Frequent Inborn Errors Of Metabolism Research Articles

A typical phenotypes due to NDUFV1 mutations

Mitochondria have a critical role in energy metabolism, generating and scavenging of free radicals, intracellular Ca2+ regulation, and cell mitophagy. Dysfunction of the mitochondrial oxidative phosphorylation complex is the most frequent inborn errors of metabolism. Mitochondrial diseases are highly diverse in etiology, age of the disease onset, involvement of multiple organ systems, and genetic causes. NDUFV1 is a core subunit of mitochondrial Complex I (CI), and mutations cause CI deficiency. Clinically, CI deficiency is associated with severe infantile lactic acidosis, cardiomyopathy, encephalomyopathy, leukoencephalopathy, and Leigh syndrome. The cellular biology and molecular mechanisms of mitochondrial diseases are still elusive due to the heterogeneous genetic background and lack of phenotype-genotype correlation. Neurological abnormalities are the second most frequent presentations of mitochondrial diseases, including white matter abnormalities, psychomotor regression, and mental disability. The defects in myelin sheath or glial cells cause leukodystrophy which is a progressive genetical syndrome. To date, no therapy is available to cure mitochondrial diseases; exploration of the phenotype and molecular background are crucial for disease diagnosis, supportive treatments, proper genetic counselling, prenatal diagnosis, and experimental treatments. This article underscores the atypical clinical presentations of NDUFV1 mutations and the importance of a multidisciplinary approach to correlate phenotypes, biochemical, radiological, and molecular diagnosis. Implementation of multidisciplinary approach will enhance the possibility of discovering the therapeutic targets to treat mitochondrial disorders and ensure prenatal diagnosis to prevent inherited diseases.

Organic Acidurias in Egyptian children: The urge for high-risk screening.

Organic acidurias are a group of inborn errors of metabolism with a significant diagnostic challenge and serious morbidities and mortalities. They are considered the most frequent inborn errors of metabolism among high-risk children. Gas chromatography-Mass spectrometry is a reliable diagnostic technique for organic acidurias. This hospital-based study aimed to quantify the frequency of organic acidurias among a group of high-risk Egyptian pediatric patients, and to highlight the importance of the high-risk screening for such disorders. One hundred fifty high-risk children presented to the inherited metabolic disease unit and the pediatric intensive care units of Cairo University Children Hospital were tested for urine organic acids using Gas chromatography-Mass spectrometry. 45/150 (30%) patients confirmed to have altered organic acids profile. Neurological manifestations were the most common presentation. Glutaric aciduria type I and Maple syrup urine disease were the most common disorders encountered among the studied group. Organic acid detection by Gas chromatography-Mass spectrometry is a key to the diagnosis of many metabolic disorders. Until a national expanded newborn screening program is established, high-risk screening is highly encouraged for the early detection and proper intervention of such disorders among the Egyptian children.

Multi-omics in classical galactosemia: Evidence for the involvement of multiple metabolic pathways.

Classical galactosemia (CG) is one of the more frequent inborn errors of metabolism affecting approximately 1:40.000 people. Despite a life-saving galactose-restricted diet, patients develop highly variable long-term complications including intellectual disability and movement disorders. The pathophysiology of these complications is still poorly understood and development of new therapies is hampered by a lack of valid prognostic biomarkers. Multi-omics approaches may discover new biomarkers and improve prediction of patient outcome. In the current study, (semi-)targeted mass-spectrometry based metabolomics and lipidomics were performed in erythrocytes of 40 patients with both classical and variant phenotypes and 39 controls. Lipidomics did not show any significant changes or deficiencies. The metabolomics analysis revealed that CG does not only compromise the Leloir pathway, but also involves other metabolic pathways including glycolysis, the pentose phosphate pathway, and nucleotide metabolism in the erythrocyte. Moreover, the energy status of the cell appears to be compromised, with significantly decreased levels of ATP and ADP. This possibly is the consequence of two different mechanisms: impaired formation of ATP from ADP possibly due to reduced flux though the glycolytic pathway and trapping of phosphate in galactose-1-phosphate (Gal-1P) which accumulates in CG. Our findings are in line with the current notion that the accumulation of Gal-1P plays a key role in the pathophysiology of CG not only by depletion of intracellular phosphate levels but also by decreasing metabolite abundance downstream in the glycolytic pathway and affecting other pathways. New therapeutic options for CG could be directed towards the restoration of intracellular phosphate homeostasis.

