Review Question - QID 106621

This patient is suffering from deficiency of alpha-1,6-glucosidase, which is also known as glycogen debranching enzyme.

There are several types of glycogen storage disorders. These disorders all share the common feature of having abnormal glycogen metabolism. The disorders are numbered in order of the pathway from the end (glucose release) to the beginning (breakdown of glycogen polymer). The particular point of breakdown in the pathway leads to the particular presentation of each disease. The vignette describes a case of type III disease (Cori disease), which is due to an inability to debranch glycogen. (Mnemonic: Cori = Can't Catabolize branches.) Patients present with hepatomegaly and hypoglycemia. Biochemical analysis will shown abnormal short outer glycogen chains.

Figure A is a liver biopsy specimen from a patient with Cori's disease. The hepatocytes are distended with large stores of glycogen.

Incorrect Answers:
Answer 1: Type V (McArdle's) glycogen storage disease results from increased muscle glycogen that cannot break down, leading to painful cramps.
Answer 3: Type I (Von Gierke's) glycogen storage disease presents with a similar but more severe presentation as compared with type III, and displays increased blood lactate and severe hypoglycemia.
Answer 4: Type II (Pompe's) glycogen storage disease presents with cardiomegaly and early death from restrictive cardiomyopathy.
Answer 5: Type IV (Anderson) glycogen storage disease results from a lack of branching enzyme. (Remember: Anderson = can't Add branches). Presentation for this disorder also included hypotonia and cirrhosis, but the liver cannot form branched glycogen granules.