Newborn screening of mucopolysaccharidoses: past, present, and future.

Mucopolysaccharidoses (MPS) are a subtype of lysosomal storage disorders (LSDs) characterized by the deficiency of the enzyme involved in the breakdown of glycosaminoglycans (GAGs). Mucopolysaccharidosis type I (MPS I, Hurler Syndrome) was endorsed by the U.S. Secretary of the Department of Health and Human Services for universal newborn screening (NBS) in February 2016. Its endorsement exemplifies the need to enhance the accuracy of diagnostic testing for disorders that are considered for NBS. The progression of MPS disorders typically incudes irreversible CNS involvement, severe bone dysplasia, and cardiac and respiratory issues. Patients with MPS have a significantly decreased quality of life if untreated and require timely diagnosis and management for optimal outcomes. NBS provides the opportunity to diagnose and initiate treatment plans for MPS patients as early as possible. Most newborns with MPS are asymptomatic at birth; therefore, it is crucial to have biomarkers that can be identified in the newborn. At present, there are tiered methods and different instrumentation available for this purpose. The screening of quick, cost-effective, sensitive, and specific biomarkers in patients with MPS at birth is important. Rapid newborn diagnosis enables treatments to maximize therapeutic efficacy and to introduce immune tolerance during the neonatal period. Currently, newborn screening for MPS I and II has been implemented and/or in pilot testing in several countries. In this review article, historical aspects of NBS for MPS and the prospect of newborn screening for MPS are described, including the potential tiers of screening.

Long-Term Follow-up Posthematopoietic Stem Cell Transplantation in a Japanese Patient with Type-VII Mucopolysaccharidosis.

The effectiveness of hematopoietic stem cell transplantation (HSCT) for type-VII mucopolysaccharidosis (MPS VII, Sly syndrome) remains controversial, although recent studies have shown that it has a clinical impact. In 1998, Yamada et al. reported the first patient with MPS VII, who underwent HSCT at 12 years of age. Here, we report the results of a 22-year follow-up of that patient post-HSCT, who harbored the p.Ala619Val mutation associated with an attenuated phenotype. The purpose of this study was to evaluate changes in physical symptoms, the activity of daily living (ADL), and the intellectual status in the 34-year-old female MPS VII patient post-HSCT, and to prove the long-term effects of HSCT in MPS VII. Twenty-two years after HSCT, the ß-glucuronidase activity in leukocytes remained at normal levels, and urinary glycosaminoglycan excretion was reduced and kept within normal levels. At present, she is capable of sustaining simple conversation, and her intellectual level is equivalent to that of a 6-year-old. She can walk alone and climb upstairs by holding onto a handrail, although she feels mild pain in the hip joint. The cervical vertebrae are fused with the occipital bone, causing dizziness and light-headedness when the neck is bent back. Overall, her clinical condition has been stabilized and kept well for long-term post-HSCT, indicating that HSCT is a therapeutic option for MPS VII.

Newborn screening for mucopolysaccharidoses: Measurement of glycosaminoglycans by LC-MS/MS.

Mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders which can lead to degenerative and irreversible skeletal, cardiovascular, pulmonary, and neurological damage. Current treatments, including hematopoietic stem cell transplantation and enzyme replacement therapy, have been found most effective if administered before clinical symptoms are present, highlighting the urgent need for the development of newborn screening. This study analyzed 18,222 dried blood spot samples from newborns for both enzyme activity and glycosaminoglycan (GAG) concentration levels. GAG levels were measured using liquid chromatography tandem mass spectrometry. Results were compared to our previously established cutoff values for three subtypes of GAGs: dermatan sulfate (DS) and heparan sulfate (HS0S and HSNS). Samples that were high for two of the three GAGs were identified and screened a second time. Samples were also measured for iduronate-2-sulfatase and alfa-L-iduronidase activity. A total of 300 samples were above the established cutoff values for at least two of the three GAGs after the first screening. One sample was determined through clinical and genetic testing to be a true positive for MPS II. The false positive rate after the first GAG screening was 1.64%. A Cochran's formula test showed that the samples available for the second screening were representative samples (p = .0000601). False positive rate after second GAG screening, extrapolated from the representative sample was 0.4%. False positive rate after enzyme activity assay by fluorimetry for IDUA and IDS enzymes was 0.21% and 0.18%. A combination of GAG and enzyme assays provided no false positive and false negative samples. Two-tier screening involving a combination of enzyme activity and multiple GAGs should be considered the gold standard for the diagnosis of MPS patients.