The Prevalence and Incidence of Congenital Phenylketonuria in 59 Countries: A Systematic Review

Context: Phenylketonuria (PKU) is the most frequent inborn error of metabolism, in which newborns cannot metabolize phenylalanine to tyrosine. Increased phenylalanine in untreated patients with PKU can cause serious intellectual disability; its onerous financial burden also falls on societies. This review study aimed to systematically indicate the frequency of PKU worldwide. We also intended to highlight the global prevalence of PKU, which might shed light on better clinical management and screening programs. Methods: In this systematic review, two electronic databases, including PubMed and ScienceDirect were searched for the related literature using relevant keywords: “Phenylketonuria” or “PKU” and “Prevalence” or “Incidence” and “Iran” or “Middle East” or “Europe” or “America” or “Asia.” Accordingly, 4306 reports conducted on PKU from January 2007 to December 2018 were retrieved. With the removal of 44 duplicated publications, 44 reports were included in the current systematic review. Prevalence and incidence rates were categorized based on different continents in which nations used various NBS programs to report the incidence and prevalence of PKU. Non-English, non-eligible, duplicated, animal, and in vitro studies are excluded. Results: Based on the reported quantitative data, the prevalence of PKU diagnosed worldwide ranged from 0.00044% to 0.02736% in which Italy possessed the highest prevalence; however, Thailand manifested the lowest prevalence rate. However, for some countries, such as India or Finland, either the related data to the frequency of PKU was outdated or overlooked applying any newborn screening programs respecting PKU. Conclusions: The current study revealed an elevated prevalence of PKU in Iran, compared with other Asian countries; thus, it demands a more serious management program. Moreover, the high prevalence of PKU in European countries should not be underestimated.

Mitochondrial disorders of the OXPHOS system.

Mitochondrial disorders are among the most frequent inborn errors of metabolism, their primary cause being the dysfunction of the oxidative phosphorylation system (OXPHOS). OXPHOS is composed of the electron transport chain (ETC), formed by four multimeric enzymes and two mobile electron carriers, plus an ATP synthase [also called complex V (cV)]. The ETC performs the redox reactions involved in cellular respiration while generating the proton motive force used by cV to synthesize ATP. OXPHOS biogenesis involves multiple steps, starting from the expression of genes encoded in physically separated genomes, namely the mitochondrial and nuclear DNA, to the coordinated assembly of components and cofactors building each individual complex and eventually the supercomplexes. The genetic cause underlying around half of the diagnosed mitochondrial disease cases is currently known. Many of these cases result from pathogenic variants in genes encoding structural subunits or additional factors directly involved in the assembly of the ETC complexes. Here, we review the historical and most recent findings concerning the clinical phenotypes and the molecular pathological mechanisms underlying this particular group of disorders.

Biochemical Screening of Intellectually Disabled Patients: A Stepping Stone to Initiate a Newborn Screening Program in Pakistan.

Inborn errors of metabolism (IEMs) are rare group of genetic disorders comprising of more than 1,000 different types. Around 200 of IEMs are potentially treatable through diet, pharmacological and other therapies, if diagnosed earlier in life. IEMs can be diagnosed early through newborn screening (NBS) programs, which are in place in most of the developed countries. However, establishing a NBS in a developing country is a challenging task due to scarcity of disease related data, large population size, poor economy, and burden of other common disorders. Since, not enough data is available for the prevalence of IEMs in Pakistan; therefore, in this study, we set out to find the prevalence of various treatable IEMs in a cohort of intellectually disabled patients suspected for IEMs, which will help us to initiate a NBS program for the most frequent IEMs in Pakistan. Therefore, a total of 429 intellectually disabled (IQ <70) patient samples were collected from Pakistan. A subset of 113 patient samples was selected based on the clinical information for the detailed biochemical screening. Advance analytical techniques like, Amino Acid Analyzer, GC-MS, UHPLC-MS, and MS/MS were used to screen for different treatable IEMs like aminoacidopathies, fatty acid β-oxidation disorders and mucopolysaccharidoses (MPS) etc. A total of 14 patients were diagnosed with an IEM i.e., 9 with homocystinuria, 2 with MPS, 2 with Guanidinoacetate methyltransferase (GAMT) deficiency and 1 with sitosterolemia. These IEMs are found frequent in the collected patient samples from Pakistan. Thus, present study can help to take an initiative step to start a NBS program in Pakistan, especially for the homocystinuria having highest incidence among aminoacidopathies in the studied patients, and which is amenable to treatment. This endeavor will pave the way for a healthier life of affected patients and will lessen the burden on their families and society.

