SNP Shot: Genomic Insights

Glycogen storage disease type III (GSDIII), also known as Cori disease, is a genetic disorder characterized by the accumulation of glycogen, a complex sugar, within the body's cells. This abnormal buildup results in structurally flawed glycogen, impairing the proper function of various organs and tissues, especially the liver and muscles.

GSDIII is further classified into subtypes IIIa, IIIb, IIIc, and IIId, based on their specific signs and symptoms. Types IIIa and IIIc predominantly affect both the liver and muscles, while types IIIb and IIId primarily affect the liver. Differentiating between subtypes affecting the same tissues can be difficult. GSDIII types IIIa and IIIb are the most common forms of this disease.

Individuals with GSDIII, regardless of the subtype, may experience low blood sugar (hypoglycemia), elevated levels of fats in the blood (hyperlipidemia), and increased liver enzyme levels from infancy. As they grow older, children often develop an enlarged liver (hepatomegaly). While the liver typically returns to its normal size during adolescence, some individuals may develop chronic liver disease (cirrhosis) and eventual liver failure. Growth may be delayed in people with GSDIII due to liver problems, potentially leading to short stature. In rare cases, non-cancerous liver tumors known as adenomas may occur.

Individuals with GSDIIIa may develop muscle weakness (myopathy) later in life. These muscle problems can affect both the heart muscle (cardiac muscle) and the muscles responsible for movement (skeletal muscles). The severity of muscle involvement varies considerably. Early signs and symptoms often include poor muscle tone (hypotonia) and mild myopathy in early childhood. The myopathy can progress by early to mid-adulthood. While some individuals with GSDIIIa develop a weakened heart muscle (cardiomyopathy), heart failure is rare. Others with GSDIIIa may not experience any heart-related problems.

Inheritance:

GSDIII is inherited in an autosomal recessive pattern. This means that a person must inherit two copies of the mutated gene, one from each parent, to develop the condition. The parents, who each carry only one copy of the mutated gene, are typically unaffected and show no signs or symptoms of the disorder.