Postprandial Hypoglycemia in a Patient With Clinical Beckwith-Wiedemann Syndrome

A male neonate exhibited hallmark features of Beckwith-Wiedemann syndrome (BWS) including large for gestational age, macroglossia, multiple ear pits, and umbilical hernia. He had neonatal hypoglycemia, requiring a glucose infusion rate of 9.7 mg/kg/min. Over time, he demonstrated persistent hypoglycemia with point-of-care glucose <60 mg/dL (<3.3 mmol/L) (70-140 mg/dL, 3.9-7.8 mmol/L) prompting a critical sample. A diagnostic fast of 13 hours revealed no hypoglycemia <50 mg/dL. However, he was found to have postprandial hypoglycemia after 2 hours to 58 mg/dL (3.2 mmol/L) (70-140 mg/dL, 3.9-7.8 mmol/L) with low β-hydroxybutyrate of <1.8 mg/dL (<0.17 mmol/L) (>3.6 mg/dL, >1.8 mmol/L) and increased insulin 3.9 μIU/mL (27 pmol/L) (2-13 μIU/mL; 14-90 pmol/L). Low-dose diazoxide (6 mg/kg/day) and chlorothiazide (10 mg/kg/day) were initiated. After 48 hours on diazoxide, all episodes of postprandial hypoglycemia resolved. A safety fast on diazoxide sustained blood glucose >70 mg/dL with a rise in serum β-hydroxybutyrate at 13 and 19 hours. Our case highlights the heterogeneity of hypoglycemia in BWS, either fasting or postprandial. This emphasizes the importance of appropriate screening for both forms of hypoglycemia in patients with BWS and that diazoxide is an effective treatment.