A case of glycogen storage disease type I associated with an incomplete type of Fanconi syndrome; the protective role of lysosomal alpha 1,4-glucosidase and insulin deficiency against hypoglycemia.

A 59-year-old Japanese farmer with asymptomatic fasting hypoglycemia and with exaggerated hypoglycemic episodes induced by insulin and oral hypoglycemic agent administered for his postprandial hyperglycemia was diagnosed as glycogen storage disease type I. This diagnosis was suggested by unresponsiveness of blood glucose level to glucagon and confirmed by 13% normal level of glucose 6-phosphatase activity in liver biopsy specimen and by the presence of PAS positive amylase digestable glycogen in liver specimen. This case was associated with an incomplete type of Fanconi syndrome characterized by hyperphosphaturic hypophosphatemia, partial aminoaciduria, mild proteinuria and hyperuricosuric normouricemia in spite of the lactic acidemia due to glycogen storage disease type I. The etiology for the absence of hypoglycemia and other typical manifestations of glycogen storage disease type I was studied. The glucose production from glycogen by lysosomal alpha 1,4-glucosidase especially at prolonged fasting and the presence of postprandial hyperglycemia by insulin deficiency are regarded as responsible for keeping this patient free from typical manifestations of glycogen storage disease type I.