GSD Type 9

Defect: Deficiency of an associated kinase that activates the enzymes that converts glycogen to glucose.

Cause: Inherited or X-linked as an autosomal-recessive disorder involving multiple genes that form the large four-subunit enzyme. (Like a four piece part of a machine that needs to fit together to do it’s job).

Incidence: Occurs in approximately in 1 in 100,000 births and accounts for 25% of all GSDs.

Signs & Symptoms

• Hypoglycemia with increased blood ketones during fasting but generally milder than GSD I & III.
• Enlarged liver and short stature are common but may be of different severity.
• Mild increase in blood lipids (fats) and serum transaminases (an enzyme involved in metabolism) can occur but lactic acid and uric acid are normal.
• Muscle involvement can occur with poor muscle tone, myoglubinuria (oxygen transporters in the muscles abnormally present in the patient’s urine), and muscle weakness.

Diagnosis

• Biopsies of affected tissues showing abnormal enzyme activities – most definite diagnostic tool/definitive.
• Because of multiple gene involvement, mutation analysis cannot fully rule out GSD IX.

Treatment

• Prognosis is excellent and most patients do not require specific treatment except for avoidance of fasting and routine consumption of bedtime snack.
• In some patient who experiences overnight hypoglycemia, uncooked cornstarch at bedtime is recommended.