Dried Blood Spot-Based Monitoring of Dietary Treatment in Children, Adolescents, and Young Adults with Inherited Disorders of Amino Acid Metabolism: A Four-Year Pilot Study

Background: Regular biochemical monitoring is essential for the safe and effective dietary treatment of inherited disorders of amino acid metabolism. However, conventional venous blood sampling may limit monitoring frequency and increase the burden on families. This study evaluated the feasibility and clinical usefulness of home-collected dried blood spot (DBS) samples analyzed using tandem mass spectrometry and additional chromatographic methods for dietary monitoring in inherited disorders of amino acid metabolism other than phenylketonuria. Methods: Between 2022 and 2025, children, adolescents, and young adults aged between 4 months and 20.5 years who were followed at a national metabolic center were monitored using DBS samples. The initial cohort included patients with maple syrup urine disease, tyrosinemia type III, homocystinuria, glutaric aciduria type 1, methylmalonic aciduria, isovaleric aciduria, argininosuccinic aciduria, methionine adenosyltransferase I/III deficiency, beta-ketothiolase deficiency, propionic aciduria, gyrate atrophy, and citrullinemia type 1. Disease-specific amino acids and metabolites were assessed to guide individualized dietary recommendations. Results: The number of monitored patients ranged from 24 to 40 per year. Overall annual completion rates of planned DBS measurements ranged from 56.7% to 73.0%, with additional clinically indicated samples collected in selected patients. DBS monitoring detected abnormal metabolite concentrations and supported dietary interventions, particularly in maple syrup urine disease, glutaric aciduria type 1, homocystinuria, tyrosinemia type III, and MAT I/III deficiency. In several other disorders, routine monthly DBS monitoring showed limited additional clinical value. Conclusions: DBS-based monitoring is a feasible approach that may support individualized dietary management in selected inherited disorders of amino acid metabolism, especially in early childhood and during periods of increased metabolic risk.