Glycogen storage disease type III (GSD III) is characterized by the variable liver, cardiac muscle, and skeletal muscle involvement. GSD IIIa is the most common subtype, present in about 85% of affected individuals; it manifests with liver and muscle involvement. GSD IIIb, with liver involvement only, comprises about 15% of all affected individuals.
Hepatomegaly is due to the accumulation of branched-chain polysaccharides (limit dextrins) and ketosis is because of the ineffective breakdown of glycogen leading to the burning of stored fat in the body where ketone bodies are produced as a byproduct. Thank you.