Glycogen storage diseases (GSDs) or glycogenoses comprise several rare inherited diseases caused by abnormalities of the enzymes that regulate the synthesis or degradation of glycogen. We report on a male patient with type Ia GSD (GSD Ia) who was followed-up for more than 20 years. He had been diagnosed with GSD Ia based on biochemical tests and the glucose-6-phosphatase (G6Pase) enzyme assay from a liver biopsy at 6 years old, due to problems of hepatomegaly, growth retardation, and recurrent hypoglycemic episodes. The introduction of uncooked cornstarch improved his quality of life only in the first 8-year follow-up period. At 17 years old, gouty arthritis with multiple tophi and generalized xanthomatosis developed. Later, hepatocellular adenoma, nephrolithiasis, and gastrointestinal bleeding occurred at the age of 20, 23, and 24 years, respectively. At 26 years old, he suffered from acute renal failure and polyradiculoplexopathy. The problem of delayed puberty persisted. The story of this patient illustrates the multisystemic nature of GSD Ia and highlights the need for careful dietary therapy and long-term follow-up.