Implementation of newborn screening for mucopolysaccharidosis type IVA and long-term monitoring in Taiwan.

PURPOSE: Mucopolysaccharidosis IVA (MPS IVA) is a rare lysosomal storage disorder arising from a deficiency in N-acetylgalactosamine-6-sulfatase. METHODS: From September 2019 to October 2023, a total of 264,843 Taiwanese newborns underwent screening for MPS IVA using dried blood spots and tandem mass spectrometry. RESULTS: Among the 95 referred infants, 9 (9%) were confirmed to have MPS IVA (group 1), 18 (19%) were highly suspected to have MPS IVA (group 2), 61 (64%) were identified as heterozygotes of MPS IVA (group 3), and 7 (7%) were determined not to have MPS IVA (group 4). A total of 34 different GALNS (HGNC:4122) gene variants were identified through our MPS IVA newborn screening program. The most prevalent variant was c.857C>T p.(Thr286Met), found in 33 cases (29%), followed by c.953T>G p.(Met318Arg) in 22 cases (19%). Intravenous enzyme replacement therapy was initiated in 5 patients at ages ranging from 0.3 to 1.7 years. The estimated incidence of MPS IVA in this screening program was 3.4 per 100,000 live births. CONCLUSION: Because of the progressive nature of MPS IVA, an early diagnosis facilitated by newborn screening and prompt initiation of enzyme replacement therapy before irreversible organ damage occurs may result in improved clinical outcomes.

Genetic and Phenotypic Spectrum of KMT2D Variants in Taiwanese Case Series of Kabuki Syndrome.

Kabuki syndrome (KS) is a rare genetic disorder characterized by distinct facial features, intellectual disability, and multiple congenital anomalies. We conducted a comprehensive analysis of the genetic and phenotypic spectrum of KS in a Taiwanese patient group of 23 patients. KMT2D variants were found in 22 individuals, with missense (26.1%), nonsense (21.7%), and frameshift (17.4%) variants being the most prevalent. One patient had a KMT2D variant of uncertain significance. The most common clinical characteristics included distinct facial features (100%), intellectual disability (100%), developmental delay (95.7%), speech delay (78.3%), hypotonia (69.6%), congenital heart abnormalities (69.6%), and recurrent infections (65.2%). Other abnormalities included hearing loss (39.1%), seizures (26.1%), cleft palate (26.1%), and renal anomalies (21.7%). This study broadens the mutational and phenotypic spectrum of KS in the Taiwanese population, highlighting the importance of comprehensive genetic testing and multidisciplinary clinical evaluations for diagnosis and treatment.

Multisystem disorder associated with a pathogenic variant in CLCN7 in the absence of osteopetrosis.

BACKGROUND: We clinically and genetically evaluated a Taiwanese boy presenting with developmental delay, organomegaly, hypogammaglobulinemia and hypopigmentation without osteopetrosis. Whole-exome sequencing revealed a de novo gain-of-function variant, p.Tyr715Cys, in the C-terminal domain of ClC-7 encoded by CLCN7. METHODS: Nicoli et al. (2019) assessed the functional impact of p.Tyr715Cys by heterologous expression in Xenopus oocytes and evaluating resulting currents. RESULTS: The variant led to increased outward currents, indicating it underlies the patient's phenotype of lysosomal hyperacidity, storage defects and vacuolization. This demonstrates the crucial physiological role of ClC-7 antiporter activity in maintaining appropriate lysosomal pH. CONCLUSION: Elucidating mechanisms by which CLCN7 variants lead to lysosomal dysfunction will advance understanding of genotype-phenotype correlations. Identifying modifier genes and compensatory pathways may reveal therapeutic targets. Ongoing functional characterization of variants along with longitudinal clinical evaluations will continue advancing knowledge of ClC-7's critical roles and disease mechanisms resulting from its dysfunction. Expanded cohort studies are warranted to delineate the full spectrum of associated phenotypes.

