Liver phosphorylase deficiency, or glycogen storage disease type 6b (Hers' disease, GSD 6b) is a benign and rare form of glycogen storage disease. The disease usually occurs in childhood and is characterized by hepatomegaly and growth delay. Hypoglycemic episodes are mild or absent, and hypertransaminasemia and hyperlipidemia are moderate and unconstant. Hepatomegaly usually improves with age and disappears entirely at puberty. Transmission is autosomal recessive and mutations in the PYGL gene (14q21-q22) have been identified in patients. Diagnosis is based on biochemical findings revealing excess glycogen and partial deficiency of total and active phosphorylase in liver biopsy. A diet with high carbohydrate intake and regular meals prevents hypoglycemia in children, but most patients require no specific treatment. Prognosis is usually good.
Last update: September 2009