Symptoms are usually mild, and myopathy may be asymptomatic. A neonatal form with generalized muscular hypotonia and respiratory insufficiency has also been described. [rarediseases.info.nih.gov]

CONCLUSION: Our findings demonstrate that muscle PHK deficiency may present as an almost asymptomatic condition, despite a mild impairment of muscle glycogenolysis, raised CK levels, and glycogen accumulation in muscle. [ncbi.nlm.nih.gov]

The symptoms of disease in the liver group are similar, ranging from symptomatic hypoglycemia and ketoacidosis to largely asymptomatic enlargement of the liver (hepatomegaly). [britannica.com]

The discovery of oligosymptomatic and asymptomatic sibs suggested that there are persons with undiagnosed hepatic glycogen synthase deficiency. [sandwalk.blogspot.com]

Clinical Onset age: Childhood Cardiomyopathy (30%): Dilated; Tachycardia Myopathy (50%) Weakness: Some patients Fatigue & Exercise intolerance Rhabdomyolysis (20%) Bifid uvula (85%) Skeletal: Pierre Robin sequence, Cleft palate, Short stature Cerebral thrombosis [neuromuscular.wustl.edu]

Clinical features are muscle hypotonia and cirrhosis. Death from liver disease usually occurs before age 2. [icd10data.com]

hypotonia, hypercholesterolemia Treatment: Nonspecific Type VIII/IXa: X-linked phosphorylase kinase PHKA2 (Xp22)* Type IXb Liver and muscle phosphorylase kinase PHKB (16q12-q13)* Type IXc Liver phosphorylase kinase PHKG2 (16p12.1-p11.2)* Type IXd Muscle [msdmanuals.com]

Thus, not only does the increased intracellular calcium increase the rate of muscle contraction it increases glycogenolysis which provides the muscle cell with the glucose it needs to oxidize to satisfy the increased ATP it needs for contraction. [themedicalbiochemistrypage.org]