Genomic analyses in Cornelia de Lange Syndrome and related diagnoses: Novel candidate genes, genotype-phenotype correlations and common mechanisms.

Cornelia de Lange Syndrome (CdLS) is a rare, dominantly inherited multisystem developmental disorder characterized by highly variable manifestations of growth and developmental delays, upper limb involvement, hypertrichosis, cardiac, gastrointestinal, craniofacial, and other systemic features. Pathogenic variants in genes encoding cohesin complex structural subunits and regulatory proteins (NIPBL, SMC1A, SMC3, HDAC8, and RAD21) are the major pathogenic contributors to CdLS. Heterozygous or hemizygous variants in the genes encoding these five proteins have been found to be contributory to CdLS, with variants in NIPBL accounting for the majority (>60%) of cases, and the only gene identified to date that results in the severe or classic form of CdLS when mutated. Pathogenic variants in cohesin genes other than NIPBL tend to result in a less severe phenotype. Causative variants in additional genes, such as ANKRD11, EP300, AFF4, TAF1, and BRD4, can cause a CdLS-like phenotype. The common role that these genes, and others, play as critical regulators of developmental transcriptional control has led to the conditions they cause being referred to as disorders of transcriptional regulation (or "DTRs"). Here, we report the results of a comprehensive molecular analysis in a cohort of 716 probands with typical and atypical CdLS in order to delineate the genetic contribution of causative variants in cohesin complex genes as well as novel candidate genes, genotype-phenotype correlations, and the utility of genome sequencing in understanding the mutational landscape in this population.

Linked-read genome sequencing identifies biallelic pathogenic variants in DONSON as a novel cause of Meier-Gorlin syndrome.

MATERIAL: Linked-read whole genome sequencing (WGS) presents a new opportunity for cost-efficient singleton sequencing in place of traditional trio-based designs while generating informative-phased variants, effective for recessive disorders when parental DNA is unavailable. METHODS: We have applied linked-read WGS to identify novel causes of Meier-Gorlin syndrome (MGORS), a condition recognised by short stature, microtia and patella hypo/aplasia. There are eight genes associated with MGORS to date, all encoding essential components involved in establishing and initiating DNA replication. RESULTS: Our successful phasing of linked-read data led to the identification of biallelic rare variants in four individuals (24% of our cohort) in DONSON, a recently established DNA replication fork surveillance factor. The variants include five novel missense and one deep intronic variant. All were demonstrated to be deleterious to function; the missense variants all disrupted the nuclear localisation of DONSON, while the intronic variant created a novel splice site that generated an out-of-frame transcript with no residual canonical transcript produced. CONCLUSION: Variants in DONSON have previously been associated with extreme microcephaly, short stature and limb anomalies and perinatal lethal microcephaly-micromelia syndrome. Our novel genetic findings extend the complicated spectrum of phenotypes associated with DONSON variants and promote novel hypotheses for the role of DONSON in DNA replication. While our findings reiterate that MGORS is a disorder of DNA replication, the pathophysiology is obviously complex. This successful identification of a novel disease gene for MGORS highlights the utility of linked-read WGS as a successful technology to be considered in the genetic studies of recessive conditions.

Phenotypic variability in deficiency of the α subunit of succinate-CoA ligase.

Succinyl-CoA synthetase or succinate-CoA ligase deficiency can result from biallelic mutations in SUCLG1 gene that encodes for the alpha subunit of the succinyl-CoA synthetase. Mutations in this gene were initially associated with fatal infantile lactic acidosis. We describe an individual with a novel biallelic pathogenic mutation in SUCLG1 with a less severe phenotype dominated by behavioral problems. The mutation was identified to be c.512A>G corresponding to a p.Asn171Ser change in the protein. The liquid chromatography tandem mass spectrometry-based enzyme activity assay on cultured fibroblasts revealed a markedly reduced activity of succinyl-CoA synthetase enzyme when both ATP and GTP were substrates, affecting both ADP-forming and GDP-forming functions of the enzyme.

Diagnosis and management of glycogen storage diseases type VI and IX: a clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).

