Efficacy and safety of enzyme replacement therapy with alglucosidase alfa for the treatment of patients with infantile-onset Pompe disease: a systematic review and metanalysis.

Introduction: Pompe disease (PD) is a glycogen disorder caused by the deficient activity of acid alpha-glucosidase (GAA). We sought to review the latest available evidence on the safety and efficacy of recombinant human GAA enzyme replacement therapy (ERT) for infantile-onset PD (IOPD). Methods: We systematically searched the MEDLINE (via PubMed) and Embase databases for prospective clinical studies evaluating ERT for IOPD on pre-specified outcomes. Meta-analysis was also performed. Results: Of 1,722 articles identified, 16 were included, evaluating 316 patients. Studies were heterogeneous and with very low certainty of evidence for most outcomes. A moderate/high risk of bias was present for most included articles. The following outcomes showed improvements associated with alglucosidase alfa, over natural history of PD/placebo, for a mean follow-up of 48.3 months: left ventricular (LV) mass {mean change 131.3 g/m2 [95% confidence interval (CI) 81.02, 181.59]}, time to start ventilation (TSV) [HR 0.21 (95% CI: 0.12, 0.36)], and survival [HR 0.10 (95% CI: 0.05, 0.19)]. There were no differences between the pre- and post-ERT period for myocardial function and psychomotor development. Adverse events (AEs) after ERT were mild in most cases. Conclusion: Our data suggest that alglucosidase alfa potentially improves LV mass, TSV, and survival in IOPD patients, with no important safety issues. Systematic Review Registration: PROSPERO identifier (CRD42019123700).

Burden of phenylketonuria in Latin American patients: a systematic review and meta-analysis of observational studies.

BACKGROUND: Phenylketonuria (PKU) is an inborn error of metabolism caused by a deficiency of the enzyme phenylalanine hydroxylase. If untreated, the complications of PKU lead to significant neucognitive and neuropsychiatric impairments, placing a burden on both the individual's quality of life and on the healthcare system. We conducted a systematic literature review to characterize the impact of PKU on affected individuals and on healthcare resources in Latin American (LATAM) countries. METHODS: Searches of the global medical literature as well as regional and local medical literature up to September 2021. Observational studies on patients with PKU from any LATAM country. Pairs of reviewers independently screened eligible articles, extracted data from included studies, and assessed their risk of bias. RESULTS: 79 unique studies (47 cross-sectional studies, 18 case series, 12 case reports, and two cohort studies) with a total of 4090 patients were eligible. Of these studies, 20 had data available evaluating early-diagnosed PKU patients for meta-analysis of burden outcomes. Intellectual disability in the pooled studies was 18% [95% Confidence Interval (CI) 0.04-0.38; I2 = 83.7%, p = 0.0133; two studies; n = 114]. Motor delay was 15% [95% CI 0.04-0.30; I2 = 74.5%, p = 0.0083; four studies; n = 132]. Speech deficit was 35% [95% CI 0.08-0.68; I2 = 93.9%, p < 0.0001; five studies; n = 162]. CONCLUSIONS: There is currently evidence of high clinical burden in PKU patients in LATAM countries. Recognition that there are many unmet neuropsychological needs and socioeconomic challenges faced in the LATAM countries is the first step in planning cost-effective interventions.

Infant mortality in Brazil attributable to inborn errors of metabolism associated with sudden death: a time-series study (2002-2014).

BACKGROUND: The literature suggests that 0.9 to 6% of infants who die unexpectedly may have had a metabolic disorder. At least 43 different inborn errors of metabolism (IEMs) have been associated with sudden death (SUDI). To date, the frequency of IEM-associated SUDI has not been studied in Brazil. The present study sought to characterize infant mortality related to IEMs known to cause SUDI disaggregated by each of the regions of Brazil. METHODS: This was a descriptive, cross-sectional, population-based study of data obtained from the Brazilian Ministry of Health Mortality Information System (SIM). Death records were obtained for all infants (age < 1 year) who died in Brazil in 2002-2014 in whom the underlying cause of death was listed as ICD-10 codes E70 (Disorders of aromatic amino-acid metabolism), E71 (Disorders of branched-chain amino-acid metabolism and fatty-acid metabolism), E72 (Other disorders of amino-acid metabolism), or E74 (Other disorders of carbohydrate metabolism), which are known to be associated with SUDI. RESULTS: From 2002 to 2014, 199 deaths of infants aged < 1 year were recorded in the SIM with an underlying cause corresponding to one of the IEMs of interest. The prevalence of IEM-related deaths was 0.67 per 10,000 live births (0.58-0.77). Of these 199 deaths, 18 (9.0%) occurred in the North of Brazil, 43 (21.6%) in the Northeast, 80 (40.2%) in the Southeast, 46 (23.1%) in the South, and 12 (6.0%) in the Center-West region. Across all regions of the country, ICD10-E74 was predominant. CONCLUSIONS: This 13-year time-series study provides the first analysis of the number of infant deaths in Brazil attributable to IEMs known to be associated with sudden death.

