[Genetic and clinical characteristics of 26 cases with glycogen storage disease type Ⅲ]

Objective: To investigate the genetic, clinical, and post-treatment characteristics of patients with glycogen storage disease type Ⅲ (GSD Ⅲ). Methods: A retrospective cohort analysis was performed on the genetic and clinical data of 26 cases with GSD Ⅲ who visited the Children's Hospital affiliated with Fudan University from June 2017 to December 2023. The patients were divided into non-missense variation and missense variation groups according to the types of mutation in the AGL gene.The correlation between genotype and phenotype was analyzed. All patients were treated with uncooked cornstarch after diagnosis. The changes before and after treatment were compared in patients who underwent more than twelve months of follow-up. A P value of <0.05 was used to denote statistical significance. Results: Among the 26 cases enrolled, 13 were female and 13 were male, and the median age of diagnosis was 28 (6 to 134) months. A total of thirty-five different types of AGL gene variation were detected, with c.1735+1G＞T (9/52, 17.3%) as the hotspot variation. The common clinical manifestations were elevated aminotransferases (26/26, 100%), hepatomegaly (25/26, 96.2%), fasting hypoglycemia (25/26, 96.2%), hyperketonemia (16/18, 88.9%), hypertriglyceridemia (TG) (20/26, 76.9%), elevated CK (16/25, 64.0%), and an abnormal electrocardiogram (12/16, 75.0%). Four cases (15.4%) had symptoms of myopathy at diagnosis. Liver biopsy was performed in eighteen cases, among whom 83.3% (15/18) had liver fibrosis≥S2. The number of cases with elevated levels of CK (P＝0.031) and ALT (P＝0.038)was pronounced in the non-missense variation group compared to that in the missense variation group. There were no statistically significant differences in age, height, liver size, degree of fibrosis, fasting blood glucose (Glu) and TG (P>0.05). The median follow-up time of 14 cases was 40.5 (20-73) months, with improvement in body stature, reduced liver size, decreased ALT and TG, and improved Glu. However, four (28.6%) cases had new myopathy symptoms with raised CK (P<0.05) and with advancing age, increased ALT diminished while CK level elevated (P<0.05). Conclusions: The common clinical manifestations at the early stage of the GSD Ⅲdiagnosis are elevated aminotransferases, hepatomegaly, fasting hypoglycemia, hyperketonemia, high triglycerides, elevated CK, and fibrotic liver in China. Myopathy symptoms may arise following uncooked cornstarch treatment; however, there is significant improvement in height, liver-related, and metabolic parameters.