Assessment of Activity of Daily Life in Mucopolysaccharidosis Type II Patients with Hematopoietic Stem Cell Transplantation.

The effectiveness of hematopoietic stem cell transplantation (HSCT) for mucopolysaccharidosis type II (MPS II, Hunter disease) remains controversial although recent studies have shown HSCT provides more clinical impact. This study aims to evaluate the long-term effectiveness of HSCT using the activity of daily living (ADL) scores in patients with MPS II. Sixty-nine severely affected MPS II patients (19 patients who received HSCT and 50 untreated patients) and 40 attenuated affected patients (five with HSCT and 35 untreated) were investigated by a simplified ADL questionnaire. The frequency of clinical findings and the scores of ADL (verbal, gross motor, and the level of care) were analyzed statistically. The mean age of onset of 19 severely affected patients who received HSCT was 1.40 years ± 1.06, which is not statistically different from that of 50 untreated patients (p = 0.11). Macroglossia, frequent airway infection, hepatosplenomegaly, joint contracture, and sleep apnea were less frequent in the HSCT-treated group of severe MPS II patients. The severe phenotype HSCT treated group reported a statistically significant higher score of verbal function and gross motor function between the ages of 10 and 15 years and a higher level of care score between 10 and 20 years. Patients with the attenuated phenotype showed high ADL scores, and all of five HSCT treated patients reported a lower frequency of frequent airway infection, coarse skin, umbilical/inguinal hernia, hepatosplenomegaly, heart valve disorders, and carpal tunnel. In conclusion, HSCT is effective, resulting in improvements in clinical features and ADL in patients with MPS II. HSCT should be re-reviewed as a therapeutic option for MPS II patients.

Enzyme replacement therapy for mucopolysaccharidoses; past, present, and future.

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders, which lack an enzyme corresponding to the specific type of MPS. Enzyme replacement therapy (ERT) has been the standard therapeutic option for some types of MPS because of the ability to start immediate treatment with feasibility and safety and to improve prognosis. There are several disadvantages for current ERT, such as limited impact to the brain and avascular cartilage, weekly or biweekly infusions lasting 4-5 h, the immune response against the infused enzyme, a short half-life, and the high cost. Clinical studies of ERT have shown limited efficacy in preventing or resolving progression in neurological, cardiovascular, and skeletal diseases. One focus is to penetrate the avascular cartilage area to at least stabilize, if not reverse, musculoskeletal diseases. Although early intervention in some types of MPS has shown improvements in the severity of skeletal dysplasia and stunted growth, this limits the desired effect of ameliorating musculoskeletal disease progression to young MPS patients. Novel ERT strategies are under development to reach the brain: (1) utilizing a fusion protein with monoclonal antibody to target a receptor on the BBB, (2) using a protein complex from plant lectin, glycan, or insulin-like growth factor 2, and (3) direct infusion across the BBB. As for MPS IVA and VI, bone-targeting ERT will be an alternative to improve therapeutic efficacy in bone and cartilage. This review summarizes the effect and limitations on current ERT for MPS and describes the new technology to overcome the obstacles of conventional ERT.

Hematopoietic Stem Cell Transplantation for Mucopolysaccharidoses: Past, Present, and Future.