Universal newborn screening: A roadmap for action.

Newborn screening (NBS) prevents morbidity and mortality by screening babies for selected disorders in the first days of life so that early diagnosis and treatment can be initiated. Congenital disorders impact an estimated 8 million or 6% of annual births worldwide, and of the top five that contribute 25% to the global burden of these disorders, three can be identified and managed by NBS. There are determined pockets of activity in Latin America, Sub-Saharan Africa, and the Asia Pacific region, where partnerships among government, non-governmental organizations, academia, the private sector and civil society are developing novel NBS programs that are both saving lives and preventing disability in those who survive.

Quality of life and adherence to treatment in early-treated Brazilian phenylketonuria pediatric patients

Early dietary treatment of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, results in normal cognitive development. Although health-related quality of life (HRQoL) of PKU patients has been reported as unaffected in high-income countries, there are scarce data concerning HRQoL and adherence to treatment of PKU children and adolescents from Brazil. The present study compared HRQoL scores in core dimensions of Brazilian early-treated PKU pediatric patients with those of a reference population, and explored possible relationships between adherence to treatment and HRQoL. Early-treated PKU pediatric patient HRQoL was evaluated by self- and parent-proxy reports of the Pediatric Quality of Life Inventory (PedsQL) core scales. Adherence to treatment was evaluated by median Phe levels and percentage of results within the therapeutic target range in two periods. Means for total and core scales scores of PedsQL self- and parent proxy-reports of PKU patients were significantly lower than their respective means for controls. Adequacy of median Phe concentrations and the mean percentage of values in the target range fell substantially from the first year of life to the last year of this study. There was no significant difference in mean total and core scale scores for self- and parent proxy-reports between patients with adequate and those with inadequate median Phe concentrations. The harmful consequences for intellectual capacity caused by poor adherence to dietary treatment could explain the observed decrease in all HRQoL scales, especially in school functioning. Healthcare system and financial difficulties may also have influenced negatively all HRQoL dimensions.

Quality of life and adherence to treatment in early-treated Brazilian phenylketonuria pediatric patients.

Early dietary treatment of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, results in normal cognitive development. Although health-related quality of life (HRQoL) of PKU patients has been reported as unaffected in high-income countries, there are scarce data concerning HRQoL and adherence to treatment of PKU children and adolescents from Brazil. The present study compared HRQoL scores in core dimensions of Brazilian early-treated PKU pediatric patients with those of a reference population, and explored possible relationships between adherence to treatment and HRQoL. Early-treated PKU pediatric patient HRQoL was evaluated by self- and parent-proxy reports of the Pediatric Quality of Life Inventory (PedsQL) core scales. Adherence to treatment was evaluated by median Phe levels and percentage of results within the therapeutic target range in two periods. Means for total and core scales scores of PedsQL self- and parent proxy-reports of PKU patients were significantly lower than their respective means for controls. Adequacy of median Phe concentrations and the mean percentage of values in the target range fell substantially from the first year of life to the last year of this study. There was no significant difference in mean total and core scale scores for self- and parent proxy-reports between patients with adequate and those with inadequate median Phe concentrations. The harmful consequences for intellectual capacity caused by poor adherence to dietary treatment could explain the observed decrease in all HRQoL scales, especially in school functioning. Healthcare system and financial difficulties may also have influenced negatively all HRQoL dimensions.

Exome sequencing for mucolipidosis III: Detection of a novel GNPTAB gene mutation in a patient with a very mild phenotype.