Application of whole exome sequencing in the diagnosis of muscular disorders: a study of Taiwanese pediatric patients.

Background: Muscular dystrophies and congenital myopathies encompass various inherited muscular disorders that present diagnostic challenges due to clinical complexity and genetic heterogeneity. Methods: This study aimed to investigate the use of whole exome sequencing (WES) in diagnosing muscular disorders in pediatric patients in Taiwan. Out of 161 pediatric patients suspected to have genetic/inherited myopathies, 115 received a molecular diagnosis through conventional tests, single gene testing, and gene panels. The remaining 46 patients were divided into three groups: Group 1 (multiplex ligation-dependent probe amplification-negative Duchenne muscular dystrophy) with three patients (6.5%), Group 2 (various forms of muscular dystrophies) with 21 patients (45.7%), and Group 3 (congenital myopathies) with 22 patients (47.8%). Results: WES analysis of these groups found pathogenic variants in 100.0% (3/3), 57.1% (12/21), and 68.2% (15/22) of patients in Groups 1 to 3, respectively. WES had a diagnostic yield of 65.2% (30 patients out of 46), detecting 30 pathogenic or potentially pathogenic variants across 28 genes. Conclusion: WES enables the diagnosis of rare diseases with symptoms and characteristics similar to congenital myopathies and muscular dystrophies, such as muscle weakness. Consequently, this approach facilitates targeted therapy implementation and appropriate genetic counseling.

Mature neurons from iPSCs unveil neurodegeneration-related pathways in mucopolysaccharidosis type II: GSK-3ß inhibition for therapeutic potential.

Mucopolysaccharidosis (MPS) type II is caused by a deficiency of iduronate-2-sulfatase and is characterized by the accumulation of glycosaminoglycans (GAGs). Without effective therapy, the severe form of MPS II causes progressive neurodegeneration and death. This study generated multiple clones of induced pluripotent stem cells (iPSCs) and their isogenic controls (ISO) from four patients with MPS II neurodegeneration. MPS II-iPSCs were successfully differentiated into cortical neurons with characteristic biochemical and cellular phenotypes, including axonal beadings positive for phosphorylated tau, and unique electrophysiological abnormalities, which were mostly rescued in ISO-iPSC-derived neurons. RNA sequencing analysis uncovered dysregulation in three major signaling pathways, including Wnt/ß-catenin, p38 MAP kinase, and calcium pathways, in mature MPS II neurons. Further mechanistic characterization indicated that the dysregulation in calcium signaling led to an elevated intracellular calcium level, which might be linked to compromised survival of neurons. Based on these dysregulated pathways, several related chemicals and drugs were tested using this mature MPS II neuron-based platform and a small-molecule glycogen synthase kinase-3ß inhibitor was found to significantly rescue neuronal survival, neurite morphology, and electrophysiological abnormalities in MPS II neurons. Our results underscore that the MPS II-iPSC-based platform significantly contributes to unraveling the mechanisms underlying the degeneration and death of MPS II neurons and assessing potential drug candidates. Furthermore, the study revealed that targeting the specific dysregulation of signaling pathways downstream of GAG accumulation in MPS II neurons with a well-characterized drug could potentially ameliorate neuronal degeneration.

Illuminating the Genetic Basis of Congenital Heart Disease in Patients with Kabuki Syndrome.

