Glycogen Storage Disorders Type I in Vietnam: Genotype, Phenotype, and Outcome

Background: Glycogen storage disorder (GSD) is a rare inborn error of the synthesis degradation of glycogen metabolism. Glycogen storage disorder type I (GSD I) is the common type of GSD and includes two types: Ia and Ib. There is currently no study on this disease in Vietnam.

Methods: This is a case series that analyses the phenotype, genotype, and outcome of 18 patients with GSD type I at the Vietnam National Children`s Hospital from 2000 to 2022.

Results: There were 12 patients with GSD Ia and 6 with GSD Ib. The gender ratio was 1:1 and the mean age of onset was 5−6 months (ranging from 7 days to 12 months). Abdominal distension accounted for 87.5% and 100%, and hepatomegaly accounted for 60% and 100% in GSD Ia and GSD Ib, respectively. All patients had elevated transaminase and hyperlactatemia ranging from 3.8 – 22 mmol/l. Hypoglycemia (0.1−2.6 mmol/l) was present in 37.5% and 50% of patients with hypertriglyceridemia (3.5−15.5mmol/l) in 85.7% and 100% of GSD Ia and GSD Ib patients, respectively. Metabolic acidosis and hypercholesterolemia were more common in GSD Ia than Ib. Five mutations of the G6PC gene were identified: c.356AT (41%), c.518TC (31.8%), c.648GT (13.6%), c.248GA (9.1%), c.809GT (4.5%). There were three mutations c.706_708del (75%), c.446GA (16.7%), and a novel stop-gain mutation c.1259AG (8.3%) in the SLC37A4 gene. After diet therapy, 17/18 follow-up cases lived with the current mean age of 9.6 (2−23 years old) and physical development delays. However, a patient with GSD Ia died at 9 years old from cirrhosis. Conclusions: GSD Ia is the more common type than GSD Ib in Vietnam and there are remarkable differences in their phenotype. There are two common mutations of the G6PC gene in Vietnam: 356AT, c.518TC.

Keywords: GSD Ia, GSD Ib, G6PCgene, SLC37A4 gene