Mucolipidosis II and III alpha/beta (ML II/III alpha/beta) are rare autosomal recessive lysosomal storage diseases that are caused by a deficiency of UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the enzyme responsible for the synthesis of the mannose 6-phosphate targeting signal on lysosomal hydrolases. A Brazilian patient suspected of having a very mild ML III was investigated using whole next-generation sequencing (NGS). Two mutations in the GNPTAB gene were detected and confirmed to be in trans status by parental analysis: c.1208T>C (p.Ile403Thr), previously reported as being pathogenic, and the novel mutation c.1723G>A (p.Gly575Arg). This study demonstrates the effectiveness of using whole NGS for the molecular diagnosis of very mild ML III alpha/beta patients.

Successful domino liver transplantation in maple syrup urine disease using a related living donor

Maple syrup urine disease (MSUD) is an autosomal recessive disease associated with high levels of branched-chain amino acids. Children with MSUD can present severe neurological damage, but liver transplantation (LT) allows the patient to resume a normal diet and avoid further neurological damage. The use of living related donors has been controversial because parents are obligatory heterozygotes. We report a case of a 2-year-old child with MSUD who underwent a living donor LT. The donor was the patient's mother, and his liver was then used as a domino graft. The postoperative course was uneventful in all three subjects. DNA analysis performed after the transplantation (sequencing of the coding regions of BCKDHA, BCKDHB, and DBT genes) showed that the MSUD patient was heterozygous for a pathogenic mutation in the BCKDHB gene. This mutation was not found in his mother, who is an obligatory carrier for MSUD according to the family history and, as expected, presented both normal clinical phenotype and levels of branched-chain amino acids. In conclusion, our data suggest that the use of a related donor in LT for MSUD was effective, and the liver of the MSUD patient was successfully used in domino transplantation. Routine donor genotyping may not be feasible, because the test is not widely available, and, most importantly, the disease is associated with both the presence of allelic and locus heterogeneity. Further studies with this population of patients are required to expand the use of related donors in MSUD.

Successful domino liver transplantation in maple syrup urine disease using a related living donor.

Maple syrup urine disease (MSUD) is an autosomal recessive disease associated with high levels of branched-chain amino acids. Children with MSUD can present severe neurological damage, but liver transplantation (LT) allows the patient to resume a normal diet and avoid further neurological damage. The use of living related donors has been controversial because parents are obligatory heterozygotes. We report a case of a 2-year-old child with MSUD who underwent a living donor LT. The donor was the patient's mother, and his liver was then used as a domino graft. The postoperative course was uneventful in all three subjects. DNA analysis performed after the transplantation (sequencing of the coding regions of BCKDHA, BCKDHB, and DBT genes) showed that the MSUD patient was heterozygous for a pathogenic mutation in the BCKDHB gene. This mutation was not found in his mother, who is an obligatory carrier for MSUD according to the family history and, as expected, presented both normal clinical phenotype and levels of branched-chain amino acids. In conclusion, our data suggest that the use of a related donor in LT for MSUD was effective, and the liver of the MSUD patient was successfully used in domino transplantation. Routine donor genotyping may not be feasible, because the test is not widely available, and, most importantly, the disease is associated with both the presence of allelic and locus heterogeneity. Further studies with this population of patients are required to expand the use of related donors in MSUD.

Mucopolysaccharidosis type II: identification of 30 novel mutations among Latin American patients.

In this study, 103 unrelated South-American patients with mucopolysaccharidosis type II (MPS II) were investigated aiming at the identification of iduronate-2-sulfatase (IDS) disease causing mutations and the possibility of some insights on the genotype-phenotype correlation The strategy used for genotyping involved the identification of the previously reported inversion/disruption of the IDS gene by PCR and screening for other mutations by PCR/SSCP. The exons with altered mobility on SSCP were sequenced, as well as all the exons of patients with no SSCP alteration. By using this strategy, we were able to find the pathogenic mutation in all patients. Alterations such as inversion/disruption and partial/total deletions of the IDS gene were found in 20/103 (19%) patients. Small insertions/deletions/indels (<22 bp) and point mutations were identified in 83/103 (88%) patients, including 30 novel mutations; except for a higher frequency of small duplications in relation to small deletions, the frequencies of major and minor alterations found in our sample are in accordance with those described in the literature.

Mucolipidosis II and III alpha/beta in Brazil: analysis of the GNPTAB gene.

