Glycogen storage disease type Ib (GSD Ib) is an inherited disorder caused by the deficiency of an enzyme called glucose-6-phosphate translocase which acts as a transporter for the substrate of G6Pase. With defective enzyme function, individuals with GSD type Ib cannot maintain blood glucose levels during fasting and will develop low blood sugar. Symptoms become obvious as early as three to four months after birth and affected infants commonly present with low blood sugar, seizures, high lactic acid level, high uric acid and lipid levels in blood and enlarged liver. As they grow older, poor height and weight growth is noted. Kidney disease, high blood pressure in the lungs and decreased bone density are complications that can also occur as individuals grow older. With proper dietary management and careful medical surveillance, GSD Ib patients can live a normal lifespan. GSD Ib is caused by mutations in the SLC37A4 gene.