glycogen storage disease VI (MONDO_0009294) is liver phosphorylase deficiency, or glycogen storage disease type 6b (Hers' disease, GSD 6b) is a benign and rare form of glycogen storage disease. Also known as: GSD due to liver glycogen phosphorylase deficiency, GSD type 6, GSD type VI, Glycogen Storage Disease Type VI, PYGL glycogen storage disease, glycogen storage disease caused by mutation in PYGL, glycogen storage disease type 6, glycogen storage disease type VI.