Screening for organic acidurias and aminoacidopathies in high-risk Brazilian patients: Eleven-year experience of a reference center.

Organic acidurias and aminoacidopathies are groups of frequent inborn errors of metabolism (IEMs), which are caused by mutations in specific genes that lead to loss of protein/enzyme or transport function with important deleterious effects to cell metabolism. Since a considerable number of such disorders are potentially treatable when diagnosed at an early stage of life, diagnosis is crucial for the patients. In the present report, we describe symptomatic individuals referred to our service that were diagnosed with these disorders from 2006 to 2016. We used blood and urine samples from 21,800 patients suspected of aminoacidopathies or organic acidemias that were processed by the analytical techniques reverse phase high-performance liquid chromatography for amino acid quantification and gas chromatography coupled to mass spectrometry for organic acid detection. Analysis of dried blood spots by liquid chromatography-tandem mass spectrometry was used in some cases. We detected 258 cases of organic acidurias, and 117 patients with aminoacidopathies were diagnosed. Once diagnosis was performed, patients were promptly submitted to the available treatments with clear reduction of mortality and morbidity. The obtained data may help pediatricians and metabolic geneticists to become aware of these diseases and possibly expand newborn screening programs in the future.

The impact of consanguinity on the frequency of inborn errors of metabolism

Inborn errors of metabolism (IEM) are a heterogeneous group of genetic disorders present in all ethnic groups. We investigated the frequency of consanguinity among parents of newborns with IEM diagnosed by neonatal screening.Data were obtained from 15years of expanded newborn screening for selected IEM with autosomal recessive mode of inheritance, a national screening program of newborns covering the period from 2002 until April 2017. Among the 838,675 newborns from Denmark, the Faroe Islands and Greenland, a total of 196 newborns had an IEM of whom 155 from Denmark were included in this study. These results were crosschecked against medical records. Information on consanguinity was extracted from medical records and telephone contact with the families.Among ethnic Danes, two cases of consanguinity were identified in 93 families (2.15%). Among ethnic minorities there were 20 cases of consanguinity among 33 families (60.6%). Consequently, consanguinity was 28.2 times more frequent among descendants of other geographic place of origin than Denmark. The frequency of consanguinity was conspicuously high among children of Pakistani, Afghan, Turkish and Arab origin (71.4%). The overall frequency of IEM was 25.5 times higher among children of Pakistani, Turkish, Afghan and Arab origin compared to ethnic Danish children (5.35:10,000 v 0.21:10,000). The frequency of IEM was 30-fold and 50-fold higher among Pakistanis (6.5:10,000) and Afghans (10.6:10,000), respectively, compared to ethnic Danish children.The data indicate a strong association between consanguinity and IEM. These figures could be useful to health professionals providing antenatal, pediatric, and clinical genetic services.

Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis.

Selenium binding protein1 (SELENBP1) has been associated with several cancers. Its exact role was unknown. We show that SELENBP1 is a methanethiol oxidase (MTO), related to MTO of methylotrophic bacteria, converting methanethiol to H2O2, formaldehyde and H2S, an activity not known to exist in humans. Mutations in SELENBP1 were found in five patients with a cabbage-like smelling breath. Increased levels of methanethiol and dimethylsulfide are the main odorous compounds in their breath and responsible for the malodor. Increased urinary excretion of dimethylsulfoxide is a diagnostic biomarker of MTO-deficiency. Patient fibroblasts showed reduced amounts of SELENBP1 protein and deficient MTO enzymatic activity which could be restored by lentiviral-mediated expression of the wild-type SELENBP1 gene. A knockout mouse line showed the same biochemical characteristics. Our data define a novel inborn error of metabolism caused by MTO-deficiency leading to a malodor syndrome. MTO deficiency may be a frequent inborn error of metabolism.

