Glycogenose

Glycogenose, more commonly referred to as glycogen storage disease (GSD), is an umbrella term for a group of inherited metabolic disorders caused by defects in enzymes involved in glycogen synthesis or glycogen breakdown. These defects disrupt the proper storage and mobilization of glycogen, leading to energy deficiency in liver, muscle, heart, and other tissues. The result is a spectrum of symptoms that can include hypoglycemia, hepatomegaly, muscle weakness, fatigue, and, in some forms, cardiomyopathy or growth problems.

GSDs are typically classified by the deficient enzyme and the primary tissue affected. Hepatic forms primarily involve the liver, while muscular forms affect skeletal muscle and sometimes the heart. Many disorders are caused by autosomal recessive mutations, though several forms have X-linked inheritance or complex inheritance patterns. Notable examples include GSD I (von Gierke) due to glucose-6-phosphatase deficiency, GSD II (Pompe) due to acid alpha-glucosidase deficiency, GSD III (Cori) due to a debranching enzyme defect, GSD IV (Andersen) due to a branching enzyme defect, and GSD V (McArdle) due to muscle glycogen phosphorylase deficiency. Each type presents with a characteristic pattern of organ involvement and age of onset.

Diagnosis relies on clinical features supported by biochemical testing (such as fasting hypoglycemia, elevated lactate, uric acid or triglycerides) and genetic testing to identify the causative mutations. Enzyme assays and tissue biopsy can aid confirmation and clarify glycogen structure abnormalities. Management focuses on preventing metabolic crises and improving quality of life, including regular carbohydrate intake (frequent meals or uncooked cornstarch in hepatic forms), dietary adjustments, physical therapy for muscle forms, and, in some cases, enzyme replacement therapy (notably for Pompe disease). Prognosis varies widely by type and severity.