Congenital heart defects (CHDs) affect a substantial proportion of patients with Kabuki syndrome. However, the prevalence and type of CHD and the genotype-phenotype correlations in Asian populations are not fully elucidated. This study performed a retrospective analysis of 23 Taiwanese patients with molecularly confirmed Kabuki syndrome. Twenty-two patients presented with pathogenic variants in the KMT2D gene. Comprehensive clinical assessments were performed. A literature review was conducted to summarize the spectrum of CHDs in patients with Kabuki syndrome. In total, 16 (73.9%) of 22 patients with pathogenic KMT2D variants had CHDs. The most common types of CHD were atrial septal defects (37.5%), ventricular septal defects (18.8%), coarctation of the aorta (18.8%), bicuspid aortic valve (12.5%), persistent left superior vena cava (12.5%), mitral valve prolapse (12.5%), mitral regurgitation (12.5%), and patent ductus arteriosus (12.5%). Other cardiac abnormalities were less common. Further, there were no clear genotype-phenotype correlations found. A literature review revealed similar patterns of CHDs, with a predominance of left-sided obstructive lesions and septal defects. In conclusion, the most common types of CHDs in Taiwanese patients with Kabuki syndrome who presented with KMT2D mutations are left-sided obstructive lesions and septal defects.

Quantitative DNA Methylation Analysis and Epigenotype-Phenotype Correlations in Taiwanese Patients with Silver-Russell Syndrome.

Background: Silver-Russell syndrome (SRS; OMIM #180860) is a clinically and genetically heterogeneous imprinting disorder characterized by prenatal and postnatal growth failure. The aim of this study was to identify the epigenotype-phenotype correlations in these patients using quantitative DNA methylation analysis. Methods: One hundred and eighty-three subjects clinically suspected of having SRS were referred for diagnostic testing by the methylation profiling of H19-associated imprinting center (IC) 1 and imprinted PEG1/MEST regions using methylation-specific high-resolution melting analysis and methylation quantification with the MassARRAY assay. Correlations between quantitative DNA methylation status and clinical manifestations of the subjects according to the Netchine-Harbison (N-H) clinical scoring system for SRS were analyzed. Results: Among the 183 subjects, 90 had a clinical diagnosis of SRS [N-H score ≥ 4 (maximum = 6)] and 93 had an SRS score < 4. Molecular lesions were detected in 41% (37/90) of the subjects with a clinical diagnosis of SRS, compared with 3% (3/93) of those with an N-H score < 4. The IC1 methylation level was negatively correlated with the N-H score. The molecular diagnosis rate was positively correlated with the N-H score. Thirty-one subjects had IC1 hypomethylation (IC1 methylation level <35% by the MassARRAY assay), seven had maternal uniparental disomy 7, and two had pathogenic copy number variants. Among the 90 subjects with an N-H score ≥ 4, the IC1 methylation level was significantly different between those with or without some clinical SRS features, including birth length ≤ 10th centile, relative macrocephaly at birth, normal cognitive development, body asymmetry, clinodactyly of the fifth finger, and genital abnormalities. Conclusions: This study confirmed the suitability of the N-H clinical scoring system as clinical diagnostic criteria for SRS. Quantitative DNA methylation analysis using the MassARRAY assay can improve the detection of epigenotype-phenotype correlations, further promoting better genetic counseling and multidisciplinary management for these patients.

Spectrum of PHEX Mutations and FGF23 Profiles in a Taiwanese Cohort With X-Linked Hypophosphatemia Including 102 Patients.

BACKGROUND/AIM: X-linked hypophosphatemia (XLH), the most common form of hereditary rickets, results from loss-of-function mutations in the phosphate-regulating PHEX gene. Elevated fibroblast growth factor 23 (FGF23) contributes to hypophosphatemia in XLH. This study aimed to characterize PHEX variants and serum FGF23 profiles in Taiwanese patients with XLH. PATIENTS AND METHODS: We retrospectively reviewed the records of 102 patients clinically suspected of having hypophosphatemic rickets from 2006 to 2022. Serum intact Fibroblast growth factor-23 (iFGF23) levels were measured on clinic visit days. PHEX mutations were identified using Sanger sequencing, and negative cases were analyzed using whole-exome sequencing. RESULTS: The majority (92.1%) of patients exhibited elevated FGF23 compared with normal individuals. Among 102 patients, 44 distinct PHEX mutations were identified. Several mutations recurred in multiple unrelated Taiwanese families. We discovered a high frequency of novel PHEX mutations and identified variants associated with extreme FGF23 elevation and tumorigenesis. CONCLUSION: Our findings revealed the PHEX genotypic variants and FGF23 levels in Taiwanese patients with XLH. These results are crucial given the recent approval of burosumab, a monoclonal FGF23 antibody, for XLH therapy. This study provides key insights into the clinical management of XLH in Taiwan.

