8199 Lifesaving Hypertrophic Cardiomyopathy in a Newborn with Transient Hyperinsulinism

Abstract Disclosure: L.B. Greenblatt: None. R. Spencer: None. O. Yeliosof: None. Introduction: Hyperinsulinism (HI) is the most common cause of persistent hypoglycemia in infants, and along with its FDA approved treatment, diazoxide, can pose cardiac morbidity. While HI can result in hypertrophic cardiomyopathy (HCM), diazoxide poses an increased risk of pulmonary hypertension (PH). Despite this, data suggest low rates of pre- and post-treatment echocardiograms being performed in infants treated with diazoxide. Clinical Case: A full term male was born SGA to a mother with no history of GDM via spontaneous vaginal delivery complicated by heavy meconium. Apgar scores were 1 and 9 at 1 and 5 minutes, respectively. The patient required positive pressure ventilation and was admitted to the NICU for hypoglycemia. Endocrine team was consulted on DOL 6 due to persistent hypoglycemia. Critical sample obtained at plasma glucose of 48 mg/dL showed detectable insulin and C-peptide, hypoketonemia, hypofattyacidemia and reassuring GH. Although cortisol was 7 ug/dL, ACTH stimulation testing revealed 60-minute cortisol of 18.1 ug/dL, making adrenal insufficiency unlikely. Glucagon stimulation test showed a positive response (delta of 42 mg/dL), confirming the diagnosis of HI. An echocardiogram prior to initiation of diazoxide showed normal anatomy with mild PH. The patient started diazoxide and chlorothiazide on DOL 8 and was discharged on DOL 13 with close outpatient follow up. He remained euglycemic with discontinuation of diazoxide by two months of age, highlighting the transient nature of his HI. Despite clinical improvement of HI, at one month of age his physical exam was notable for a new systolic murmur with echocardiography showing new moderate hypertrophy of the interventricular septum, consistent with HCM. There was preserved systolic function and no evidence of left ventricular outflow tract obstruction. At the time of this new finding, the family recalled history of sudden death in a paternal uncle at an early age. Genetic testing revealed autosomal dominant PKP2 mutation consistent with arrhythmogenic cardiomyopathy (AC), which results in progressive fibro-fatty replacement of the myocardium and is associated with arrhythmias and sudden cardiac death. The patient’s father was also found to have the same mutation. Subsequent echocardiograms showed resolution of HCM by three months of age. Conclusion: To our knowledge, this is the first report of transient congenital HI and reversible HCM in a patient with AC, which could be coincidental or could be a previously unrecognized association. Given the finding of AC, our patient requires lifelong monitoring for arrythmia and exercise restriction. Our case demonstrates the importance of cardiac evaluation and echocardiographic surveillance in children with HI treated with diazoxide. Given the association of HI with HCM irrespective of diazoxide, echocardiography should be considered in all neonates diagnosed with HI. Presentation: 6/2/2024