A case report of the late-onset Cori-Forbes disease in a white European adult

Cory-Forbes disease, also known as glycogen storage disease type III (GSD III), is a rare genetic disorder characterized by impaired glycogen metabolism and manifested by varying degrees of damage to the liver, heart, and skeletal muscles. GSD IIIa is the most common subtype, occurring in approximately 85 % of patients and characterized by both liver and muscle involvement. GSD IIIb, which affects only the liver, occurs in about 15 % of cases. Types IIIc and IIId also exist but are considered fairly rare conditions and these patients are clinically indistinguishable from those with GSD IIIa. In neonates and young children, liver damage manifests as hepatomegaly and growth retardation, as well as fasting ketotic hypoglycemia, hyperlipidemia, and elevated liver enzymes. In adolescence and adulthood, these symptoms become less pronounced. Many people have heart lesions accompanied by cardiac hypertrophy or cardiomyopathy. Myopathy, which leads to muscle weakness, can be noticeable as early as childhood and progresses slowly, becoming more apparent in the third or fourth decade of life. The prognosis is generally favorable but can vary greatly from person to person. Treatment consists of diet, avoidance of fasting, hypoglycemia, and myoglobinuric attacks, which are very rare in these patients. Long-term sequelae, such as muscle and heart damage, liver fibrosis or cirrhosis, and hepatocellular carcinoma, can significantly affect prognosis and quality of life. Understanding the clinical picture of this disease can contribute to early diagnosis, which will improve the quality of life of patients, and timely therapy is key to preventing complications and improving prognosis. However, there are limited publications on the late onset of clinical symptoms of GSD III.