Andersen disease is due to deficiency of which enzyme?

• A. Glycogen branching enzyme
• B. Glycogen phosphorylase
• C. Glycogen debranching enzyme
• D. Glucose-6-phosphatase

Answer: (A)

Andersen disease, also known as glycogen storage disease type IV, results from a deficiency of the branching enzyme that normally creates alpha-1,6 branches in glycogen. Without this enzyme, glycogen becomes predominantly linear with few branches, forming amylopectin-like structures that are poorly soluble and tend to accumulate in liver, heart, and muscle. This leads to hepatosplenomegaly and progressive organ dysfunction. Other enzymes listed correspond to different glycogen storage diseases (for example, deficiency of glycogen phosphorylase causes Hers disease; debranching enzyme deficiency causes Cori disease; glucose-6-phosphatase deficiency causes Von Gierke disease), but Andersen disease is specifically due to the branching enzyme deficiency.