Novel approach to idursulfase and laronidase desensitization in type 2 and type 1 S mucopolysaccharidosis (MPS)

BACKGROUND

Idursulfase and laronidase are drugs used to treat Hunter syndrome (mucopolysaccharidosis type 2) and Scheie syndrome (mucopolysaccharidosis type 1 S), respectively. These are rare lysosomal storage disorders, leading to accumulation of glycosaminoglycans within lysosomes. Failure of early recognition of the disease and/or delay in starting the appropriate treatment result in severe clinical impairment and death. For almost 20 years, enzyme replacement therapy with recombinant proteins has represented the first line therapeutic option. However, administration of idursulfase and laronidase is associated with infusion-related hypersensitivity reactions, in approx. 20% of patients. In these patients, rapid desensitization by intravenous administration protocols has been used in order to avoid treatment discontinuation. This approach proved effective and safe. However, long-term tolerance could not be achieved. Thus, we decided to combine rapid desensitization with allergen immunotherapy-like desensitization.

RESULTS

Two patients with Hunter syndrome and one patient with Scheie syndrome developed severe allergy to idursulfase and laronidase, respectively, preventing them from continuing the otherwise indispensable therapy. In all three patients, the possible IgE-mediated nature of the reactions suffered was suggested by positive skin tests with the two enzymes, respectively. By devising 12-step, 3-dilution rapid desensitization protocols, we resumed the enzyme replacement therapy. However, the prolonged time required for administration (a not negligible pitfall, since therapy should be given weekly for life) and the persistent occurrence of reactions (mild but still requiring anti-allergic medication at full dosage) led us to combine rapid desensitization with a compact 11-step, 24-day allergen immunotherapy-like desensitization protocol. Thus, idursulfase and laronidase were injected subcutaneously, with a 500-fold increase from step 1 to step 11 for idursulfase and a 222-fold increase for laronidase. This strategy led to restoration of long-term tolerance, allowing weekly intravenous therapy administration under standard conditions, according to the manufacturer instructions, in the absence of side effects and with only precautionary low-dose premedication.

CONCLUSION

Rapid desensitization is a suitable and safe option in the case of idursulfase and laronidase allergy. Combination with subcutaneous allergen immunotherapy-like desensitization afforded restoration of enzyme replacement therapy given by the normal administration schedule, by inducing sustained tolerance.

In Vivo Confocal Microscopy and Anterior Segment Optical Coherence Tomography Findings in Two Cases with Mucopolysaccharidoses

The mucopolysaccharidoses are a group of disorders caused by inherited defects in lysosomal enzymes resulting in widespread intracellular and extracellular accumulation of glycosaminoglycans. Due to the mucopolysaccharidoses subtype, glycosaminoglycans can be deposited in many organs and tissues including cornea. In this report, we presented in vivo confocal microscopy and anterior segment optical coherence tomography findings in a 39-year old man with Scheie syndrome and a 41-year old woman with Morquio syndrome (Heidelberg Retina Tomograph 3 Rostock module, Germany) and reviewed the literature. On in vivo confocal microscopy, there were multiple small and larger hyperreflective deposits in the epithelium, Bowman layer and anterior stroma and abnormally shaped, elongated keratocytes with hyporeflective round structures, which might be vacuoles in the anterior-mid stroma. In anterior segment optical coherence tomography images, accumulation of glycosaminoglycans deposits lead to an increased hypereflective appearance throughout the thickened cornea.

Cardiac manifestations and effects of enzyme replacement therapy for over 10 years in adults with the attenuated form of mucopolysaccharidosis type I

Background

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disease caused by a deficiency of the lysosomal enzyme α-L-iduronidase. Cardiac manifestations such as valvular heart disease are associated with poor prognosis. There have been only a few reports on the effect of long-term enzyme replacement therapy (ERT) for adult patients with the attenuated form of MPS I (Scheie syndrome) and cardiac involvement.

Methods

We retrospectively reviewed four adult patients of Scheie syndrome for which ERT was performed in our hospital. We investigated the findings of electrocardiography and echocardiography for the four patients performed before and 10 years after the initiation of ERT to evaluate the efficacy for ERT in Scheie syndrome.