Phenotype, genotype, and clinical outcome of Taiwanese with congenital nephrotic syndrome.

BACKGROUND/PURPOSE: Congenital nephrotic syndrome (CNS) is one of the important causes of end-stage kidney disease in children. Studies on the genotype, phenotype, and clinical outcome in infants with CNS caused by genetic mutations are scarce. METHODS: We analyzed the genetic background, clinical manifestations, treatment response, and prognosis of pediatric patients with CNS in Taiwan. RESULTS: Fifteen infants with CNS were enrolled, and 11 patients of median age 21 (interquartile range 3∼44) days caused by genetic mutations from 10 unrelated families were included in the study. Of the eleven patients, 9 had extra-renal manifestations including microcephaly, facial dysmorphism, and skeletal anomalies. More than two-thirds of the patients had disease onset before 1 month of age. Diffuse meningeal sclerosis was the most common histological characteristic. Whole exome sequencing followed by direct Sanger sequence revealed mutations in OSGEP (R247Q), WT1 (R366H and R467Q), LAMB2 (Q1209∗ and c. 5432-5451 19 bp deletion), NUP93 (D302V), and LAGE3 (c.188+1G > A). Three of the variants were novel. Corticosteroids and/or immunosuppressants were administered in 2 patients, but both were refractory to treatment. During the mean 3.5 years of follow-up, all but two died of uremia and sepsis. The two survivors reached end-stage kidney disease and required peritoneal dialysis, and one of them underwent uneventful renal transplantation. CONCLUSIONS: The majority of patients with CNS in Taiwan were caused by OSGEP followed by WT1 mutation. R247Q is the hotspot mutation of OSGEP in Taiwan. CNS patients in Taiwan suffer from significant morbidity and mortality.

22q11.2 Deletion Syndrome in Taiwan: Clinical Presentation and Immune System Status of Patients.

Background: 22q11.2 deletion syndrome (22q11.2DS) is a microdeletion syndrome exhibiting significant clinical phenotype variability. This study aimed to investigate the clinical features, immune profiles, and cognitive abilities of 22q11.2DS patients receiving treatment at MacKay Memorial Hospital in Taipei, Taiwan. Methods: This is a cross-sectional analysis between January 2001 and December 2022. We recruited 27 patients with 22q11.2DS using fluorescence in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA) and array comparative genomic hybridization (aCGH). Our evaluation included patient history, physical examination, laboratory analysis, and cardiac and cognitive assessment. Results: We included 27 patients with 22q11.2DS, 7 (25.9%) of whom were female. The median age of the patients was 17.9 yr. Ninety-three percent of the patients exhibited the characteristic facial features associated with the syndrome. A family history of 22q11.2DS was found in 11.1% of the patients. Furthermore, 74.1% of the patients had a congenital heart defect, the most common of which was tetralogy of Fallot (40.7%). Hypocalcemia was observed in 40.7% of the patients. A low T-cell count was observed in 66.7% of the patients, whereas 18.5% had low immunoglobulin levels. Cognitive assessments revealed that four out of six evaluated patients (66.7%) had an intellectual disability, as evidenced by intellectual quotient scores less than 70. The remaining two patients (33.3%) had a borderline intellectual function. Conclusion: Tetralogy of Fallot, hypocalcemia, immunologic defects, and cognitive impairment were common among our patients. To address the potential multisystem involvement, we recommend that all affected individuals undergo a comprehensive evaluation by a multidisciplinary care team.

