MON-105 A Case Report of Neonatal Hyperinsulinism in an Infant with Turner Syndrome Successfully Treated with Diazoxide

BACKGROUND: Only four previous cases of hyperinsulinemic hypoglycemia have been reported in association with Turner Syndrome. All of these cases involved young females with a mosaic form of Turner Syndrome involving a ring X chromosome; an abnormality found in just 16% of Turner Syndrome karyotypes. Two of these cases showed responsiveness to diazoxide which stabilized their blood glucose levels and allowed for a longer fasting tolerance. Clinical Case: A 5 day old female who was born at 36 weeks and 1 day with Turner Syndrome was referred to pediatric endocrinology for persistent episodes of hypoglycemia. Patient was started on D10W with electrolytes at an outside hospital due to hypoglycemia and was transferred to the NICU at day of life 3. D10W was discontinued on day of life 5 due to adequate PO feeding and reassuring blood glucose readings. Blood glucose was monitored every 4 hours and infant continued to have episodes of asymptomatic hypoglycemia typically in the mid-low 40’s, with one episode of low blood sugar to 36 mg/dl. Due to a concern for hyperinsulinism, labs were drawn at a serum blood glucose of 46mg/dl. The infant was found to have a beta-hydroxybutyrate of 0.2 (0.0-0.8mmol/L) and insulin of 1.0 (2.0–19.6uIU/mL). Hyperinsulinism was thus confirmed by the presence of inappropriately low ketones and inappropriately normal insulin in the setting of hypoglycemia. We initiated the patient on 7.5mg diazoxide BID (5.9mg/kg/day total) and was highly responsive to diazoxide. After her third dose (36 hours into treatment), her hypoglycemia had resolved and blood sugar readings had normalized. Patient was discharged home with a glucometer and instructions for the mother to call if blood glucose was less than 60. The patient has been stable on diazoxide with no reported episodes of hypoglycemia. Interestingly, her genetic testing demonstrated a complex chromosomal microarray pattern on chromosome X, a mosaicism with 2 cell lines: 1 with monosomy X and 1 cell line with a normal X chromosome with a ringed X chromosome. Conclusion:This is a case demonstrating the efficacy of diazoxide in the management of asymptomatic hyperinsulinemic hypoglycemia in a neonate with Turner Syndrome with a ring X chromosome. References: Cappella M, Graziani V, Pragliola A, et al. Hyperinsulinemic Hypoglycaemia in a Turner Syndrome with Ring (X). Case Rep Pediatr 2015; 2015:561974.