PURPOSE: Glycogen storage disease (GSD) types VI and IX are rare diseases of variable clinical severity affecting primarily the liver. GSD VI is caused by deficient activity of hepatic glycogen phosphorylase, an enzyme encoded by the PYGL gene. GSD IX is caused by deficient activity of phosphorylase kinase (PhK), the enzyme subunits of which are encoded by various genes: ɑ (PHKA1, PHKA2), ß (PHKB), É£ (PHKG1, PHKG2), and δ (CALM1, CALM2, CALM3). Glycogen storage disease types VI and IX have a wide spectrum of clinical manifestations and often cannot be distinguished from each other, or from other liver GSDs, on clinical presentation alone. Individuals with GSDs VI and IX can present with hepatomegaly with elevated serum transaminases, ketotic hypoglycemia, hyperlipidemia, and poor growth. This guideline for the management of GSDs VI and IX was developed as an educational resource for health-care providers to facilitate prompt and accurate diagnosis and appropriate management of patients. METHODS: A national group of experts in various aspects of GSDs VI and IX met to review the limited evidence base from the scientific literature and provided their expert opinions. Consensus was developed in each area of diagnosis, treatment, and management. Evidence bases for these rare disorders are largely based on expert opinion, particularly when targeted therapeutics that have to clear the US Food and Drug Administration (FDA) remain unavailable. RESULTS: This management guideline specifically addresses evaluation and diagnosis across multiple organ systems involved in GSDs VI and IX. Conditions to consider in a differential diagnosis stemming from presenting features and diagnostic algorithms are discussed. Aspects of diagnostic evaluation and nutritional and medical management, including care coordination, genetic counseling, and prenatal diagnosis are addressed. CONCLUSION: A guideline that will facilitate the accurate diagnosis and optimal management of patients with GSDs VI and IX was developed. This guideline will help health-care providers recognize patients with GSDs VI and IX, expedite diagnosis, and minimize adverse sequelae from delayed diagnosis and inappropriate management. It will also help identify gaps in scientific knowledge that exist today and suggest future studies.

Airway-related symptoms and surgeries in patients with mucopolysaccharidosis I.

OBJECTIVE: Mucopolysaccharidosis I (MPS I) is a progressive, debilitating, and life-threatening genetic disease, which, owing to the nonspecific nature of the early symptoms, is often unrecognized and associated with significant diagnostic delays. To improve early recognition leading to early diagnosis and initiation of treatment, we characterized the extent of airway-related symptoms and surgeries among patients with MPS I. METHODS: Analysis of the frequency of airway-related symptoms and surgeries from 1041 patients enrolled in the MPS I Registry and correlation with other systemic manifestations of MPS I. RESULTS: Airway-related symptoms (macroglossia, enlarged tonsils, reactive airway disease/asthma, or sleep disturbances) were reported for as many as 85% of Hurler, 83% of Hurler-Scheie, and 65% of Scheie patients-very often before the diagnosis of MPS I was established. Surgeries for an airway indication were reported in 39% of patients and many had at least 1 airway-related surgery before the diagnosis of MPS I was confirmed. The mean percentage of patients with airway-related symptoms for whom hernias and/or dysostosis multiplex were also reported was 84% and 54%, respectively. CONCLUSION: Airway-related symptoms and surgeries are common and often the earliest presenting feature in MPS I. Improved recognition of early MPS I disease manifestations may lead to earlier diagnosis and treatment.

Diagnosis and management of glycogen storage disease type I: a practice guideline of the American College of Medical Genetics and Genomics.

