Glycogen synthase deficiency is a rare inborn error of metabolism, characterized by fasting hypoglycemia, hypoglycemic seizures, and ketonuria. Only 7 families with 14 affected children have been reported. Here, we report an additional patient with this deficiency. Findings in this patient were clinically and biochemically consistent with those reported in patients with ketotic hypoglycemia and may alert the clinician to consider glycogen synthase deficiency.
A 5-year-old girl had hypoglycemia and was of short stature. Studies of pituitary function demonstrated combined growth hormone and adrenocorticotropic hormone (ACTH) deficiency. She was shown to have ketotic hypoglycemia. In contrast to patients previously reported with hypopituitarism and ketotic hypoglycemia, she had no deficiency of gluconeogenic substrate. Serum levels of alanine and other gluconeogenic amino acids were normal during fasting and hypoglycemia. These studies suggest that inadequate gluconeogenic precursors are not the cause of her ketotic hypoglycemia. Ketotic hypoglycemia in association with hypopituitarism may be secondary to multiple biochemical defects.