Allogenic hematopoietic stem cell transplantation (HSCT) has proven to be a viable treatment option for a selected group of patients with mucopolysaccharidoses (MPS), including those with MPS types I, II, IVA, VI, and VII. Early diagnosis and timely referral to an expert in MPS are critical, followed by a complete examination and evaluation by a multidisciplinary team, including a transplantation physician. Treatment recommendations for MPS are based on multiple biological, sociological, and financial factors, including type of MPS, clinical severity, prognosis, present clinical signs and symptoms (disease stage), age at onset, rate of progression, family factors and expectations, financial burden, feasibility, availability, risks and benefits of available therapies such as HSCT, enzyme replacement therapy (ERT), surgical interventions, and other supportive care. International collaboration and data review are critical to evaluating the therapeutic efficacy and adverse effects of HSCT for MPS. Collaborative efforts to assess HSCT for MPS have been ongoing since the first attempt at HSCT in a patient with MPS reported in 1981. The accumulation of data since then has made it possible to identify early outcomes (ie, transplantation outcomes) and long-term disease-specific outcomes resulting from HSCT. The recent identification of predictive factors and the development of innovative regimens have significantly improved the outcomes of both engraftment failure and transplantation-related mortality. Assessment of long-term outcomes has considered a variety of factors, including type of MPS, type of graft, age at transplantation, and stage of disease progression, among others. Studies on long-term outcomes are considered a key factor in the use of HSCT in patients with MPS. These studies have shown the effects and limitations of HSCT on improving disease manifestations and quality of life. In this review, we summarize the efficacy, side effects, risks, and cost of HSCT for each type of MPS.

Molecular genetics and metabolism, special edition: Diagnosis, diagnosis and prognosis of Mucopolysaccharidosis IVA.

Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is an autosomal recessive disorder caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to the accumulation of specific glycosaminoglycans (GAGs), chondroitin-6-sulfate (C6S) and keratan sulfate (KS), which are mainly synthesized in the cartilage. Therefore, the substrates are stored primarily in the cartilage and its extracellular matrix (ECM), leading to a direct impact on bone development and successive systemic skeletal spondylepiphyseal dysplasia. The skeletal-related symptoms for MPS IVA include short stature with short neck and trunk, odontoid hypoplasia, spinal cord compression, tracheal obstruction, obstructive airway, pectus carinatum, restrictive lung, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. The degree of imbalance of growth in bone and other organs and tissues largely contributes to unique skeletal dysplasia and clinical severity. Diagnosis of MPS IVA needs clinical, radiographic, and laboratory testing to make a complete conclusion. To diagnose MPS IVA, total urinary GAG analysis which has been used is problematic since the values overlap with those in age-matched controls. Currently, urinary and blood KS and C6S, the enzyme activity of GALNS, and GALNS molecular analysis are used for diagnosis and prognosis of clinical phenotype in MPS IVA. MPS IVA can be diagnosed with unique characters although this disorder relates closely to other disorders in some characteristics. In this review article, we comprehensively describe clinical, radiographic, biochemical, and molecular diagnosis and clinical assessment tests for MPS IVA. We also compare MPS IVA to other closely related disorders to differentiate MPS IVA. Overall, imbalance of growth in MPS IVA patients underlies unique skeletal manifestations leading to a critical indicator for diagnosis.

Growth impairment in mucopolysaccharidoses.

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders that affect regulation of glycosaminoglycan (GAG) processing. In MPS, the lysosomes cannot efficiently break down GAGs, and the specific GAGs accumulated depend on the type of MPS. The level of impairment of breakdown varies between patients, making this one of the many factors that lead to a range of clinical presentations even in the same type of MPS. These clinical presentations usually involve skeletal dysplasia, in which the most common feature is bone growth impairment and successive short stature. Growth impairment occurs due to the deposition and retention of GAGs in bone and cartilage. The accumulation of GAGs in these tissues leads to progressive damage in cartilage that in turn reduces bone growth by destruction of the growth plate, incomplete ossification, and imbalance of growth. Imbalance of growth leads to various skeletal abnormalities including disproportionate dwarfism with short neck and trunk, prominent forehead, rigidity of joints, tracheal obstruction, kyphoscoliosis, pectus carinatum, platyspondyly, round-shaped vertebral bodies or beaking sign, underdeveloped acetabula, wide flared iliac, coxa valgus, flattered capital femoral epiphyses, and genu valgum. If left untreated, skeletal abnormalities including growth impairment result in a significant impact on these patients' quality of life and activity of daily living, leading to high morbidity and severe handicap. This review focuses on growth impairment in untreated patients with MPS. We comprehensively describe the growth abnormalities through height, weight, growth velocity, and BMI in each type of MPS and compare the status of growth with healthy age-matched controls. The timing, the degree, and the difference in growth impairment of each MPS are highlighted to understand the natural course of growth and to evaluate future therapeutic efficacy.