UNLABELLED: Mucolipidosis II and III (MLII and MLIII) alpha/beta are rare autosomal recessive lysosomal storage diseases (LSDs) caused by pathogenic variations in the GNPTAB gene. GNPTAB gene codes for the α and ß subunits of phosphotransferase, the enzyme responsible for synthesis of the mannose-6-phosphate (M6P) marker that directs lysosomal enzymes to the lysosome. OBJECTIVES: The objective of this study is to identify sequence variations of the GNPTAB gene in Brazilian patients with MLII and MLIII alpha/beta. METHOD: Sequencing of the GNPTAB gene was performed in samples of gDNA extracted from the peripheral blood of patients with MLII/III diagnosed at a national reference center for LSDs. RESULTS: Twelve unrelated patients, from several regions of Brazil, were included in this study. Only one was born of consanguineous parents. All patients were found to carry at least one nonpathogenic variation. Nine causal sequence variations were found: c.242G>T (p.W81L); c.1123C>T (p.R375X); c.1196C>T (p.S399F); c.1208T>C (p.I403T); c.1514G>A (p.C505Y); c.1759C>T (p.R587X); c.2808A>G (p.Y937_M972del, novel mutation); c. 2269_2273delGAAAC (p.E757KfsX2, novel mutation); and c.3503_3504delTC (p.L1168QfsX5). Both pathogenic variations were identified in 8 of 12 patients; in four patients, only one pathogenic variation was identified. Mutation c.3503_3504delTC, located in exon 19, was the most frequent pathogenic variation found (n=11/24 alleles). The deleterious effect of the c.2808A>C mutation on splicing was confirmed by cDNA analysis. DISCUSSION/CONCLUSIONS: Our findings confirm that the GNPTAB gene presents broad allelic heterogeneity and suggests that, in Brazilian ML II and III patients, screening for mutations should begin at exon 19 of the GNPTAB gene. Further analyses will be conducted on patients in whom both pathogenic mutations have not been found in this study.

Enzyme replacement therapy for mucopolysaccharidosis VI: long-term cardiac effects of galsulfase (Naglazyme®) therapy.

Characteristic cardiac valve abnormalities and left ventricular hypertrophy are present in untreated patients with mucopolysaccharidosis type VI (MPS VI). Cardiac ultrasound was performed to investigate these findings in subjects during long-term enzyme replacement therapy (ERT) with recombinant human arylsulfatase B (rhASB, rhN-acetylgalactosamine 4-sulfatase, galsulfase, Naglazyme®). Studies were conducted in 54 subjects before ERT was begun and at specific intervals for up to 96 weeks of weekly infusions of rhASB at 1 mg/kg during phase 1/2, phase 2, and phase 3 trials of rhASB. At baseline, mitral and aortic valve obstruction was present and was significantly greater in those ≥12 years of age. Mild mitral and trace aortic regurgitation were present, the former being significantly greater in those <12 years. Left ventricular hypertrophy, with averaged z-scores ranging from 1.6-1.9 SD greater than normal, was present for ages both <12 and ≥12 years. After 96 weeks of ERT, ventricular septal hypertrophy regressed in those <12 years. For those ≥12 years, septal hypertrophy was unchanged, and aortic regurgitation increased statistically but not physiologically. Obstructive gradients across mitral and aortic valves remained unchanged. The results suggest that long-term ERT is effective in reducing intraventricular septal hypertrophy and preventing progression of cardiac valve abnormalities when administered to those <12 years of age.

Severity score system for progressive myelopathy: development and validation of a new clinical scale