Genetic counseling of a prenatally detected familial 18.79-kb Xp21.1 microduplication encompassing exon 13 of DMD in a pregnancy with no apparent phenotypic abnormalities in the male carriers in the family.

OBJECTIVE: We present genetic counseling of a prenatally detected familial 18.79-kb Xp21.1 microduplication encompassing exon 13 of DMD in a pregnancy with no apparent phenotypic abnormalities in the male carriers in the family. CASE REPORT: A 35-year-old, gravida 2, para 0, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes revealed an 18.79-kb Xp21.1 microduplication, or arr Xp21.1 (32,608,400-32,627,193) × 2.0 [GRCh37 (hg19)] encompassing only exon 13 of the gene of DMD (31,137,345-33,357,706) [GRCh37 (hg19)]. Multiplex ligation-dependent probe amplification (MLPA) analysis of the family showed that the mother and her 32-year-old brother carried the same duplication but without apparent phenotypic abnormalities and no features of DMD. Prenatal ultrasound was normal. She was referred for genetic counseling at 24 weeks of gestation, and continuing pregnancy was advised. At 38 weeks of gestation, a 3530-g phenotypically normal male baby was delivered. aCGH analysis of the umbilical cord confirmed the result of arr Xp21.1 (32,608,400-32,627,193) × 2.0 [GRCh37 (hg19)] encompassing only exon 13 of the gene of DMD (31,137,345-33,357,706) [GRCh37 (hg19)]. CONCLUSION: Xp21.1 microduplication encompassing exon 13 of the DMD gene can be a benign genetic variant.

Endoscopic and Image Analysis of the Airway in Patients with Mucopolysaccharidosis Type IVA.

Mucopolysaccharidosis (MPS) is a hereditary disorder arising from lysosomal enzymes deficiency, with glycosaminoglycans (GAGs) storage in connective tissues and bones, which may compromise the airway. This retrospective study evaluated patients with MPS type IVA with airway obstruction detected via endoscopy and imaging modalities and the effects of surgical interventions based on symptoms. The data of 15 MPS type IVA patients (10 males, 5 females, mean age 17.8 years) were reviewed in detail. Fiberoptic bronchoscopy (FB) was used to distinguish adenotonsillar hypertrophy, prolapsed soft palate, secondary laryngomalacia, vocal cord granulation, cricoid thickness, tracheal stenosis, shape of tracheal lumen, nodular deposition, tracheal kinking, tracheomalacia with rigid tracheal wall, and bronchial collapse. Computed tomography (CT) helped to measure the deformed sternal angle, the cross-sectional area of the trachea, and its narrowest/widest ratio (NW ratio), while angiography with 3D reconstruction delineated tracheal torsion, kinking, or framework damage and external vascular compression of the trachea. The NW ratio correlated negatively with age (p < 0.01), showing that airway obstruction progressed gradually. Various types of airway surgery were performed to correct the respiratory dysfunction. MPS type IVA challenges the management of multifactorial airway obstruction. Preoperative airway evaluation with both FB and CT is strongly suggested to assess both intraluminal and extraluminal factors causing airway obstruction.

Utility of whole-exome sequencing for patients with multiple congenital anomalies with or without intellectual disability/developmental delay in East Asia population.