Presentation and Treatments for Mucopolysaccharidosis Type II (MPS II; Hunter Syndrome).

INTRODUCTION: Mucopolysaccharidosis Type II (MPS II; Hunter syndrome) is an X- linked lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS). IDS deficiency leads to primary accumulation of dermatan sulfate (DS) and heparan sulfate (HS). MPS II is both multi-systemic and progressive. Phenotypes are classified as either attenuated or severe (based on absence or presence of central nervous system impairment, respectively). AREAS COVERED: Current treatments available are intravenous enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), anti-inflammatory treatment, and palliative care with symptomatic surgeries. Clinical trials are being conducted for intrathecal ERT and gene therapy is under pre-clinical investigation. Treatment approaches differ based on age, clinical severity, prognosis, availability and feasibility of therapy, and health insurance.This review provides a historical account of MPS II treatment as well as treatment development with insights into benefits and/or limitations of each specific treatment. EXPERT OPINION: Conventional ERT and HSCT coupled with surgical intervention and palliative therapy are currently the treatment options available to MPS II patients. Intrathecal ERT and gene therapy are currently under investigation as future therapies. These investigative treatments are critical to address the limitations in treatment of the central nervous system (CNS).

Hematopoietic Stem Cell Transplantation for Patients with Mucopolysaccharidosis II.

There is limited information regarding the long-term outcomes of hematopoietic stem cell transplantation (HSCT) for mucopolysaccharidosis II (MPS II). In this study, clinical, biochemical, and radiologic findings were assessed in patients who underwent HSCT and/or enzyme replacement therapy (ERT). Demographic data for 146 HSCT patients were collected from 27 new cases and 119 published cases and were compared with 51 ERT and 15 untreated cases. Glycosaminoglycan (GAG) levels were analyzed by liquid chromatography tandem mass spectrometry in blood samples from HSCT, ERT, and untreated patients as well as age-matched controls. Long-term magnetic resonance imaging (MRI) findings were investigated in 13 treated patients (6 ERT and 7 HSCT). Mean age at HSCT was 5.5 years (range, 2 to 21.4 years) in new patients and 5.5 years (range, 10 months to 19.8 years) in published cases. None of the 27 new patients died as a direct result of the HSCT procedure. Graft-versus-host disease occurred in 8 (9%) out of 85 published cases, and 9 (8%) patients died from transplantation-associated complications. Most HSCT patients showed greater improvement in somatic features, joint movements, and activity of daily living than the ERT patients. GAG levels in blood were significantly reduced by ERT and levels were even lower after HSCT. HSCT patients showed either improvement or no progression of abnormal findings in brain MRI while abnormal findings became more extensive after ERT. HSCT seems to be more effective than ERT for MPS II in a wide range of disease manifestations and could be considered as a treatment option for this condition.

Development of Bone Targeting Drugs.

The skeletal system, comprising bones, ligaments, cartilage and their connective tissues, is critical for the structure and support of the body. Diseases that affect the skeletal system can be difficult to treat, mainly because of the avascular cartilage region. Targeting drugs to the site of action can not only increase efficacy but also reduce toxicity. Bone-targeting drugs are designed with either of two general targeting moieties, aimed at the entire skeletal system or a specific cell type. Most bone-targeting drugs utilize an affinity to hydroxyapatite, a major component of the bone matrix that includes a high concentration of positively-charged Ca2+. The strategies for designing such targeting moieties can involve synthetic and/or biological components including negatively-charged amino acid peptides or bisphosphonates. Efficient delivery of bone-specific drugs provides significant impact in the treatment of skeletal related disorders including infectious diseases (osteoarthritis, osteomyelitis, etc.), osteoporosis, and metabolic skeletal dysplasia. Despite recent advances, however, both delivering the drug to its target without losing activity and avoiding adverse local effects remain a challenge. In this review, we investigate the current development of bone-targeting moieties, their efficacy and limitations, and discuss future directions for the development of these specific targeted treatments.