PURPOSE: Glycogen storage disease type I (GSD I) is a rare disease of variable clinical severity that primarily affects the liver and kidney. It is caused by deficient activity of the glucose 6-phosphatase enzyme (GSD Ia) or a deficiency in the microsomal transport proteins for glucose 6-phosphate (GSD Ib), resulting in excessive accumulation of glycogen and fat in the liver, kidney, and intestinal mucosa. Patients with GSD I have a wide spectrum of clinical manifestations, including hepatomegaly, hypoglycemia, lactic acidemia, hyperlipidemia, hyperuricemia, and growth retardation. Individuals with GSD type Ia typically have symptoms related to hypoglycemia in infancy when the interval between feedings is extended to 3­4 hours. Other manifestations of the disease vary in age of onset, rate of disease progression, and severity. In addition, patients with type Ib have neutropenia, impaired neutrophil function, and inflammatory bowel disease. This guideline for the management of GSD I was developed as an educational resource for health-care providers to facilitate prompt, accurate diagnosis and appropriate management of patients. METHODS: A national group of experts in various aspects of GSD I met to review the evidence base from the scientific literature and provided their expert opinions. Consensus was developed in each area of diagnosis, treatment, and management. RESULTS: This management guideline specifically addresses evaluation and diagnosis across multiple organ systems (hepatic, kidney, gastrointestinal/nutrition, hematologic, cardiovascular, reproductive) involved in GSD I. Conditions to consider in the differential diagnosis stemming from presenting features and diagnostic algorithms are discussed. Aspects of diagnostic evaluation and nutritional and medical management, including care coordination, genetic counseling, hepatic and renal transplantation, and prenatal diagnosis, are also addressed. CONCLUSION: A guideline that facilitates accurate diagnosis and optimal management of patients with GSD I was developed. This guideline helps health-care providers recognize patients with all forms of GSD I, expedite diagnosis, and minimize adverse sequelae from delayed diagnosis and inappropriate management. It also helps to identify gaps in scientific knowledge that exist today and suggests future studies.

Recessive mutations in PCBD1 cause a new type of early-onset diabetes.

Mutations in several genes cause nonautoimmune diabetes, but numerous patients still have unclear genetic defects, hampering our understanding of the development of the disease and preventing pathogenesis-oriented treatment. We used whole-genome sequencing with linkage analysis to study a consanguineous family with early-onset antibody-negative diabetes and identified a novel deletion in PCBD1 (pterin-4 α-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor 1 α), a gene that was recently proposed as a likely cause of diabetes. A subsequent reevaluation of patients with mild neonatal hyperphenylalaninemia due to mutations in PCBD1 from the BIODEF database identified three additional patients who had developed HNF1A-like diabetes in puberty, indicating early ß-cell failure. We found that Pcbd1 is expressed in the developing pancreas of both mouse and Xenopus embryos from early specification onward showing colocalization with insulin. Importantly, a morpholino-mediated knockdown in Xenopus revealed that pcbd1 activity is required for the proper establishment of early pancreatic fate within the endoderm. We provide the first genetic evidence that PCBD1 mutations can cause early-onset nonautoimmune diabetes with features similar to dominantly inherited HNF1A-diabetes. This condition responds to and can be treated with oral drugs instead of insulin, which is important clinical information for these patients. Finally, patients at risk can be detected through a newborn screening for phenylketonuria.

The natural history of MPS I: global perspectives from the MPS I Registry.

PURPOSE: In this study, we aimed to describe the natural history of mucopolysaccharidosis I. METHODS: Data from 1,046 patients who enrolled in the MPS I Registry as of August 2013 were available for descriptive analysis. Only data from untreated patients and data prior to treatment for patients who received treatment were considered. Age at symptom onset, diagnosis, and treatment initiation were examined by geographic region and phenotype (from most to least severe: Hurler, Hurler-Scheie, and Scheie). For each symptom, frequency and age at onset were examined. RESULTS: Natural history data were available for 987 patients. Most patients were from Europe (45.5%), followed by North America (34.8%), Latin America (17.3%), and Asia Pacific (2.4%). Phenotype distribution was 60.9% for Hurler, 23.0% for Hurler-Scheie, and 12.9% for Scheie (3.2% undetermined) syndromes. Median age at symptom onset for Hurler, Hurler-Scheie, and Scheie syndromes was 6 months, 1.5 years, and 5.3 years, respectively; median age at treatment initiation was 1.5 years, 8.0 years, and 16.9 years, respectively. Coarse facial features and corneal clouding were among the most common symptoms in all three phenotypes. CONCLUSION: A delay between symptom onset and treatment exists, especially in patients with attenuated mucopolysaccharidosis I. A better understanding of disease manifestations may help facilitate prompt diagnosis and treatment and improve patient outcomes.

Mutations in the TGF-ß repressor SKI cause Shprintzen-Goldberg syndrome with aortic aneurysm.