BACKGROUND: Congenital anomalies (CAs) with or without intellectual disability (ID)/developmental delay (DD) comprise a heterogeneous spectrum of diseases that affect approximately 3% of live births worldwide. Recently, whole-exome sequencing (WES) demonstrated the highly heterogeneous genetic causes of CAs. The purpose of this study was to evaluate a referral system to increase the yield of WES for CAs. METHODS: From August 2018 to July 2019, patients with CAs, with or without ID/DD, after excluding gross chromosomal aberrations, were referred to geneticists in two medical centers. Variant prioritization was conducted with an AI-assisted tool for whole exomes or a CA-related gene panel. RESULTS: Forty patients (27 males and 13 females) with CAs were enrolled in the study with a mean age of 4.71 years (range, 0.01-18.2). Pathogenic variants in 14 genes were discovered in 16 patients (three patients with CHD7 and 13 patients with one gene each of ATP6V1B2, TAF6, COL4A3BP, ANKH, BMP2, SMARCA4, CUL4B, PGAP3, SOX11, FBN2, PTPN11, SOS1, or PROKR2), with a positive diagnostic rate of 40%. Among the 16 positive cases, 13 (81%) also had ID/DD. The inheritance was autosomal dominant in 13 (81%), autosomal recessive in two (13%), and X-linked in one (6%). Only five patients received a correct clinical diagnosis before WES. The analyses of patients with a negative genetic diagnosis revealed a phenotype and gene mutation load similar to those of the positive-finding patients but with a lower percentage of ID/DD. CONCLUSIONS: The careful selection of patients by experienced geneticists and the exclusion of chromosomal aberrations raises the positive rate of the molecular diagnosis for CAs to 40%. However, more than half of the patients with CAs still do not have a genetic diagnosis by current technologies.

Discovery of small-molecule protein stabilizers toward exogenous alpha-l-iduronidase to reduce the accumulated heparan sulfate in mucopolysaccharidosis type I cells.

Synthesis of a series of l-iduronic acid (IdoA)- and imino-IdoA-typed C-glycosides for modulating α-l-iduronidase (IDUA) activity is described. In an enzyme inhibition study, IdoA-typed C-glycosides were more potent than imino-IdoA analogs, with the most potent IdoA-typed C-glycoside 27c showing an IC50 value of 1 µM. On the other hand, co-treatment of 12 with rh-α-IDUA in mucopolysaccharidosis type I (MPS I) fibroblasts exhibited a nearly 3-fold increase of the IDUA activity, resulting in a clear reduction of the accumulated heparan sulfate (HS) compared to the exogenous enzyme treatment alone. This is the first report of small molecules facilitating IDUA stabilization, enhancing enzyme activity, and reducing accumulated HS in MPS I cell-based assays, which reveals that small molecules as rh-α-IDUA stabilizers to improve enzyme replacement therapy (ERT) efficacy toward MPS I is feasible and promising.

A phase I/II study on intracerebroventricular tralesinidase alfa in patients with Sanfilippo syndrome type B.

BackgroundSanfilippo type B is a mucopolysaccharidosis (MPS) with a major neuronopathic component characterized by heparan sulfate (HS) accumulation due to mutations in the NAGLU gene encoding alfa-N-acetyl-glucosaminidase. Enzyme replacement therapy for neuronopathic MPS requires efficient enzyme delivery throughout the brain in order to normalize HS levels, prevent brain atrophy, and potentially delay cognitive decline.MethodsIn this phase I/II open-label study, patients with MPS type IIIB (n = 22) were treated with tralesinidase alfa administered i.c.v. The patients were monitored for drug exposure; total HS and HS nonreducing end (HS-NRE) levels in both cerebrospinal fluid (CSF) and plasma; anti-drug antibody response; brain, spleen, and liver volumes as measured by MRI; and cognitive development as measured by age-equivalent (AEq) scores.ResultsIn the Part 1 dose escalation (30, 100, and 300 mg) phase, a 300 mg dose of tralesinidase alfa was necessary to achieve normalization of HS and HS-NRE levels in the CSF and plasma. In Part 2, 300 mg tralesinidase alfa sustained HS and HS-NRE normalization in the CSF and stabilized cortical gray matter volume (CGMV) over 48 weeks of treatment. Resolution of hepatomegaly and a reduction in spleen volume were observed in most patients. Significant correlations were also established between the change in cognitive AEq score and plasma drug exposure, plasma HS-NRE levels, and CGMV.ConclusionAdministration of tralesinidase alfa i.c.v. effectively normalized HS and HS-NRE levels as a prerequisite for clinical efficacy. Peripheral drug exposure data suggest a role for the glymphatic system in altering tralesinidase alfa efficacy.Trial registrationClinicaltrials.gov NCT02754076.FUNDINGBioMarin Pharmaceutical Inc. and Allievex Corporation.