Glycosaminoglycan levels in dried blood spots of patients with mucopolysaccharidoses and mucolipidoses.

Mucopolysaccharidoses (MPSs) and mucolipidoses (ML) are groups of lysosomal storage disorders in which lysosomal hydrolases are deficient leading to accumulation of undegraded glycosaminoglycans (GAGs), throughout the body, subsequently resulting in progressive damage to multiple tissues and organs. Assays using tandem mass spectrometry (MS/MS) have been established to measure GAGs in serum or plasma from MPS and ML patients, but few studies were performed to determine whether these assays are sufficiently robust to measure GAG levels in dried blood spots (DBS) of patients with MPS and ML. MATERIAL AND METHODS: In this study, we evaluated GAG levels in DBS samples from 124 MPS and ML patients (MPS I=16; MPS II=21; MPS III=40; MPS IV=32; MPS VI=10; MPS VII=1; ML=4), and compared them with 115 age-matched controls. Disaccharides were produced from polymer GAGs by digestion with chondroitinase B, heparitinase, and keratanase II. Subsequently, dermatan sulfate (DS), heparan sulfate (HS-0S, HS-NS), and keratan sulfate (mono-sulfated KS, di-sulfated KS, and ratio of di-sulfated KS in total KS) were measured by MS/MS. RESULTS: Untreated patients with MPS I, II, VI, and ML had higher levels of DS compared to control samples. Untreated patients with MPS I, II, III, VI, and ML had higher levels of HS-0S; and untreated patients with MPS II, III and VI and ML had higher levels of HS-NS. Levels of KS were age dependent, so although levels of both mono-sulfated KS and di-sulfated KS were generally higher in patients, particularly for MPS II and MPS IV, age group numbers were not sufficient to determine significance of such changes. However, the ratio of di-sulfated KS in total KS was significantly higher in all MPS patients younger than 5years old, compared to age-matched controls. MPS I and VI patients treated with HSCT had normal levels of DS, and MPS I, VI, and VII treated with ERT or HSCT had normal levels of HS-0S and HS-NS, indicating that both treatments are effective in decreasing blood GAG levels. CONCLUSION: Measurement of GAG levels in DBS is useful for diagnosis and potentially for monitoring the therapeutic efficacy in MPS.

Glycosaminoglycans detection methods: Applications of mass spectrometry.

Glycosaminoglycans (GAGs) are long blocks of negatively charged polysaccharides. They are one of the major components of the extracellular matrix and play multiple roles in different tissues and organs. The accumulation of undegraded GAGs causes mucopolysaccharidoses (MPS). GAGs are associated with other pathological conditions such as osteoarthritis, inflammation, diabetes mellitus, spinal cord injury, and cancer. The need for further understanding of GAG functions and mechanisms of action boosted the development of qualitative and quantitative (alcian blue, toluidine blue, paper and thin layer chromatography, gas chromatography, high pressure liquid chromatography, capillary electrophoresis, 1,9-dimethylmethylene blue, enzyme linked-immunosorbent assay, mass spectrometry) techniques. The availability of quantitative techniques has facilitated translational research on GAGs into the medical field for: 1) diagnosis, monitoring, and screening for MPS; 2) analysis of GAG synthetic and degradation pathways; and 3) determination of physiological and pathological roles of GAGs. This review provides a history of development of GAG assays and insights about the use of tandem mass spectrometry and its applications for GAG analysis.

Mucopolysaccharidosis IVA and glycosaminoglycans.