Elevated transforming growth factor (TGF)-ß signaling has been implicated in the pathogenesis of syndromic presentations of aortic aneurysm, including Marfan syndrome (MFS) and Loeys-Dietz syndrome (LDS). However, the location and character of many of the causal mutations in LDS intuitively imply diminished TGF-ß signaling. Taken together, these data have engendered controversy regarding the specific role of TGF-ß in disease pathogenesis. Shprintzen-Goldberg syndrome (SGS) has considerable phenotypic overlap with MFS and LDS, including aortic aneurysm. We identified causative variation in ten individuals with SGS in the proto-oncogene SKI, a known repressor of TGF-ß activity. Cultured dermal fibroblasts from affected individuals showed enhanced activation of TGF-ß signaling cascades and higher expression of TGF-ß-responsive genes relative to control cells. Morpholino-induced silencing of SKI paralogs in zebrafish recapitulated abnormalities seen in humans with SGS. These data support the conclusions that increased TGF-ß signaling is the mechanism underlying SGS and that high signaling contributes to multiple syndromic presentations of aortic aneurysm.

High rate of postoperative mortality in patients with mucopolysaccharidosis I: findings from the MPS I Registry.

BACKGROUND/PURPOSE: Mucopolysaccharidosis I (MPS I) is a rare lysosomal storage disorder caused by deficiency of α-L-iduronidase, which results in progressive multisystemic disease. Patients with MPS I often require multiple common and uncommon surgeries and are at risk for surgical and anesthetic complications because of respiratory and cardiac disease. Surgery often precedes diagnosis; thus, surgeons and anesthesiologists may be unaware of potential risks. METHODS: We analyzed data from the MPS I Registry, a voluntary observational database, for deaths occurring within 1 month of a surgical procedure among the 932 patients enrolled as of July 2010. RESULTS: Among the 196 deceased patients, 186 reported 1 surgery or more, and 32 had 1 surgery or more within 1 month of death, including 20 who had 1 surgery or more within 10 days of death. Surgeries before death included hernia repair, central line placement, spinal surgery, tracheostomy, and ventriculo-peritoneal shunt. Most patients (28/32) had severe MPS I (Hurler), and 20 of 32 patients (all Hurler) died at 3 years or younger. In 6 of 32 patients, surgery was directly noted in the cause of death, including 4 patients with an attenuated form of MPS I. CONCLUSIONS: Patients with mucopolysaccharidosis have a high postoperative mortality because of underlying respiratory and cardiac diseases.

Diagnosis and treatment trends in mucopolysaccharidosis I: findings from the MPS I Registry.

UNLABELLED: Our objective was to assess how the diagnosis and treatment of mucopolysaccharidosis I (MPS I) have changed over time. We used data from 891 patients in the MPS I Registry, an international observational database, to analyze ages at symptom onset, diagnosis, treatment initiation, and treatment allocation (hematopoietic stem cell transplantation, enzyme replacement therapy with laronidase, both, or neither) over time for all disease phenotypes (Hurler, Hurler-Scheie, and Scheie syndromes). The interval between diagnosis and treatment has become shorter since laronidase became available in 2003 (gap during 2006-2009: Hurler--0.2 year, Hurler-Scheie--0.5 year, Scheie--1.4 years). However, the age at diagnosis has not decreased for any MPS I phenotype over time, and the interval between symptom onset and treatment initiation remains substantial for both Hurler-Scheie and Scheie patients (gap during 2006-2009, 2.42 and 6.71 years, respectively). Among transplanted patients, an increasing proportion received hematopoietic stem cells from cord blood (34 out of 64 patients by 2009) and was also treated with laronidase (42 out of 45 patients by 2009). CONCLUSIONS: Despite the availability of laronidase since 2003, the diagnosis of MPS I is still substantially delayed for patients with Hurler-Scheie and Scheie phenotypes, which can lead to a sub-optimal treatment outcome. Increased awareness of MPS I signs and symptoms by primary care providers and pediatric subspecialists is crucial to initiate early treatment and to improve the quality of life of MPS I patients.

Glycogen storage disease type III diagnosis and management guidelines.