Results

The ages of the patients at the initiation of ERT ranged from 26 to 46 years. The mean follow-up period was 129 months (121 to 134 months). Two patients underwent valve replacement surgery before the initiation of ERT. One patient had gradual progressive aortic valve stenosis and mitral valve stenosis during the course of ERT, and double valve replacement was finally performed. The patient who had started ERT at the youngest age did not develop significant cardiovascular disease. Regarding clinical courses with ERT for a period of 10 years, all four patients survived and they showed relatively stable cardiac conditions although two patients developed sick sinus syndrome after the valvular surgery.

Conclusions

Valvular disease in patients with Scheie syndrome occur at a young age. In a limited number of the four patients, ERT might contribute the stability of cardiac condition.

Mucopolysaccharidosis Type I

Mucopolysaccharidosis type I (MPS I) is caused by the deficiency of α-l-iduronidase, leading to the storage of dermatan and heparan sulfate. There is a broad phenotypical spectrum with the presence or absence of neurological impairment. The classical form is known as Hurler syndrome, the intermediate form as Hurler-Scheie, and the most attenuated form is known as Scheie syndrome. Phenotype seems to be largely influenced by genotype. Patients usually develop several somatic symptoms such as abdominal hernias, extensive dermal melanocytosis, thoracolumbar kyphosis odontoid dysplasia, arthropathy, coxa valga and genu valgum, coarse facial features, respiratory and cardiac impairment. The diagnosis is based on the quantification of α-l-iduronidase coupled with glycosaminoglycan analysis and gene sequencing. Guidelines for treatment recommend hematopoietic stem cell transplantation for young Hurler patients (usually at less than 30 months of age). Intravenous enzyme replacement is approved and is the standard of care for attenuated-Hurler-Scheie and Scheie-forms (without cognitive impairment) and for the late-diagnosed severe-Hurler-cases. Intrathecal enzyme replacement therapy is under evaluation, but it seems to be safe and effective. Other therapeutic approaches such as gene therapy, gene editing, stop codon read through, and therapy with small molecules are under development. Newborn screening is now allowing the early identification of MPS I patients, who can then be treated within their first days of life, potentially leading to a dramatic change in the disease's progression. Supportive care is very important to improve quality of life and might include several surgeries throughout the life course.

Genotype-phenotype relationships in mucopolysaccharidosis type I (MPS I): Insights from the International MPS I Registry

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder resulting from pathogenic variants in the α-L-iduronidase (IDUA) gene. Clinical phenotypes range from severe (Hurler syndrome) to attenuated (Hurler-Scheie and Scheie syndromes) and vary in age of onset, severity, and rate of progression. Defining the phenotype at diagnosis is essential for disease management. To date, no systematic analysis of genotype-phenotype correlation in large MPS I cohorts have been performed. Understanding genotype-phenotype is critical now that newborn screening for MPS I is being implemented. Data from 538 patients from the MPS I Registry (380 severe, 158 attenuated) who had 2 IDUA alleles identified were examined. In the 1076 alleles identified, 148 pathogenic variants were reported; of those, 75 were unique. Of the 538 genotypes, 147 (27%) were unique; 40% of patients with attenuated and 22% of patients with severe MPS I had unique genotypes. About 67.6% of severe patients had genotypes where both variants identified are predicted to severely disrupt protein/gene function and 96.1% of attenuated patients had at least one missense or intronic variant. This dataset illustrates a close genotype/phenotype correlation in MPS I but the presence of unique IDUA missense variants remains a challenge for disease prediction.