Mucopolysaccharidosis IVA (MPS IVA; Morquio A: OMIM 253000) is a lysosomal storage disease with an autosomal recessive trait caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to accumulation of specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS). C6S and KS are mainly produced in the cartilage. Therefore, the undegraded substrates are stored primarily in cartilage and in its extracellular matrix (ECM), leading to a direct impact on cartilage and bone development, and successive systemic skeletal dysplasia. Chondrogenesis, the earliest phase of skeletal formation, is maintained by cellular interactions with the ECM, growth and differentiation factors, signaling pathways, and transcription factors in a temporal-spatial manner. In patients with MPS IVA, the cartilage is disrupted at birth as a consequence of abnormal chondrogenesis and/or endochondral ossification. The unique skeletal features are distinguished by a disproportional short stature, odontoid hypoplasia, spinal cord compression, tracheal obstruction, pectus carinatum, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. In spite of many descriptions of these unique clinical features, delay of diagnosis still happens. The pathogenesis and treatment of systemic skeletal dysplasia in MPS IVA remains an unmet challenge. In this review article, we comprehensively describe historical aspect, property of GAGs, diagnosis, screening, pathogenesis, and current and future therapies of MPS IVA.

Activity of daily living for Morquio A syndrome.

The aim of this study was to evaluate the activity of daily living (ADL) and surgical interventions in patients with mucopolysaccharidosis IVA (MPS IVA). The factor(s) that affect ADL are age, clinical phenotypes, surgical interventions, therapeutic effect, and body mass index. The ADL questionnaire comprises three domains: "Movement," "Movement with cognition," and "Cognition." Each domain has four subcategories rated on a 5-point scale based on the level of assistance. The questionnaire was collected from 145 healthy controls and 82 patients with MPS IVA. The patient cohort consisted of 63 severe and 17 attenuated phenotypes (2 were undefined); 4 patients treated with hematopoietic stem cell transplantation (HSCT), 33 patients treated with enzyme replacement therapy (ERT) for more than a year, and 45 untreated patients. MPS IVA patients show a decline in ADL scores after 10years of age. Patients with a severe phenotype have a lower ADL score than healthy control subjects, and lower scores than patients with an attenuated phenotype in domains of "Movement" and "Movement with cognition." Patients, who underwent HSCT and were followed up for over 10years, had higher ADL scores and fewer surgical interventions than untreated patients. ADL scores for ERT patients (2.5years follow-up on average) were similar with the-age-matched controls below 10years of age, but declined in older patients. Surgical frequency was higher for severe phenotypic patients than attenuated ones. Surgical frequency for patients treated with ERT was not decreased compared to untreated patients. In conclusion, we have shown the utility of the proposed ADL questionnaire and frequency of surgical interventions in patients with MPS IVA to evaluate the clinical severity and therapeutic efficacy compared with age-matched controls.

Hematopoietic stem cell transplantation for Morquio A syndrome.

Morquio A syndrome features systemic skeletal dysplasia. To date, there has been no curative therapy for this skeletal dysplasia. No systemic report on a long-term effect of hematopoietic stem cell transplantation (HSCT) for Morquio A has been described. We conducted HSCT for 4 cases with Morquio A (age at HSCT: 4-15years, mean 10.5years) and followed them at least 10years (range 11-28years; mean 19years). Current age ranged between 25 and 36years of age (mean 29.5years). All cases had a successful full engraftment of allogeneic bone marrow transplantation without serious GVHD. Transplanted bone marrow derived from HLA-identical siblings (three cases) or HLA-identical unrelated donor. The levels of the enzyme activity in the recipient's lymphocytes reached the levels of donors' enzyme activities within two years after HSCT. For the successive over 10years post-BMT, GALNS activity in lymphocytes was maintained at the same level as the donors. Except one case who had osteotomy in both legs one year later post BMT, other three cases had no orthopedic surgical intervention. All cases remained ambulatory, and three of them could walk over 400m. Activity of daily living (ADL) in patients with HSCT was better than untreated patients. The patient who underwent HSCT at four years of age showed the best ADL score. In conclusion, the long-term study of HSCT has demonstrated therapeutic effect in amelioration of progression of the disease in respiratory function, ADL, and biochemical findings, suggesting that HSCT is a therapeutic option for patients with Morquio A.

