We report a case of an 18-month-old girl with glycogen storage disease type Ib (GSD Ib). Her neutrophil counts had gradually decreased to less than 500/µL by the age of 3 years. However, there were no recurrent bacterial infections. Mutation analysis of the glucose-6-phosphate translocase (G6PT) gene revealed a compound heterozygous missense mutation (Ala148Val/Gly273Asp).