Progressive myelopathies can be secondary to inborn errors of metabolism (IEM) such as mucopolysaccharidosis, mucolipidosis, and adrenomyeloneuropathy. The available scale, Japanese Orthopaedic Association (JOA) score, was validated only for degenerative vertebral diseases. Our objective is to propose and validate a new scale addressing progressive myelopathies and to present validating data for JOA in these diseases. A new scale, Severity Score System for Progressive Myelopathy (SSPROM), covering motor disability, sphincter dysfunction, spasticity, and sensory losses. Inter- and intra-rater reliabilities were measured. External validation was tested by applying JOA, the Expanded Disability Status Scale (EDSS), the Barthel index, and the Osame Motor Disability Score. Thirty-eight patients, 17 with adrenomyeloneuropathy, 3 with mucopolysaccharidosis I, 3 with mucopolysaccharidosis IV, 2 with mucopolysaccharidosis VI, 2 with mucolipidosis, and 11 with human T-cell lymphotropic virus type-1 (HTLV-1)-associated myelopathy participated in the study. The mean ± SD SSPROM and JOA scores were 74.6 ± 11.4 and 12.4 ± 2.3, respectively. Construct validity for SSPROM (JOA: r = 0.84, P < 0.0001; EDSS: r = -0.83, P < 0.0001; Barthel: r = 0.56, P < 0.002; Osame: r = -0.94, P < 0.0001) and reliability (intra-rater: r = 0.83, P < 0.0001; inter-rater: r = 0.94, P < 0.0001) were demonstrated. The metric properties of JOA were similar to those found in SSPROM. Several clinimetric requirements were met for both SSPROM and JOA scales. Since SSPROM has a wider range, it should be useful for follow-up studies on IEM myelopathies.

Severity score system for progressive myelopathy: development and validation of a new clinical scale.

Progressive myelopathies can be secondary to inborn errors of metabolism (IEM) such as mucopolysaccharidosis, mucolipidosis, and adrenomyeloneuropathy. The available scale, Japanese Orthopaedic Association (JOA) score, was validated only for degenerative vertebral diseases. Our objective is to propose and validate a new scale addressing progressive myelopathies and to present validating data for JOA in these diseases. A new scale, Severity Score System for Progressive Myelopathy (SSPROM), covering motor disability, sphincter dysfunction, spasticity, and sensory losses. Inter- and intra-rater reliabilities were measured. External validation was tested by applying JOA, the Expanded Disability Status Scale (EDSS), the Barthel index, and the Osame Motor Disability Score. Thirty-eight patients, 17 with adrenomyeloneuropathy, 3 with mucopolysaccharidosis I, 3 with mucopolysaccharidosis IV, 2 with mucopolysaccharidosis VI, 2 with mucolipidosis, and 11 with human T-cell lymphotropic virus type-1 (HTLV-1)-associated myelopathy participated in the study. The mean ± SD SSPROM and JOA scores were 74.6 ± 11.4 and 12.4 ± 2.3, respectively. Construct validity for SSPROM (JOA: r = 0.84, P < 0.0001; EDSS: r = -0.83, P < 0.0001; Barthel: r = 0.56, P < 0.002; Osame: r = -0.94, P < 0.0001) and reliability (intra-rater: r = 0.83, P < 0.0001; inter-rater: r = 0.94, P < 0.0001) were demonstrated. The metric properties of JOA were similar to those found in SSPROM. Several clinimetric requirements were met for both SSPROM and JOA scales. Since SSPROM has a wider range, it should be useful for follow-up studies on IEM myelopathies.

Origin and spread of a common deletion causing mucolipidosis type II: insights from patterns of haplotypic diversity.

Mucolipidosis II (ML II alpha/beta), or I-cell disease, is a rare genetic disease in which activity of the uridine diphosphate (UDP)-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) is absent. GlcNAc-phosphotransferase is a multimeric enzyme encoded by two genes, GNPTAB and GNPTG. A spectrum of mutations in GNPTAB has been recently reported to cause ML II alpha/beta. Most of these mutations were found to be private or rare. However, the mutation c.3503_3504delTC has been detected among Israeli and Palestinian Arab-Muslim, Turkish, Canadian, Italian, Portuguese, Irish traveller and US patients. We analysed 44 patients who were either homozygous or compound heterozygous for this deletion (22 Italians, 8 Arab-Muslims, 1 Turk, 3 Argentineans, 3 Brazilians, 2 Irish travellers and 5 Portuguese) and 16 carriers (15 Canadians and 1 Italian) for three intragenic polymorphisms: c.-41_-39delGGC, c.18G>A and c.1932A>G as well as two microsatellite markers flanking the GNPTAB gene (D12S1607 and D12S1727). We identified a common haplotype in all chromosomes bearing the c.3503_3504delTC mutation. In summary, we showed that patients carrying the c.3503_3504delTC deletion presented with a common haplotype, which implies a common origin of this mutation. Additionally, the level of diversity observed at the most distant locus indicates that the mutation is relatively ancient (around 2063 years old), and the geographical distribution further suggests that it probably arose in a peri-Mediterranean region.