Current therapies for Morquio A syndrome and their clinical outcomes.

INTRODUCTION: Morquio A syndrome is characterized by a unique skeletal dysplasia, leading to short neck and trunk, pectus carinatum, laxity of joints, kyphoscoliosis, and tracheal obstruction. Cervical spinal cord compression/inability, a restrictive and obstructive airway, and/or bone deformity and imbalance of growth, are life-threatening to Morquio A patients, leading to a high morbidity and mortality. It is critical to review the current therapeutic approaches with respect to their efficacy and limitations. AREAS COVERED: Patients with progressive skeletal dysplasia often need to undergo orthopedic surgical interventions in the first two decades of life. Recently, we have treated four patients with a new surgery to correct progressive tracheal obstruction. Enzyme replacement therapy (ERT) has been approved clinically. Cell-based therapies such as hematopoietic stem cell therapy (HSCT) and gene therapy are typically one-time, permanent treatments for enzyme deficiencies. We report here on four Morquio A patients treated with HSCT approved in Japan and followed for at least ten years after treatment. Gene therapy is under investigation on mouse models but not yet available as a therapeutic option. EXPERT OPINION: ERT and HSCT in combination with surgical intervention(s) are a therapeutic option for Morquio A; however, the approach for bone and cartilage lesion remains an unmet challenge.

Non-invasive pulmonary function test on Morquio patients.

In clinical practice, respiratory function tests are difficult to perform in Morquio syndrome patients due to their characteristic skeletal dysplasia, small body size and lack of cooperation of young patients, where in some cases, conventional spirometry for pulmonary function is too challenging. To establish feasible clinical pulmonary endpoints and determine whether age impacts lung function in Morquio patients non-invasive pulmonary tests and conventional spirometry were evaluated. The non-invasive pulmonary tests: impulse oscillometry system, pneumotachography, and respiratory inductance plethysmography in conjunction with conventional spirometry were evaluated in twenty-two Morquio patients (18 Morquio A and 4 Morquio B) (7 males), ranging from 3 to 40 years of age. Twenty-two patients were compliant with non-invasive tests (100%) with the exception of IOS (81.8%-18 patients). Seventeen patients (77.3%) were compliant with spirometry testing. All subjects had normal vital signs at rest including >95% oxygen saturation, end tidal CO2 (38-44 mmHg), and age-appropriate heart rate (mean=98.3, standard deviation=19) (two patients were deviated). All patients preserved normal values in the impulse oscillometry system, pneumotachography, and respiratory inductance plethysmography, although predicted forced expiratory total (72.8±6.9 SE%) decreased with age and was below normal; phase angle (35.5±16.5°), %rib cage (41.6±12.7%), resonant frequency, and forced expiratory volume in 1 s/forced expiratory volume total (110.0±3.2 SE%) were normal and not significantly impacted by age. The proposed non-invasive pulmonary function tests are able to cover a greater number of patients (young patients and/or wheel-chair bound), thus providing a new diagnostic approach for the assessment of lung function in Morquio syndrome which in many cases may be difficult to evaluate. Morquio patients studied herein demonstrated no clinical or functional signs of restrictive and/or obstructive lung disease.

Impact of enzyme replacement therapy and hematopoietic stem cell transplantation in patients with Morquio A syndrome.