PURPOSE: Glycogen storage disease type III is a rare disease of variable clinical severity affecting primarily the liver, heart, and skeletal muscle. It is caused by deficient activity of glycogen debranching enzyme, which is a key enzyme in glycogen degradation. Glycogen storage disease type III manifests a wide clinical spectrum. Individuals with glycogen storage disease type III present with hepatomegaly, hypoglycemia, hyperlipidemia, and growth retardation. Those with type IIIa have symptoms related to liver disease and progressive muscle (cardiac and skeletal) involvement that varies in age of onset, rate of disease progression, and severity. Those with type IIIb primarily have symptoms related to liver disease. This guideline for the management of glycogen storage disease type III was developed as an educational resource for health care providers to facilitate prompt and accurate diagnosis and appropriate management of patients. METHODS: An international group of experts in various aspects of glycogen storage disease type III met to review the evidence base from the scientific literature and provided their expert opinions. Consensus was developed in each area of diagnosis, treatment, and management. RESULTS: This management guideline specifically addresses evaluation and diagnosis across multiple organ systems (cardiovascular, gastrointestinal/nutrition, hepatic, musculoskeletal, and neuromuscular) involved in glycogen storage disease type III. Conditions to consider in a differential diagnosis stemming from presenting features and diagnostic algorithms are discussed. Aspects of diagnostic evaluation and nutritional and medical management, including care coordination, genetic counseling, hepatic transplantation, and prenatal diagnosis, are addressed. CONCLUSIONS: A guideline that will facilitate the accurate diagnosis and appropriate management of individuals with glycogen storage disease type III was developed. This guideline will help health care providers recognize patients with all forms of glycogen storage disease type III, expedite diagnosis, and minimize stress and negative sequelae from delayed diagnosis and inappropriate management. It will also help identify gaps in scientific knowledge that exist today and suggest future studies.

Clinical and mutational spectrum of neurofibromatosis type 1-like syndrome.

CONTEXT: Autosomal dominant inactivating sprouty-related EVH1 domain-containing protein 1 (SPRED1) mutations have recently been described in individuals presenting mainly with café au lait macules (CALMs), axillary freckling, and macrocephaly. The extent of the clinical spectrum of this new disorder needs further delineation. OBJECTIVE: To determine the frequency, mutational spectrum, and phenotype of neurofibromatosis type 1-like syndrome (NFLS) in a large cohort of patients. DESIGN, SETTING, AND PARTICIPANTS: In a cross-sectional study, 23 unrelated probands carrying a SPRED1 mutation identified through clinical testing participated with their families in a genotype-phenotype study (2007-2008). In a second cross-sectional study, 1318 unrelated anonymous samples collected in 2003-2007 from patients with a broad range of signs typically found in neurofibromatosis type 1 (NF1) but no detectable NF1 germline mutation underwent SPRED1 mutation analysis. MAIN OUTCOME MEASURES: Comparison of aggregated clinical features in patients with or without a SPRED1 or NF1 mutation. Functional assays were used to evaluate the pathogenicity of missense mutations. RESULTS: Among 42 SPRED1-positive individuals from the clinical cohort, 20 (48%; 95% confidence interval [CI], 32%-64%) fulfilled National Institutes of Health (NIH) NF1 diagnostic criteria based on the presence of more than 5 CALMs with or without freckling or an NF1-compatible family history. None of the 42 SPRED1-positive individuals (0%; 95% CI, 0%-7%) had discrete cutaneous or plexiform neurofibromas, typical NF1 osseous lesions, or symptomatic optic pathway gliomas. In the anonymous cohort of 1318 individuals, 34 different SPRED1 mutations in 43 probands were identified: 27 pathogenic mutations in 34 probands and 7 probable nonpathogenic missense mutations in 9 probands. Of 94 probands with familial CALMs with or without freckling and no other NF1 features, 69 (73%; 95% CI, 63%-80%) had an NF1 mutation and 18 (19%; 95% CI, 12%-29%) had a pathogenic SPRED1 mutation. In the anonymous cohort, 1.9% (95% CI, 1.2%-2.9%) of individuals with the clinical diagnosis of NF1 according to the NIH criteria had NFLS. CONCLUSIONS: A high SPRED1 mutation detection rate was found in NF1 mutation-negative families with an autosomal dominant phenotype of CALMs with or without freckling and no other NF1 features. Among individuals in this study, NFLS was not associated with the peripheral and central nervous system tumors seen in NF1.

Education format and resource preferences among registrants of a pediatric-focused CME website.

