A 9-month-old infant has a 6-month history of progressive muscle weakness and congestive heart failure with a markedly enlarged heart. She can no longer roll over, is flaccid, and her head flops back when she is lifted. She remains alert and interested in her environment. A muscle biopsy shows increased glycogen particles in lysosomes. The most likely cause of these symptoms is a deficiency of which of the following enzymes?

Question

Quizplus · Accepted Answer

The symptoms and biopsy findings are indicative of Pompe disease, which is caused by a deficiency of the enzyme acid maltase (also known as lysosomal α-glucosidase). Glycogen storage disease type II (GSDII) is also known as Pompe disease and results from defects in the gene encoding lysosomal acid maltase. Thus, the disease is also referred to as acid maltase deficiency (AMD). The clinical presentation of GSDII encompasses a wide range of phenotypes, but all include various degrees of cardiomegaly. Additional clinical manifestations associated with idiopathic cardiomegaly accompanied by storage of glycogen are indicative of Pompe disease. These symptoms included hepatomegaly, marked hypotonia, muscular weakness, and death before 1 year of age. The different phenotypes can be classified dependent upon age of onset, extent of organ involvement, and the rate of progression to death.

A 9-Month-Old Infant Has a 6-Month History of Progressive Muscle