Patients with mucopolysaccharidosis IVA (MPS IVA) can present with systemic skeletal dysplasia, leading to a need for multiple orthopedic surgical procedures, and often become wheelchair bound in their teenage years. Studies on patients with MPS IVA treated by enzyme replacement therapy (ERT) showed a sharp reduction on urinary keratan sulfate, but only modest improvement based on a 6-minute walk test and no significant improvement on a 3-minute climb-up test and lung function test compared with the placebo group, at least in the short-term. Surgical remnants from ERT-treated patients did not show reduction of storage materials in chondrocytes. The impact of ERT on bone lesions in patients with MPS IVA remains limited. ERT seems to be enhanced in a mouse model of MPS IVA by a novel form of the enzyme tagged with a bone-targeting moiety. The tagged enzyme remained in the circulation much longer than untagged native enzyme and was delivered to and retained in bone. Three-month-old MPS IVA mice treated with 23 weekly infusions of tagged enzyme showed marked clearance of the storage materials in bone, bone marrow, and heart valves. When treatment was initiated at birth, reduction of storage materials in tissues was even greater. These findings indicate that specific targeting of the enzyme to bone at an early stage may improve efficacy of ERT for MPS IVA. Recombinant N-acetylgalactosamine-6-sulfate sulfatase (GALNS) in Escherichia coli BL21 (DE3) (erGALNS) and in the methylotrophic yeast Pichia pastoris (prGALNS) has been produced as an alternative to the conventional production in Chinese hamster ovary cells. Recombinant GALNS produced in microorganisms may help to reduce the high cost of ERT and the introduction of modifications to enhance targeting. Although only a limited number of patients with MPS IVA have been treated with hematopoietic stem cell transplantation (HSCT), beneficial effects have been reported. A wheelchair-bound patient with a severe form of MPS IVA was treated with HSCT at 15 years of age and followed up for 10 years. Radiographs showed that the figures of major and minor trochanter appeared. Loud snoring and apnea disappeared. In all, 1 year after bone marrow transplantation, bone mineral density at L2-L4 was increased from 0.372 g/cm(2) to 0.548 g/cm(2) and was maintained at a level of 0.48±0.054 for the following 9 years. Pulmonary vital capacity increased approximately 20% from a baseline of 1.08 L to around 1.31 L over the first 2 years and was maintained thereafter. Activity of daily living was improved similar to the normal control group. After bilateral osteotomies, a patient can walk over 400 m using hip-knee-ankle-foot orthoses. This long-term observation of a patient shows that this treatment can produce clinical improvements although bone deformity remained unchanged. In conclusion, ERT is a therapeutic option for MPS IVA patients, and there are some indications that HSCT may be an alternative to treat this disease. However, as neither seems to be a curative therapy, at least for the skeletal dysplasia in MPS IVA patients, new approaches are investigated to enhance efficacy and reduce costs to benefit MPS IVA patients.

Molecular Genetics and Metabolism Report Long-term follow-up of post hematopoietic stem cell transplantation for Hurler syndrome: clinical, biochemical, and pathological improvements.

Mucopolysaccharidosis type I (MPS I; Hurler Syndrome) is a lysosomal storage disease caused by a deficiency of the enzyme α-L-iduronidase which affects multiple organs such as central nervous system (CNS), skeletal system, and physical appearance. Hematopoietic stem cell transplantation (HSCT) is recommended as a primary therapeutic option at an early stage of MPS I with a severe form to ameliorate CNS involvement; however, no description of pathological improvement in skeletal dysplasia has been investigated to date. We here report a 15-year-old male case with MPS I post-HSCT. This patient received successful HSCT at the age of 2 years and 1 month, followed for over 10 years. His activity of daily living including cognitive performance has been kept normal and the present height and weight are 162 cm and 55 kg. Bone deformity has been still developed, resulting in hemiepiphysiodesis of bilateral medial proximal tibia at 12 years of age and successive arthrodesis of thoraco-lumbar spine at 13 years of age; however, skeletal histopathology from surgical remnants showed substantial improvement in bone lesion with markedly reduced occurrence and cell size of vacuolated cells. After a series of surgical procedures, he became ambulant and independent in daily activity. The levels of GAGs in blood were substantially reduced. In conclusion, this long-term post-HSCT observation should shed light on a new aspect of therapeutic effect associated with skeletal pathology and GAG levels as a biomarker, indicating that HSCT is a primary choice at an early stage for not only CNS but skeletal system in combination of appropriate surgical procedures.