Natural History of the Hyperinsulinism Hyperammonemia Syndrome – A Retrospective Review Incorporating Patient-centered Data

INTRODUCTION: The hyperinsulinism hyperammonemia (HI/HA) syndrome manifests with fasting and protein-induced hypoglycemia, hyperammonemia, and neurodevelopmental features including epilepsy. There is a paucity of information describing the natural history of the HI/HA syndrome. METHODS: A retrospective review of patients with HI/HA syndrome evaluated at the Congenital Hyperinsulinism Centers at the Children's Hospital of Philadelphia or Cook Children's Medical Center or who contributed to the Congenital Hyperinsulinism International HI Global Registry (HIGR) was conducted to describe the natural history of the HI/HA syndrome with particular focus on treatment and neurodevelopmental outcomes. RESULTS: A total of 66 patients (36 female) from the medical record review and 15 patients (7 female, 3 sex not reported) from HIGR were included. Median age at last follow-up was 13.1 years (IQR, 6.8-19.0 years) in the medical record cohort and median age at survey completion was 11.6 years (IQR, 5.5-18.0 years) among HIGR participants. Eighty percent of the medical record cohort and 82% of HIGR participants were treated with diazoxide and most continued treatment over the follow-up period. Epilepsy (29% of medical record cohort, 33% HIGR participants) and neurodevelopmental issues (64% medical record cohort, 73% HIGR participants) were common. CONCLUSIONS: Our findings underscore the importance of longitudinal endocrine and neuropsychological follow-up for patients with HI/HA syndrome and demonstrate the potential value of patient-driven registry data to address persistent knowledge gaps in the natural history of rare diseases.