Ana S. P. Moreira

Medium‐chain acyl‐CoA dehydrogenase deficiency (MCADD) is the most prevalent mitochondrial fatty acid β‐oxidation disorder. In this study, we assessed the variability of the lipid profile in MCADD by analysing plasma samples obtained from 25 children with metabolically controlled MCADD (following a normal diet with frequent feeding and under l ‐carnitine supplementation) and 21 paediatric control subjects (CT). Gas chromatography–mass spectrometry was employed for the analysis of esterified fatty acids, while high‐resolution C18‐liquid chromatography‐mass spectrometry was used to analyse lipid species. We identified a total of 251 lipid species belonging to 15 distinct lipid classes. Principal component analysis revealed a clear distinction between the MCADD and CT groups. Univariate analysis demonstrated that 126 lipid species exhibited significant differences between the two groups. The lipid species that displayed the most pronounced variations included triacylglycerols and phosphatidylcholines containing saturated and monounsaturated fatty acids, specifically C14:0 and C16:0, which were found to be more abundant in MCADD. The observed changes in the plasma lipidome of children with non‐decompensated MCADD suggest an underlying alteration in lipid metabolism. Therefore, longitudinal monitoring and further in‐depth investigations are warranted to better understand whether such alterations are specific to MCADD children and their potential long‐term impacts.