BACKGROUND: Despite dramatic increase in Internet-based CME activities, little is known about physician Internet CME preferences. AIMS: To identify the education format and resource preferences among registrants of a pediatric-focused CME website. METHODS: Preferences of physician registrants at PedsEducation.org between July 2000-November 2007 (n = 1388) were assessed via survey. A secondary analysis of respondent demographics vs. reported preferences was conducted. RESULTS: A total of 345 physicians participated (25% response rate). The majority (73%, n = 252) identified free CME as a highly important feature of an Internet CME resource; monthly case series was identified as the least important. Seventy-five percent of respondents (n = 260) identified practice guideline updates as a highly useful practice resource; practice feedback was identified as the least useful. Respondents with < or =10 years practice experience were more likely to identify case-based CME as highly useful to their daily practice (p < 0.001); respondents who spend > or = 90% working time on patient care were more likely to identify Internet CME as a highly useful CME format (p < 0.001). CONCLUSION: Internet CME preferences of PedsEducation.org registrants differ from those typically associated with knowledge gains and behavior changes. Demographic characteristics may influence these preferences.

Characterization of surgical procedures in patients with mucopolysaccharidosis type I: findings from the MPS I Registry.

OBJECTIVE: To clarify the extent and chronology of surgical burden in relation to symptom onset and diagnosis in patients with mucopolysaccharidosis I (MPS I) as reported in the MPS I Registry, an international observational database. STUDY DESIGN: Analysis of surgical data from 544 patients enrolled in the MPS I Registry. Among all patients with at least 1 reported surgery, the number and frequency of procedures, and age at procedure, diagnosis, and symptom onset were collected overall, by patient, and by reported phenotype (Hurler, Hurler-Scheie, Scheie). RESULTS: Overall and by phenotype, approximately 75% of patients in the MPS I Registry reported at least 1 surgery. The most common were myringotomies and related procedures, hernia repair, adenoidectomy/tonsillectomy, and carpal-tunnel release. Median age at first surgery was <5 years. A median of 3 to 4 surgeries was reported per patient. By age 1.5, 4, and 10 years, respectively, 22%, 44%, and 54% of patients reported > or = 2 surgeries. At least 1 surgery preceded diagnosis in 36%, 46%, and 63% of patients with Hurler, Hurler-Scheie, and Scheie, respectively. CONCLUSIONS: Pediatricians and pediatric surgeons need to be aware of the surgical burden of MPS I and be alert to its presenting signs and symptoms in children scheduled for surgery.

Newborn screening: current status.

Newborn screening, which represents one of the major advances in child health of the past century, has been carried out in all fifty U.S. states since the 1970s. Newborn screening programs are state-run, and decisions are left to the individual states regarding the conditions to be screened for, the mechanism for confirmatory testing, follow-up care, and financing of the programs. Laboratory advances in tandem mass spectrometry make it possible to screen newborns for many rare inborn errors of metabolism. This raises many policy issues including screening's cost-effectiveness, ethics, quality, and oversight.

The MPS I registry: design, methodology, and early findings of a global disease registry for monitoring patients with Mucopolysaccharidosis Type I.

A global, observational disease registry has been established to characterize the course of disease and track clinical outcomes in patients with Mucopolysaccharidosis Type I (MPS I), a rare and treatable lysosomal storage disorder. This report outlines procedures for data collection and presents the recommended minimum schedule of assessments that comprise the disease-specific clinical and laboratory parameters that are tracked in the database. Aggregate data are summarized for the first 302 patients enrolled, representing entries from 24 countries. The median current age of the patients is 9.0 years (range: 0.4-64.8). Syndrome diagnoses include 47% Hurler (severe form), 25% Hurler-Scheie (attenuated form with an intermediate phenotype), 13% Scheie (most attenuated form), and 15% unknown. Younger ages at symptom onset and disease diagnosis are associated with the severe Hurler syndrome, but there is overlap among syndromes. Diagnosis was delayed by years to decades in several patients with Hurler-Scheie and Scheie syndromes. Patients with symptom onset before age 5 are more likely to have a gibbus, cognitive impairment, and pneumonia, whereas patients with symptom onset above age 5 are more likely to have carpal tunnel syndrome, myelopathy, and glaucoma. Cardiac valve abnormalities, joint contractures, corneal clouding, and hernia are reported by over 70% of patients regardless of the age of symptom onset. Approximately 80% of the patients have received enzyme replacement therapy, hematopoietic stem cell transplantation, or both. Overall, the MPS I Registry database contains a broad sample of the global patient population, providing a potentially useful tool for expanding knowledge of MPS I and facilitating evidence-based decisions about the optimal means of monitoring and treating affected individuals.