Arthropathy-like findings and a carpal tunnel syndrome as the presenting features of Scheie syndrome: Three cases from the same family

Gökay S, Kardaş F, Kendirci M, Sözeri B. Arthropathy-like findings and a carpal tunnel syndrome as the presenting features of Scheie syndrome: Three cases from the same family. Turk J Pediatr 2018; 60: 344-347. Mucopolysaccharidosis (MPS) type I is a rare autosomal recessive disease caused by a deficiency of the lysosomal enzyme α-L-iduronidase. MPS I is divided into three subtypes based on the severity of symptoms: Hurler, Hurler-Scheie, and Scheie syndrome (severe, intermediate, and mild forms, respectively). Musculoskeletal involvement may be the only presenting sign in the patients with Scheie syndrome. We have reviewed three cases with prominent features of carpal tunnel syndrome (CTS) at the onset of their disease. Diagnosis was delayed in almost all cases (range 16-19 years). During one year of follow-up period, alleviations of the pain in the hands of patients were observed after enzyme replacement therapy. MPS type I should be considered in the differential diagnosis of the patients with CTS in the first and second decades of life, particularly with stiffness of the fingers and difficulty using the hands without an inflammatory component. An increased awareness of the disease may contribute to more accurate diagnosis, and patients may benefit from early intervention.

Mucopolysaccharidoses: overview of neuroimaging manifestations

The mucopolysaccharidoses are a heterogeneous group of inherited lysosomal storage disorders, characterized by the accumulation of undegraded glycosaminoglycans in various organs, leading to tissue damage. Mucopolysaccharidoses include eight individual disorders (IS [Scheie syndrome], IH [Hurler syndrome], II, III, IV, VI, VII and IX). They have autosomal-recessive transmission with the exception of mucopolysaccharidosis II, which is X-linked. Each individual disorder has a wide spectrum of phenotypic variation, depending on the specific mutation, from very mild to very severe. The skeletal and central nervous systems are particularly affected. The typical clinical presentation includes organomegaly, dysostosis multiplex with short trunk dwarfism, mental retardation and developmental delay. In this article, we review the neuroimaging manifestations of the different types of mucopolysaccharidoses including the dysostosis multiplex of the skull and spine as well as the various central nervous system complications. These include white matter injury, enlargement of the perivascular spaces, hydrocephalus, brain atrophy, characteristic enlargement of the subarachnoid spaces as well as compressive myelopathy. The correlation between several of the neuroimaging features and disease severity remains controversial, without well-established imaging biomarkers at this time. Imaging has, however, a crucial role in monitoring disease progression, in particular craniocervical junction stenosis, cord compression and hydrocephalus, because this allows for timely intervention before permanent damage occurs.

A Unique Case of Cervical Myelopathy in an Adult Patient with Scheie Syndrome

Introduction:

Scheie syndrome is an extremely rare systematic disease that represents the most attenuated form of mucopolysaccharidosis Type I disorder. Although associated with a variety of manifestations, Scheie syndrome leading to the development of cervical myelopathyis yet to be reported. Our purpose was to present a unique case of a Scheie syndrome patient, who underwent surgery due to cervical myelopathy, and to discuss the clinical and imaging findings, as well as the challenges and outcomes of surgical treatment.

Case Report:

A 33-year-old man with Scheie syndrome presented with neck and radicular pain, upper extremity weakness, and insecure gait. The workup studies revealedcervical spine stenosis at multiple levels, caused by accumulation of soft tissue, within the cervical spinal canal. D espite the high risks of anesthesia, and the patient’s inherent poor bone quality that could lead to failure of spinal fusion, we decided to proceed with surgery; indeed, decompressive laminectomies combined with C1-7 posterior stabilization led to immediate pain relief. Despite counter advised, the patient returned to sports rather early, and 6months after index procedure neck pain relapsed, while screw breakage and cutout occurred at the level of C7. Consequently, the initial instrumentation was revised and extended at T2 level. At 2years follow-up, the patient remained continuously pain-free and ambulatory.

