Biotinidase deficiency (BD) is a rare autosomal recessive metabolic disease. Previously the disease was identified only by clinical signs and symptoms, and since recently, it has been included in newborn screening programs (NBS) worldwide, though not commonly. In Europe, BD prevalence varies highly among different countries, e.g., from 1:7 116 in Turkey to 1:75 842 in Switzerland. This paper aimed to present the molecular spectrum of BD (profound and partial forms) in Polish patients diagnosed within the national NBS of 1,071,463 newborns. The initial suspicion of BD was based on an abnormal biotinidase activity result determined in a dry blood spot (DBS) by colorimetric and by fluorimetric methods while biochemical verification was determined by serum biotinidase activity (as quantitative analysis). The final diagnosis of BD was established by serum enzyme activity and the BTD gene direct sequencing. The obtained results allowed for the estimation of disease prevalence (1:66,966 births, while 1:178,577 for profound and 1:107,146 for partial forms), and gave novel data on the molecular etiology of BD.

Introduction To avoid the risk of intellectual disabilities, newborns in Poland are screened for phenylketonuria and are recommended to start a life-long phenylalanine-restricted diet shortly after birth. The aim of this paper is to evaluate the health care for patients with classical...

Introduction Patients with disorders of aromatic amino acid metabolism are a heterogeneous group. They vary in morbidity and medical care requirements. Polish newborn screening program allows for quick diagnosis of some inborn errors of metabolism (such as classical phenylketonuria, mild...

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an inborn error of metabolism resulting in the absence or reduced activity of the enzyme responsible for the β-oxidation of medium-chain fatty acids. MCAD deficiency can lead to metabolic decompensation, presenting as hypoketotic hypoglycaemia, hepatic encephalopathy (Reye-like syndrome), or death regardless of the patient's age. Blood samples in the national newborn screening programme were collected using 903 filter paper (dry blood spot - DBS). Routine dried blood spots from newborn screening (NBS) were analysed by flow injection and derivatised tandem mass spectrometry method (MS/MS). Positive screening cases in the MCAD deficiency profile were verified through GC/MS urine organic acid profiling and enzymatic and/or molecular testing. A total of 3,806,166 newborns were screened between 2014-2024, resulting in the identification of 94 cases of MCAD deficiency. Analysis of the obtained results revealed a consistent pattern in the levels of octanoylcarnitine (C8), hexanoylcarnitine (C6), and decanoylcarnitine (C10) acylcarnitines, as well as the C8/C10 ratio across these cases. Only one case of confirmed MCAD deficiency with an atypical acylcarnitine profile was found. The use of tandem mass spectrometry has enabled the inclusion of MCAD deficiency in newborn screening programmes. This has facilitated early detection, diagnosis, and initiation of therapeutic interventions to prevent metabolic decompensation. We emphasize the need for repeated sampling and further testing if C8 is even slightly elevated.

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.