De Novo Mosaic 6p23-p25.3 Tetrasomy Caused by a Small Supernumerary Marker Chromosome Presenting Trisomy Distal 6p Phenotype: A Case Report and Literature Review.

Small supernumerary marker chromosomes (sSMCs) derived from the chromosome 6 short arm are rare and their clinical significance remains unknown. No case with sSMC(6) without centromeric DNA has been reported. Partial trisomy and tetrasomy of distal 6p is a rare but clinically distinct syndrome. We report on a de novo mosaic sSMC causing partial tetrasomy for 6p23-p25.3 in a male infant with symptoms of being small for gestational age, microcephaly, facial dysmorphism, congenital eye defects, and multi-system malformation. Conventional cytogenetic analysis revealed a karyotype of 47,XY,+mar [25]/46,XY [22]. Array comparative genomic hybridization (aCGH) revealed mosaic tetrasomy of distal 6p. This is the first case of mosaic tetrasomy 6p23-p25.3 caused by an inverted duplicated neocentric sSMC with characteristic features of trisomy distal 6p. Comparison of phenotypes in cases with trisomy and tetrasomy of 6p23-p25.3 could facilitate a genotype-phenotype correlation and identification of candidate genes contributing to their presentation. The presentation of anterior segment dysgenesis and anomaly of the renal system suggest triplosensitivity of the FOXC1 gene. In patients with microcephaly growth retardation, and malformation of the cardiac and renal systems, presentation of anterior segment dysgenesis might be indicative of chromosome 6p duplication, and aCGH evaluation should be performed for associated syndromic disease.

Updated Confirmatory Diagnosis for Mucopolysaccharidoses in Taiwanese Infants and the Application of Gene Variants.

Mucopolysaccharidosis (MPS) is a lysosomal storage disease caused by genetic defects that result in deficiency of one specific enzyme activity, consequently impairing the stepwise degradation of glycosaminoglycans (GAGs). Except for MPS II, the other types of MPS have autosomal recessive inheritance in which two copies of an abnormal allele must be present in order for the disease to develop. In this study, we present the status of variant alleles and biochemistry results found in infants suspected of having MPS I, II, IVA, and VI. A total of 324 suspected infants, including 12 for MPS I, 223 for MPS II, 72 for MPS IVA, and 17 for MPS VI, who were referred for MPS confirmation from newborn screening centers in Taiwan, were enrolled. In all of these infants, one specific enzyme activity in dried blood spot filter paper was lower than the cut-off value in the first blood sample, as well asin a second follow-up sample. The confirmatory methods used in this study included Sanger sequencing, next-generation sequencing, leukocyte enzyme fluorometric assay, and GAG-derived disaccharides in urine using tandem mass spectrometry assays. The results showed that five, nine, and six infants had MPS I, II, and IVA, respectively, and all of them were asymptomatic. Thus, a laboratory diagnosis is extremely important to confirm the diagnosis of MPS. The other infants with identified nucleotide variations and reductions in leukocyte enzyme activities were categorized as being highly suspected cases requiring long-term and intensive follow-up examinations. In summary, the final confirmation of MPS depends on the most powerful biomarkers found in urine, i.e., the quantification of GAG-derived disaccharides including dermatan sulfate, heparan sulfate, and keratan sulfate, and analysis of genetic variants can help predict outcomes and guide treatment.

Findings from the Morquio A Registry Study (MARS) after 6 years: Long-term outcomes of MPS IVA patients treated with elosulfase alfa.

