Glycogen storage disease type VI (GSD VI), also known as Hers disease, is a type of hepatic glycogenosis characterized by mild clinical manifestations and a benign course. Individuals with GSD VI typically exhibit hepatomegaly, growth retardation, and variable but mild episodes of fasting hypoglycemia and hyperketosis during early childhood.
Hyperlacticacidemia and hyperuricemia are characteristically absent.
In addition, affected individuals may demonstrate elevated levels of serum transaminases, hyperlipidemia, hypotonia, and muscle weakness. These clinical features and biochemical abnormalities generally resolve by puberty. Rare variants of GSD VI may manifest as proximal renal tubule acidosis, myopathy, peripheral neuropathy, or fatal cardiomyopathy. GSD VI is caused by a deficiency in the hepatic glycogen phosphorylase enzyme.