG showed 3-4 Hz generalized spike-and-wave complex. Ketogenic diet therapy was reintroduced with a ketogenic ratio of 1.5:1, leading to reduced EEG abnormalities and symptomatic improvement. Although symptoms usually lessen in adulthood, the reintroduction of ketogenic diet therapy should be considered when symptoms relapse after adolescence.