Clinical Analysis of Secondary Carnitine Deficiency in Pediatric Patients at a Single Institution

Background: Carnitine is a conditionally essential amino acid that is primarily obtained through dietary intake, and is synthesized endogenously in the liver, kidneys, and brain.It plays a crucial role in fatty acid metabolism, particularly in skeletal and cardiac muscles.Objective: In this study, we retrospectively evaluated the clinical features and therapeutic responses of pediatric patients diagnosed as having secondary carnitine deficiency at our institution.Methods: Medical records of 213 pediatric patients who underwent carnitine level testing between January 2017 and December 2021 were reviewed.Of these, 77 patients were identified as having either carnitine deficiency (free carnitine < 20 μmol/L) or being at high risk of developing carnitine deficiency (free carnitine 20-36 μmol/L, with an acylcarnitine-to-free carnitine [AC/FC] ratio > 0.4).Pre-supplementation and post-supplementation FC levels and AC/FC ratios were analyzed.Statistical significance was assessed using the Mann-Whitney U test.Results: Substantial improvements in both FC levels and AC/FC ratios were observed following carnitine supplementation, particularly among patients with ketotic hypoglycemia and metabolic disorders.In addition, those with a history of pivalate-conjugated antibiotic use demonstrated notably low FC levels and favorable responses to carnitine supplementation.Conclusion: The monitoring of FC levels and AC/FC ratios is essential for pediatric patients at high risk of developing secondary carnitine deficiency.Early carnitine supplementation, tailored to the underlying condition and its severity, is particularly beneficial for patients with ketotic hypoglycemia and those receiving pivalate-conjugated antibiotics.