Dataset Information

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

ABSTRACT: Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder resulting from pathogenic variants in the ?-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.

SUBMITTER: Clarke LA

PROVIDER: S-EPMC6852151 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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

Clarke Lorne A LA Giugliani Roberto R Guffon Nathalie N Jones Simon A SA Keenan Hillary A HA Munoz-Rojas Maria V MV Okuyama Torayuki T Viskochil David D Whitley Chester B CB Wijburg Frits A FA Muenzer Joseph J

Clinical genetics 20190702 4

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. Un ...[more]

PMID: 31194252

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Project description:BACKGROUND:Serious cardiac valve disease and left ventricular hypertrophy occur in most untreated older children with severe mucopolysaccharidosis type I. Although it is assumed that early intervention prevents these processes, evaluation of cardiac findings in these infants has not yet been reported. METHODS:We reviewed echocardiograms of 13 untreated infants < 1 year of age with severe mucopolysaccharidosis type I who had undergone evaluation for hematopoietic cell transplantation. We recorded left ventricular chamber dimensions, septal and posterior wall thicknesses, ventricular function, and aortic sinus diameters. We evaluated mitral and aortic valves for increased thickness, regurgitation, and stenosis. RESULTS:Average age (7M, 6F) was 221 (range 25-347) days. Left ventricular chamber dimension was ?2 SD of normal in 3/13; wall thicknesses were ?2 SD of normal in 2/13 infants. Systolic function was normal. Mitral valves were thickened in all infants; mitral regurgitation was present in 9/13, but significant in only three infants. Aortic valves were thickened in 10/13, but no infant had significant aortic regurgitation. Neither mitral nor aortic stenosis occurred. Aortic roots were dilated to ?2 SD of normal in 5/13. CONCLUSIONS:Characteristic cardiac features of severe mucopolysaccharidosis type I can be seen in infancy. Mitral and aortic valve thickening are nearly universally present, even in the youngest infants. In 20-30 % of infants, other abnormalities such as left ventricular dilation, increased wall thickness, and mild mitral/aortic regurgitation may occur. Aortic root dilation is a frequent finding. Early intervention with enzyme replacement therapy may minimize the incidence and severity of cardiac findings in these infants. SUMMARY:Serious cardiac valve disease and left ventricular hypertrophy occur in most untreated older children with severe mucopolysaccharidosis type I. Although it is assumed that early intervention prevents these processes, evaluation of cardiac findings in these infants has not yet been reported. In our study of 13 infants with severe untreated MPS I < 1 year of age, mitral and aortic valve thickening was nearly universally present and aortic root dilation was frequent. Despite this, we found a lower incidence of left ventricular hypertrophy and both a lower incidence and milder expression of mitral and aortic valve dysfunction than previously reported in older children. These findings suggest that earlier intervention, including neonatal screening, may be of benefit to children with severe MPS I.

Project description:BackgroundIdursulfase 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.ResultsTwo 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.ConclusionRapid 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.

Dataset Information

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

Publications

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

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