Glycogen storage disease type III presenting with secondary diabetes and managed with insulin: a case report

INTRODUCTION: Reports of secondary diabetes in glycogen storage disease type III have been very limited, where the pathogenesis and management have not been clear. Here we report on a rare case of secondary diabetes in glycogen storage disease type III that has been successfully managed with insulin. CASE PRESENTATION: This is a 19-year-old female of Egyptian ethnicity, born of a consanguineous marriage and known to have glycogen storage disease type III since the age of 2½ years. She presented to us with a history of polyuria, polydipsia, and loss of weight of a few days duration. Physical exam showed stunted growth, hepatomegaly, myopathy and mild dehydration. Emergency labs revealed a fasting blood glucose of 276 mg/dl, but with no ketonuria and arterial blood gases were essentially normal. Her liver transaminases were mildly elevated at the time. Review of her records revealed that the diagnosis of glycogen storage disease type III was made at the age of 2½ when the mother reported repeated attacks of afebrile (hypoglycemic) convulsions, increasing abdominal girth and failure to thrive. The diagnosis was confirmed by demonstration of debrancher enzyme deficiency on enzymatic assay. Over the years she developed liver dysfunction along with other complications and subsequently her hypoglycemic attacks disappeared a few years prior to her current presentation. After careful consideration of different treatment options, and considering she had been free of hypoglycemic attacks for a few years and had liver dysfunction, we chose to cautiously initiate the patient on insulin therapy. She was still poorly controlled and we gradually increased her total daily dose to 0.8 u/kg. She continued to be free of hypoglycemic attacks and her average daily blood glucose is about 160 mg/dl. CONCLUSION: We report a rare case of secondary diabetes mellitus in a patient with glycogen storage disease type III managed with insulin. We recommend insulin therapy over oral hypoglycemics to avoid further hepatotoxicity, provided hypoglycemia has resolved. We also recommend serial follow up of glycogen storage disease type III patients with an oral glucose tolerance test for early detection and management of glucose intolerance.