Extended Risk of Mortality in Children with Inborn Errors of Metabolism: A Longitudinal Cohort Study

Objectives To determine the long-term risk of mortality among children with inborn errors of metabolism. Study design We conducted a retrospective cohort study of 1750 children with inborn errors of metabolism (excluding mitochondrial disorders) and 1 036 668 children without errors of metabolism who were born in Quebec, Canada, between 2006 and 2019. Main outcome measures included all-cause and cause-specific mortality be-tween birth and 14 years of age. We used adjusted survival regression models to estimate HRs and 95% CIs for the association between inborn errors of metabolism and mortality over time. Results Mortality rates were greater for children with errors of metabolism than for unaffected children (69.1 vs 3.2 deaths per 10000 person-years). During 7 702 179 person-years of follow-up, inborn errors of metabolism were associated with 21.2 times the risk of mortality compared with no error of metabolism (95% CI 17.23-26.11). Dis-orders of mineral metabolism were associated with greater mortality the first 28 days of life (HR 60.62, 95% CI 10.04-365.98), and disorders of sphingolipid metabolism were associated with greater mortality by 1 year (HR 284.73, 95% CI 139.20-582.44) and 14 years (HR 1066.00, 95% CI 298.91-3801.63). Errors of metabolism were disproportionately associated with death from hepatic/digestive (HR 208.21, 95% CI 90.28-480.22), respiratory (HR 116.57, 95% CI 71.06-191.23), and infectious causes (HR 119.83, 95% CI 40.56-354.04). Conclusions Children with errors of metabolism have a considerably elevated risk of mortality before 14 years, including death from hepatic/digestive, respiratory, and infectious causes. Targeting these causes of death may help improve long-term survival. (J Pediatr 2023;252:16-21).