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Synonyms:
Liver Phosphorylase Deficiency, Hers Disease
The phosphorylase enzyme plays a vital role in the breakdown of glycogen into glucose. With a deficiency of the liver phosphorylase enzyme, glycogen cannot be broken down to glucose, and the accumulating glycogen results in an enlarged liver. A total deficiency of this liver enzyme would not likely be compatible with life, thus patients with Type VI GSD actually have only partial deficiency of the enzyme.
Clinically, this form of glycogen storage disease appears to be similar to, but is usually considerably milder than glucose-6-phosphatase deficiency GSD (type I GSD). Extreme enlargement of the liver, growth retardation, and mild hypoglycemia are seen, but patients can certainly present with few symptoms and be able to lead normal lives.
The diagnosis of this disease is based on liver biopsy material; assays must be done for glycogen content (which is increased) as well as for phosphorylase activity. Phosphorylase activity in the liver tissue is present but reduced.
Due to the mildness of the clinical findings, treatment is usually not required. Should hypoglycemia and growth failure be a major problem, these patients should receive the same nutritional management that has been effective in Type I GSD and Type III GSD.
Links:
Hers Disease from National Organization for Rare Disorders [NORD]
OMIM GSD Type VI info on Online Mendelian Inheritance in Man searchable database
Type VI GSD info from eMedicine
Hers Disease from Madisons Foundation
This page was created in June 2001.
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