Functional characterization of arylsulfatase B mutations in Indian patients with Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI)

Twenty years of Colombian experience with enzymatic screening in patients with features of mucopolysaccharidosis

Mucopolysaccharidoses (MPSs) are a group of genetic alterations whose effect is the progressive intralysosomal accumulation of glycosaminoglycans. Affected individuals are deficient in one or more lysosomal enzymes which, depending on the MPS, may cause coarse facial features, short stature, multiple skeletal dysplasia, joint stiffness, or developmental delay. Their diagnosis is mostly performed late or incorrectly, and it represents a challenge since it requires specialized tests only performed in major cities. This makes it difficult for patients to have access to physicians since their geographical location is distant and therefore, the use of samples collected in solid‐phase represents an advantage for the study of high‐risk populations. In addition, epidemiological information about rare diseases, especially in Latin America, is scarce or inconsistent. Our aim was to report the experience of 20 years of selective screening by assessing enzyme activity and reporting incidence values of MPS in Colombia. This study validated a group of fluorometric endpoint techniques in 8239 patients. The samples were dried blood spots (DBS) collected on filter paper and leukocyte extracts. Reference values in the Colombian population for α‐l‐iduronidase, iduronate 2‐sulfatase, α‐N‐acetylglucosaminidase, N‐acetylglucosamine‐6‐sulfate sulfatase, β‐galactosidase, arylsulfatase B, and β‐glucuronidase were established in leukocyte extracts, and patients reference ranges were updated in the case of DBS samples. Incidence values were calculated for each MPS and the distribution of cases across the country is also shown. This study offers very useful information for the health system, the scientific community, and it facilitates the diagnosis of these disorders. This is indispensable when seeking to develop new diagnostic or treatment approaches for patients.

Mapping of IDUA gene variants in Pakistani patients with mucopolysaccharidosis type 1

Background Mucopolysaccharidosis type 1 (MPS1) is a rare debilitating multisystem lysosomal disorder resulting due to the deficiency of α-L-iduronidase enzyme (IDUA), caused by recessive mutations in the IDUA gene. Lack or improper amount of the IDUA enzyme results in the improper metabolism of mucopolysaccharides or glycosaminoglycans (GAGs). These large sugar molecules accumulate in lysosomes within cells leading to different systemic complications. The estimated global incidence of MPS1 is 1:100,000 live births for the Hurler and 1:800,000 for the Scheie phenotypes. Methods Thirteen MPS1-affected children from 12 unrelated cohorts were enrolled. All coding and flanking regions of the IDUA gene were sequenced. Bioinformatics tools were used for data analysis and protein prediction for clinical correlations. Results Six IDUA gene mutations were mapped co-segregating with the recessive pattern of inheritance including a novel variant. A novel missense variant c.908T > C (p.L303P) was mapped in two affected siblings in a cohort in the homozygous form. The variant c.1469T > C (p.L490P) was mapped in five unrelated patients and c.784delC (p.H262Tfs*55) was mapped in three unrelated patients, while mutations c.1598C > G (p.P533R), c.314G > A (p.R105Q) and c.1277ins9 (p.[A394-L395-L396]) were mapped in a single patient each. Conclusions Multisystem disorders and a wide range of clinical presentation impede the evaluation of patients as well as make it difficult to differentiate between different phenotypes of MPS. Early and accurate diagnosis is crucial for the disease management and implementation of an expanded new-born genetic screening program for inborn errors of metabolism including MPS1. We recommend c.784delC (p.H262Tfs*55) and c.1469T > C (p.L490P) as first-line genetic markers for the molecular diagnosis of MPS1 in Pakistan.

Genotypic-phenotypic features and enzyme replacement therapy outcome in patients with mucopolysaccharidosis VI from Turkey

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disorder (LSD) characterized by a chronic, progressive course with multiorgan involvement. In our study, clinical, biochemical, molecular findings, and response to enzyme replacement therapy (ERT) for at least 6 months were evaluated in 20 patients with MPS VI. Treatment effects on clinical findings such as liver and spleen sizes, cardiac and respiratory parameters, visual and auditory changes, joints' range of motions, endurance tests and changes in urinary glycosaminoglycan excretions, before and after ERT were analyzed. ERT caused increased physical endurance and decreased urinary dermatan sulfate/chondroitin sulfate ratios. Changes in growth parameters, cardiac, respiratory, visual, auditory findings, and joint mobility were not significant. All patients and parents reported out an increased quality of life, which were not correlated with clinical results. The most prevalent mutation was p.L321P, accounting for 58.8% of the mutant alleles and two novel mutations (p.G79E and p.E390 K) were found. ERT was a safe but expensive treatment for MPS VI, with mild benefits in severely affected patients. Early treatment with ERT is mandatory before many organs and systems are involved.