Selective Screening for Inborn Errors of Metabolism: A Report of Six Years Experience

Background: Tandem MS analysis of dried blood spots is a widely used method for diagnosis of inborn errors of metabolism. Clinical laboratories performing this test for clinically suspected children at different ages are faced with the challenge of using appropriate reference ranges for the diagnostic markers. Objectives: Retrospective evaluation of laboratory data was performed to establish the disease spectrum and clinically relevant reference ranges for the diagnostic markers. Methods: The results of clinically suspected 4800 patients were extracted from laboratory information system and correlated with clinical data. Relevant reference ranges for the analytes in dried blood spots was determined using nonparametric statistical methods. Results: Forty four patients were diagnosed with 12 different inborn errors of metabolism. There were 23 patients with organic acid disorder, 13 patients with amino acid or urea cycle disorder and 8 patients with fatty acid oxidation disorder. The reference ranges were significantly different between the children under and over 1 year of age for some acylcarnitines (C0, C2, C3, C5OH, C14, C16 and C18) and amino acids (citrulline, arginine, tyrosine, valine and leucine). Conclusions: The interpretation of the Tandem MS analysis results showed that the difference in the reference ranges for children under or over one year of age did not affect the diagnosis for most frequent inborn errors of metabolism.

Assessment of resting energy expenditure in pediatric mitochondrial diseases with indirect calorimetry

Mitochondrial diseases (MD) are the most frequent inborn errors of metabolism. In affected tissues, MD can alter cellular oxygen consumption rate leading to potential decreases in whole-body resting energy expenditure (REE), but data on pediatric children are absent. We determined, using indirect calorimetry (IC), whole-body oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and REE in pediatric patients with MD and healthy controls. Another goal was to assess the accuracy of available predictive equations for REE estimation in this patient population. IC data were obtained under fasting and resting conditions in 20 MD patients and 27 age and gender-matched healthy peers. We determined the agreement between REE measured with IC and REE estimated with Schofield weight and FAO/WHO/UNU equations. Mean values of VO2, VCO2 (mL·min-1·kg-1) or RQ did not differ significantly between patients and controls (P=0.085, P=0.055 and P=0.626 respectively). Accordingly, no significant differences (P=0.086) were found for REE (kcal·day-1kg-1) either. On the other hand, although we found no significant differences between IC-measured REE and Schofield or FAO/WHO/UNU-estimated REE, Bland-Altman analysis revealed wide limits of agreement and there were some important individual differences between IC and equation-derived REE. VO2, VCO2, RQ and REE are not significantly altered in pediatric patients with MD compared with healthy controls. The energy demands of pediatric patients with MD should be determined based on IC data in order to provide the best possible personalized nutritional management for these children.

Acidemia glutárica tipo 1: presentación de un caso y revisión de la literatura

Glutaric acidemia type I (GA-1) is a neurological disease of metabolic ethiology. Although considered rare, it is one of the most frequent inborn errors of metabolism in Colombia. GA-1 is caused by alterations in lysine, hydroxylysine and tryptophan metabolism, resulting in the accumulation of glutaric and 3-hydroxyglutaric acids in body fluids. Clinically, it is characterized by macrocephaly, progressive cerebral atrophy, and dystonia secondary to striatal degeneration. Due to its chronic evolution, it is usually under-diagnosed, so that several years may pass before suggestive symptoms or brain imaging findings are discovered. In some patients, the disease may appear acutely triggered by an infection between 6 and 18 months of age. Due to the availability of nutritional treatment, it is necessary to make an early diagnosis and to start treatment, in order to prevent or improve complications and associated diseases. It is important to consider GA-1 in the differential diagnosis of patients with spastic or dyskinetic cerebral palsy without a clear history of hypoxic events, as well as in patients with regression in neurological development. We report a case with acute presentation to exemplify the natural history of the disease and the diagnostic approach to it.

Pathophysiology of human mitochondrial diseases

Mitochondrial diseases, defined as the diseases due to oxidative phosphorylation defects, are the most frequent inborn errors of metabolism. Their clinical presentation is highly diverse. Their diagnosis is difficult. It relies on metabolic parameters, histological anomalies and enzymatic assays showing defective activity, all of which are both inconstant and relatively unspecific. Most mitochondrial diseases have a genetic origin. Candidate genes are very numerous, located either in the mitochondrial genome or the nuclear DNA. Pathophysiological mechanisms of mitochondrial diseases are still the matter of much debate. Those underlying the tissue-specificity of diseases due to the alterations of a ubiquitously expressed gene are discussed including (i) quantitative aspect of the expression of the causal gene or its partners when appropriate, (ii) quantitative aspects of the bioenergetic function in each tissue, and (iii) tissue distribution of heteroplasmic mitochondrial DNA alterations.

