We report here on a case of genetically confirmed type Ia glycogen storage disease (GSD) that was diagnosed in the military hospital. A twenty-year old soldier was admitted to the hospital with abdominal fullness. He had a past medical history of hepatomegaly that was firstly recognized at six months after birth, and he had been followed-up at an outpatient clinic with the presumptive diagnosis of type III GSD. He also had a history of growth hormone therapy because of growth retardation. However, he arbitrarily refused medical observation from 14 years of age. On the physical examination, the height of the patient was 163.1 cm and significant hepatomegaly was observed. Significantly abnormal liver-associated paramters were observed on the laboratory findings and multiple hepatic adenomas were observed on the CT exam and MRI scan. To determine the proper treatment, we tried to confirm the exact type of GSD in the patient. By mutational analysis, we found the c.648G>T homozygote splicing mutation in the G6PC gene and the patient was confirmed as having the type Ia GSD.