What is GSD?
Type IV Glycogen Storage Disease
Overview:
- Synonyms: Brancher Deficiency, Andersen Disease, Amylopectinosis, Adult Polyglucosan Body Disease (APBD)
- Cause: Mutations in the GBE1 gene results in deficiency of glycogen branching enzyme
- Incidence: 1 in 600,000 – 800,000
- Effect: Abnormal glycogen with long branches results in scarring of affected organs
Subtypes:
The severity and manifestations depend on the organs involved and the amount of enzyme activity present.
| Subtype | Organs Involved | Presentation |
| Perinatal Neuromuscular | Muscle, liver | Presents in-utero with decreased fetal movements, fetal hydrops;
Perinatal distress |
| Congenital Neuromuscular | Muscle | Profound hypotonic,
respiratory distress, dilated cardiomyopathy |
| Hepatic | Liver | Hepatomegaly,
AST/ALT elevation, Failure to thrive |
| Childhood Neuromuscular | Muscle | Muscle weakness
Dilated cardiomyopathy |
| APBD | Brain, spinal Cord, nerves | Neuropathy, weakness, cognitive impairment presenting in adults |
Diagnosis:
- Based on clinical symptoms
- Genetic testing: Identifies mutations in the GBE1 gene
- Detection of abnormal glycogen structure and branching enzyme deficiency can be seen on a biopsy
Treatment:
- Treatment depends on the tissue involved and the presence of partial enzyme activity
- Strict restriction of carbohydrate to minimize glycogen storage may be beneficial
- Low dose cornstarch may be helpful with the strict diet to prevent ketosis
- A high protein diet may be helpful
- Liver transplant is required in the severe, progressive hepatic form
- Multisystem involvement requires ongoing care
- Annual ultrasounds to screen for cirrhosis in the liver forms
- Echocardiograpms (every 3-6 months) in infancy and early childhood; annually in later childhood and adults
- Labs: Liver function tests, CK, coagulation studies, ketone monitoring, protein, albumin, and prealbumin
Prognosis:
- Poor in infantile, progressive form without a liver transplant
- Non-progressive hepatic subtypes are doing well with dietary therapy
- Recent trials in APBD have shown promise