Co-administration of creatine plus pyruvate prevents the effects of phenylalanine administration to female rats during pregnancy and lactation on enzymes activity of energy metabolism in cerebral cortex and hippocampus of the offspring.

Phenylketonuria (PKU) is the most frequent inborn error of metabolism. It is caused by deficiency in the activity of phenylalanine hydroxylase, leading to accumulation of phenylalanine and its metabolites. Untreated maternal PKU or hyperphenylalaninemia may result in nonphenylketonuric offspring with low birth weight and neonatal sequelae, especially microcephaly and intellectual disability. The mechanisms underlying the neuropathology of brain injury in maternal PKU syndrome are poorly understood. In the present study, we evaluated the possible preventive effect of the co-administration of creatine plus pyruvate on the effects elicited by phenylalanine administration to female Wistar rats during pregnancy and lactation on some enzymes involved in the phosphoryltransfer network in the brain cortex and hippocampus of the offspring at 21days of age. Phenylalanine administration provoked diminution of body, brain cortex an hippocampus weight and decrease of adenylate kinase, mitochondrial and cytosolic creatine kinase activities. Co-administration of creatine plus pyruvate was effective in the prevention of those alterations provoked by phenylalanine, suggesting that altered energy metabolism may be important in the pathophysiology of maternal PKU. If these alterations also occur in maternal PKU, it is possible that pyruvate and creatine supplementation to the phenylalanine-restricted diet might be beneficial to phenylketonuric mothers.

Bulk autophagy, but not mitophagy, is increased in cellular model of mitochondrial disease

Oxidative phosphorylation system (OXPHOS) deficiencies are rare diseases but constitute the most frequent inborn errors of metabolism. We analyzed the autophagy route in 11 skin fibroblast cultures derived from patients with well characterized and distinct OXPHOS defects. Mitochondrial membrane potential determination revealed a tendency to decrease in 5 patients' cells but reached statistical significance only in 2 of them. The remaining cells showed either no change or a slight increase in this parameter. Colocalization analysis of mitochondria and autophagosomes failed to show evidence of increased selective elimination of mitochondria but revealed more intense autophagosome staining in patients' fibroblasts compared with controls. Despite the absence of increased mitophagy, Parkin recruitment to mitochondria was detected in both controls' and patients' cells and was slightly higher in cells harboring complex I defects. Western blot analysis of the autophagosome marker LC3B, confirmed significantly higher levels of the protein bound to autophagosomes, LC3B-II, in patients' cells, suggesting an increased bulk autophagy in OXPHOS defective fibroblasts. Inhibition of lysosomal proteases caused significant accumulation of LC3B-II in control cells, whereas in patients' cells this phenomenon was less pronounced. Electron microscopy studies showed higher content of late autophagic vacuoles and lysosomes in OXPHOS defective cells, accompanied by higher levels of the lysosomal marker LAMP-1. Our findings suggest that in OXPHOS deficient fibroblasts autophagic flux could be partially hampered leading to an accumulation of autophagic vacuoles and lysosomes.

Functional Studies of p.R132C, p.R149C, p.M283V, p.E431K, and a Novel c.652-2A&gt;G Mutations of the CYP21A2 Gene

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most frequent inborn error of metabolism and accounts for 90–95% of CAH cases. In the present work, we analyzed the functional consequence of four novel previously reported point CYP21A2 mutations -p.R132C, p.R149C, p.M283V, p.E431K- found in Argentinean 21-hydroxylase deficient patients. In addition, we report an acceptor splice site novel point mutation, c.652-2A>G, found in a classical patient in compound heterozygosity with the rare p.R483Q mutation. We performed bioinformatic and functional assays to evaluate the biological implication of the novel mutation. Our analyses revealed that the residual enzymatic activity of the isolated mutants coding for CYP21A2 aminoacidic substitutions was reduced to a lesser than 50% of the wild type with both progesterone and 17-OH progesterone as substrates. Accordingly, all the variants would predict mild non-classical alleles. In one non-classical patient, the p.E431K mutation was found in cis with the p.D322G one. The highest decrease in enzyme activity was obtained when both mutations were assayed in the same construction, with a residual activity most likely related to the simple virilizing form of the disease. For the c.652-2A>G mutation, bioinformatic tools predicted the putative use of two different cryptic splicing sites. Nevertheless, functional analyses revealed the use of only one cryptic splice acceptor site located within exon 6, leading to the appearance of an mRNA with a 16 nt deletion. A severe allele is strongly suggested due to the presence of a premature stop codon in the protein only 12 nt downstream.