BACKGROUND: The Morquio A Registry Study (MARS) is an ongoing, multinational, observational study of patients with MPS IVA. Key objectives of MARS are to characterize the heterogeneity and natural history of disease and to evaluate long-term effectiveness and safety of elosulfase alfa enzyme replacement therapy (ERT). Enrollment began in September 2014; data on medical history, clinical outcomes, and safety assessments are collected as part of routine care. RESULTS: As of February 2021, 381 subjects from 17 countries had enrolled in MARS: 58 ERT-naïve subjects and 323 ERT-treated subjects (≥1 infusion), with a mean ERT exposure of 5.5 years (SD 2.8) and median age at first ERT treatment of 9.8 years. ERT-treated subjects were younger at diagnosis (median 3.4 vs 6.5 years) relative to ERT-naïve subjects. Among ERT-treated subjects, urinary keratan sulfate (uKS) levels declined from pre-ERT baseline to last follow-up on treatment (mean % change [95% confidence interval]: -52.5% [-57.5%, -47.4%]; n = 115) and 6-min walk test distance remained stable (mean change: -6.1 [-27.6, 15.5] m; n = 131) over a mean follow-up of 5.5 years. Forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) increased in subjects who were < 18 years of age at ERT initiation (mean change: +0.3 [0.1, 0.4] L and + 0.4 [0.3, 0.5] L; mean follow-up: ∼6 years; n = 82) and were stable in subjects ≥18 years (mean change: 0.0 [-0.0, 0.1] L and 0.0 [-0.1, 0.1] L; mean follow-up: 4.6 years; n = 38). Overall, 148 (47.1%) ERT-treated subjects experienced ≥1 adverse event (AE) and 110 subjects (35%) reported ≥1 serious AE. Drug-related AEs were reported in 39 (12.4%) subjects; the most common were hypersensitivity (9 subjects [2.9%]), urticaria (8 subjects [2.5%]), and pyrexia (7 subjects [2.2%]). CONCLUSIONS: MARS is the longest and largest observational study of MPS IVA patients to date, with a heterogenous population that is representative of the MPS IVA population overall. Data collected over the first 6 years of MARS provide real-world evidence for long-term stabilization of endurance and respiratory function among ERT-treated patients, with no new safety concerns identified.

Efficacy of Intravenous Elosulfase Alfa for Mucopolysaccharidosis Type IVA: A Systematic Review and Meta-Analysis.

Mucopolysaccharidosis type IVA (MPS IVA or Morquio A), a lysosomal storage disease with an autosomal recessive inherited pattern, is induced by GALNS gene mutations causing deficiency in N-acetylgalactosamine-6-sulfatase activity (GALNS; EC 3.1.6.4). Currently, intravenous (IV) enzyme replacement therapy (ERT) with elosulfase alfa is employed for treating MPS IVA patients. A systematic literature review was conducted to evaluate the efficacy and safety of IV elosulfase alfa for MPS IVA by searching the National Center for Biotechnology Information, U.S. National Library of Medicine National Institutes of Health (PubMed), Excerpta Medica dataBASE, and Cochrane Library databases, limited to clinical trials. Four cohort studies and two randomized controlled trials, with a total of 550 participants (327 on ERT treatment versus 223 on placebo treatment), satisfied the inclusion criteria. Pooled analysis of proportions and confidence intervals were also utilized to systematically review clinical cohort studies and trials. Per the pooled proportions analysis, the difference in means of urinary keratan sulfate (uKS), 6-min walk test, 3-min stair climb test, self-care MPS-Health Assessment Questionnaire, caregiver assistance and mobility, forced vital capacity, the first second of forced expiration, and maximal voluntary ventilation between the ERT and placebo treatment groups were -0.260, -0.102, -0.182, -0.360, -0.408, -0.587, -0.293, -0.311, and -0.213, respectively. Based on the currently available data, our meta-analysis showed that there is uKS, physical performance, quality of life, and respiratory function improvements with ERT in MPS IVA patients. It is optimal to start ERT after diagnosis.