Abstract
Introduction: Biotinidase deficiency (BD) is an autosomal recessive disease causing a defect in the biotin-releasing enzyme. Newborn screening (NBS) allows early diagnosis and treatment, ensuring excellent prognosis. The aim of this study was to describe our experience in the diagnosis, treatment, and follow-up showing key strategies and unsolved questions of the management of BD patients.Methods: We analyzed data of patients identified by the Regional Centre for Newborn Screening of Verona and followed by the Inherited Metabolic Disease Unit of Verona and Neonatal Intensive Care Unit of Bolzano, Italy, from 2014 to 2020.Results: Thirty-seven patients were diagnosed by NBS (five profound and 32 partial BD), with a total incidence of 1:5,996. All were started on biotin at diagnosis and presented no symptoms at follow-up. Analysis of parents and siblings led to identification of five asymptomatic patients with partial BD: one asymptomatic parent and four young siblings. Genetic analysis of the BTD gene identified 17 different genotypes and one mutation not previously known.Discussion: Our data confirm that NBS introduction had a dramatic impact on BD diagnosis, and the incidence has increased significantly compared to other areas. Partial defects are more common than profound and have a distinctive genotype. Partial BD treatment is still controversial even at what dose of biotin and for how long. At the end, BD treatment is very easy and inexpensive and prevents severe neurological damage. Sharing experiences is essential to achieving guidelines for treatment and follow-up and a better genotype–phenotype correlation.
Highlights
Biotinidase deficiency (BD) is an autosomal recessive disease causing a defect in the biotin-releasing enzyme
Newborn screening (NBS) for BD have been performed since 1986 at the Regional Center for Neonatal Screening, Diagnosis and Treatment of Inherited Congenital Metabolic and Endocrinological Diseases of Verona covering North East of Italy while, from 2014, the Inherited Metabolic Diseases Unit is actively involved in treatment and follow-up of children diagnosed with total and partial biotinidase deficiency
Among 293,784 newborns screened by the Regional Screening Centre of Verona since 2014 until the end of 2020, 287 were recalled to repeat dried blood spots (DBS) in cases of suspected BD and 49 were diagnosed with BD, with a total incidence of 1:5,996 newborns
Summary
Biotinidase deficiency (BD) is an autosomal recessive disease causing a defect in the biotin-releasing enzyme. Newborn screening (NBS) allows early diagnosis and treatment, ensuring excellent prognosis. The aim of this study was to describe our experience in the diagnosis, treatment, and follow-up showing key strategies and unsolved questions of the management of BD patients. Biotinidase deficiency (BD, OMIM: 253260) is an autosomal recessive disease caused by an altered activity of the enzyme biotinidase. Biotinidase releases biotin from biocytin or small biotinylated peptides downstream the proteolytic turnover of holocarboxylases and other biotinylated proteins. Patients may present metabolic complications as well, like lactic acidosis, ketoacidosis, and hyperammonemia, and less frequently organic aciduria (5). Some patients may present respiratory problems, such as hyperventilation, laryngeal stridor, and apnea (4)
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