Complicaciones anestésicas en pacientes con errores innatos del metabolismo sometidos a cirugía no cardiaca

IntroductionInborn errors of metabolism are alterations in one or more steps in a metabolic pathway. They are associated with multisystem complications and have a high impact on the quality of life of patients. Enzyme replacement has extended life, hence the importance of recognizing the most frequent anesthetic complications. ObjectiveTo describe the complications of anesthetic management in pediatric patients with inborn errors of metabolism undergoing non-cardiac surgery. MethodsRetrospective descriptive observational case series of pediatric patients with inborn errors of metabolism undergoing non-cardiac surgery at the Pablo Tobón Uribe Hospital between 2008 and 2011, and their anesthetic outcomes. ResultsThe most frequent inborn error of metabolism was glycogen storage disease type iii in 7 (37%), followed by nonketotic hyperglycinemia in 4 (21%). There were 2 (6%) anesthetic complications in the immediate post-operative period in patients with nonketotic hyper-glycinemia, with seizures in one case and the need for mechanical ventilation in another. ConclusionsLow-risk procedures probably explain why there were few complications. It was found that seizures and respiratory insufficiency are potential perioperative complications in nonketotic hyperglycinemia.

Anesthetic complications in patients with inborn errors of metabolism undergoing non-cardiac surgery

IntroductionInborn errors of metabolism are alterations in one or more steps in a metabolic pathway. They are associated with multisystem complications and have a high impact on the quality of life of patients. Enzyme replacement has extended life, hence the importance of recognizing the most frequent anesthetic complications. ObjectiveTo describe the complications of anesthetic management in pediatric patients with inborn errors of metabolism undergoing non-cardiac surgery. MethodsRetrospective descriptive observational case series of pediatric patients with inborn errors of metabolism undergoing non-cardiac surgery at the Pablo Tobón Uribe Hospital between 2008 and 2011, and their anesthetic outcomes. ResultsThe most frequent inborn error of metabolism was glycogen storage disease type III in 7 (37%), followed by nonketotic hyperglycinemia in 4 (21%). There were 2 (6%) anesthetic complications in the immediate post-operative period in patients with nonketotic hyperglycinemia, with seizures in one case and the need for mechanical ventilation in another. ConclusionsLow-risk procedures probably explain why there were few complications. It was found that seizures and respiratory insufficiency are potential perioperative complications in nonketotic hyperglycinemia.

Infantile Spasms (West Syndrome) in Children With Inborn Errors of Metabolism

West syndrome (infantile spasms) is an epileptic encephalopathy that includes psychomotor deterioration. In rare cases, it is due to an inherited, progressive metabolic disease. More than 25 inborn errors of metabolism have been considered etiologic or predisposing factors for infantile spasms. This is a review of the literature on reported cases of children diagnosed with a metabolic disease who developed infantile spasms. This article presents in brief the most frequent inborn errors of metabolism that have been associated with West syndrome and also illustrates the importance of screening for inborn errors of metabolism in infantile spasms.

The Live-Birth Prevalence of Mucopolysaccharidoses in Estonia

Previous studies on the prevalence of mucopolysaccharidoses (MPS) in different populations have shown considerable variations. There are, however, few data with regard to the prevalence of MPSs in Fenno-Ugric populations or in north-eastern Europe, except for a report about Scandinavian countries. A retrospective epidemiological study of MPSs in Estonia was undertaken, and live-birth prevalence of MPS patients born between 1985 and 2006 was estimated. The live-birth prevalence for all MPS subtypes was found to be 4.05 per 100,000 live births, which is consistent with most other European studies. MPS II had the highest calculated incidence, with 2.16 per 100,000 live births (4.2 per 100,000 male live births), forming 53% of all diagnosed MPS cases, and was twice as high as in other studied European populations. The second most common subtype was MPS IIIA, with a live-birth prevalence of 1.62 in 100,000 live births. With 0.27 out of 100,000 live births, MPS VI had the third-highest live-birth prevalence. No cases of MPS I were diagnosed in Estonia, making the prevalence of MPS I in Estonia much lower than in other European populations. MPSs are the third most frequent inborn error of metabolism in Estonia after phenylketonuria and galactosemia.