GSD Type 6

Also known as Hers Disease

Defect Results from a deficiency in the activity of one of several enzymes in phosphorylase-activating cascade (liver phosphorylase or phosphorylase b kinase)

Cause Mutation in genes PHKA2, PHKB, and PHKG2

Signs & Symptoms

• Typically exhibit prominent hepatomegaly (enlarged liver) but without spleen enlargement, growth retardation and variable but mild episodes of fasting hypoglycemia and hyperketosis (high blood ketones) during childhood. These clinical features and biochemical abnormalities generally resolve by puberty.
• High lactic acid and uric acid are characteristically absent.
• Delay in motor milestone may be noted in young children, and mild hypotonia and muscle weakness may be present, however in adolescence and adulthood, muscle strength and tone are usually normal.

Diagnosis

• Laboratory studies – Normal hypoglycemic response to fasting without increase in lactic acid.
• Imaging studies – CT or MRI of abdomen
• Liver biopsy – definitive
• Enzyme assay

Treatment

• Medical consult and management (ex. Cornstarch supplementation, avoidance of fasting)
• Diet – Although some patients have been given a high protein diet or supplementation of unsaturated fats, most patients require no dietary intervention.