Conclusion:

Although cervical myelopathy in Scheie syndrome represents an extremely rare entity, it can make a severe impact on patients’ quality of life. If timely managed though, these patients can be offered a significant relief from symptoms. Surgery is rather challenging and treating physicians should be aware of the high risks of anesthesia. Especially spine surgeons should be aware of the nature of the disease, since it may not allow for fusion, causing instrumentation to fail.

p.L18P: a novel IDUA mutation that causes a distinct attenuated phenotype in mucopolysaccharidosis type I patients

Mucopolysaccharidosis type I is a rare autosomal recessive disorder caused by deficiency of α-l-iduronidase (IDUA) which leads to a wide spectrum of clinical severity. Here, we describe the case of four male patients who present the previously undescribed p.L18P mutation. Patient 1 (p.L18P/p.L18P) presents, despite multiple joint contractures, an attenuated phenotype. Patient 2 (p.L18P/p.W402X) was diagnosed at 4 years of age with bone dysplasia, coarse facies, limited mobility, claw hands and underwent bilateral carpal tunnel surgery at 6 years of age. Patients 3 and 4 (both p.L18P/p.L18P) are brothers. Patient 3 was diagnosed at 4 years of age, when presented claw hands, lower limb and shoulder pain, restricted articular movement and bilateral carpal tunnel syndrome. Patient 4 was diagnosed at 17 months of age when presented lower limb pain at night, respiratory allergy and repeated upper airways infections. Bioinformatics analysis indicates that p.L18P mutation reduces the signal peptide to 25 amino acids and alters its secondary structure. In conclusion, we report a new IDUA variant that alters the structure of the signal peptide, which likely impairs transport to lysosomes. Moreover, it leads to a distinct attenuated phenotype with mainly bone and cartilage symptoms, without visceromegalies, heart disease, or cognitive impairment.

Residual α-L-iduronidase activity in fibroblasts of mild to severe Mucopolysaccharidosis type I patients

Three major clinical subgroups are usually distinguished in Mucopolysaccharidosis type I: Hurler (MPS IH, severe presentation), Hurler-Scheie (MPS IH/S, intermediate) and Scheie (MPS IS, mild). To facilitate treatment with hematopoietic stem-cell transplantation, early diagnosis is important for MPS IH patients. Although screening for MPS I in newborns would allow detection at an early age, it may be difficult to predict the phenotype on the basis of the genotype in these infants. Extra diagnostic tools are thus required. Based on the hypothesis that distinct MPS I phenotypes may result from differences in residual α-l-iduronidase (IDUA) activity, we modified the common IDUA assay using the substrate 4-methylumbelliferyl-α-l-iduronide to allow quantification of low IDUA activity in MPS I fibroblasts. Enzyme incubation was performed with high protein concentrations at different time points up to 8h. Mean residual IDUA activity was 0.18% (range 0-0.6) of the control value in MPS IH fibroblasts (n=5); against 0.27% (range 0.2-0.3) in MPS IH/S cells (n=3); and 0.79% (range 0.3-1.8) in MPS IS fibroblasts (n=5). These results suggest that residual IDUA activity and severity of the MPS I phenotype are correlated. Two MPS IS patients with rare (E276K/E276K) or indefinite (A327P/unknown) IDUA genotypes had residual IDUA activity in the MPS IS range, illustrating the usefulness of our approach. IDUA(E276K) was very unstable at 37°C, but more stable at 23°C, suggesting thermal instability. We conclude that this procedure for determining residual IDUA activity in fibroblasts of MPS I patients may be helpful to predict MPS I phenotype.

Laronidase for the treatment of mucopolysaccharidosis type I

A decade has passed since the initial report that parenteral use of recombinant human α-L-iduronidase results in amelioration of symptoms in patients with mucopolysaccharidosis type I (MPS I). As a result, MPS I became the first mucopolysaccharide storage disorder to benefit from enzyme replacement therapy (ERT); subsequent ERTs have been approved for MPS II and VI. The ability of lysosomal storage disorders to respond to ERT is unique among genetic disorders and relates to the capability of cells to take up recombinant lysosomal enzymes through cell surface receptors and deliver them to the lysosome, a processed coined as 'cross-correction'. Although the concept of ERT is straightforward, the evaluation of its efficacy in disorders like MPS I is challenging. This article reviews the use of laronidase in the management of MPS I, with a particular emphasis on the unique issues inherent in the evaluation of therapeutics for such a rare, complex and progressive disorder.