Evidence that L-carnitine and selenium supplementation reduces oxidative stress in phenylketonuric patients.

It is well established that the involvement of reactive species in the pathophysiology of several neurological diseases, including phenylketonuria (PKU), a metabolic genetic disorder biochemically characterized by elevated levels of phenylalanine (Phe). In previous studies, we verified that PKU patients (treated with a protein-restricted diet supplemented with a special formula not containing L-carnitine and selenium) presented high lipid and protein oxidative damage as well as a reduction of antioxidants when compared to the healthy individuals. Our goal in the present study was to evaluate the effect of Phe-restricted diet supplemented with L-carnitine and selenium, two well-known antioxidant compounds, on oxidative damage in PKU patients. We investigated various oxidative stress parameters in blood of 18 treated PKU patients before and after 6 months of supplementation with a special formula containing L-carnitine and selenium. It was verified that treatment with L-carnitine and selenium was capable of reverting the lipid peroxidation, measured by thiobarbituric acid-reactive species, and the protein oxidative damage, measured by sulfhydryl oxidation, to the levels of controls. Additionally, the reduced activity of glutathione peroxidase was normalized by the antioxidant supplementation. It was also verified a significant inverse correlation between lipid peroxidation and L-carnitine blood levels as well as a significant positive correlation between glutathione peroxidase activity and blood selenium concentration. In conclusion, our results suggest that supplementation of L-carnitine and selenium is important for PKU patients since it could help to correct the oxidative stress process which possibly contributes, at least in part, to the neurological symptoms found in phenylketonuric patients.

The management of Gaucher disease in developing countries: a successful experience in Southern Brazil.

OBJECTIVE: Gaucher disease (GD) is a genetic disease caused by glucocerebrosidase deficiency. GD is treated by enzyme replacement therapy (ERT) with imiglucerase, a high-cost drug provided by the Brazilian Ministry of Health (BMH). This study reports the implementation of the BMH guidelines for GD in the southernmost state of the country. METHODS: We review the clinical and laboratorial data for patients seen at the reference center for GD from Rio Grande do Sul, Brazil (July 2003 to June 2006). RESULTS: Twenty-five patients were included in this study. At baseline, 19/20 were on ERT (mean dosage of imiglucerase = 51.8 U/kg/infusion), 3/17 presented anemia, and 5/16 thrombocytopenia. The amount of imiglucerase prescribed to these patients was adjusted according to the guidelines in July 2003; out of them, 18 were receiving ERT in the reference center at month 36 (mean dosage of imiglucerase = 27.5 U/kg/infusion), 2/18 presented anemia, and 4/18 presented thrombocytopenia. The analysis of the liver, spleen, and bone data presented some limitations, but the available information suggests that patients did not deteriorate. GD patients who initiated ERT after July 2003 (n = 5) received lower dosage of imiglucerase since the beginning of the treatment; most of them demonstrated clinical and laboratorial response. From baseline to month 36, the consumption of imiglucerase by the reference center showed a significant reduction, which represented savings of USD 3 million to the public health system. CONCLUSIONS: The model of care of GD patients suggested by the BMH guidelines appears to be cost-effective and could be an example for management of rare diseases in underdeveloped countries.

Multidisciplinary management of Hunter syndrome.

Hunter syndrome is a rare, X-linked disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase. In the absence of sufficient enzyme activity, glycosaminoglycans accumulate in the lysosomes of many tissues and organs and contribute to the multisystem, progressive pathologies seen in Hunter syndrome. The nervous, cardiovascular, respiratory, and musculoskeletal systems can be involved in individuals with Hunter syndrome. Although the management of some clinical problems associated with the disease may seem routine, the management is typically complex and requires the physician to be aware of the special issues surrounding the patient with Hunter syndrome, and a multidisciplinary approach should be taken. Subspecialties such as otorhinolaryngology, neurosurgery, orthopedics, cardiology, anesthesiology, pulmonology, and neurodevelopment will all have a role in management, as will specialty areas such as physiotherapy, audiology, and others. The important management topics are discussed in this review, and the use of enzyme-replacement therapy with recombinant human iduronate-2-sulfatase as a specific treatment for Hunter syndrome is presented.