Glycogen debrancher deficiency is reproduced in muscle culture

Abstract
Muscle cultured from two adults with debrancher deficiency myopathy showed abnormal glycogen deposits by electron microscopy. Glycogen debranching activity was markedly decreased, but phosphorylase activity was normal. Lack of glycogen debraching acstivity in muscle cultures from debrancher‐deficient patients contrasts with the presence of a fetal isoenzyme of phosphorylase in muscle cultured from patients with McArdle disease and suggests that the genetic control of the debraching enzyme does not change during muscle development.