Glycogen-storage disease type 1b is a rare metabolic disorder, which affects the glucose-6-phosphatase metabolism. The liver, spleen and other tissues accumulate glycogen. Patients present with an enlarged liver and spleen, failure to thrive, kidney problems, hypoglycaemia (low blood sugar) and recurrent infections. The presence of an enlarged spleen can be associated with low red blood cells causing anaemia and thrombocytopenia whereas neutropenia is always present. Chronic neutropenia in these patients is accompanied by a defective function of the cells that are responsible for the killing of bacteria. Patients respond to treatment with G-CSF not only with an increase in ANC but also with improvement of the activity of their neutrophils.