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ORIGINAL ARTICLE
Korean J Pediatr 2012 March;55(3) :88-92.
doi:https://doi.org/10.3345/kjp.2012.55.3.88
A study of the relationship between clinical phenotypes and plasma iduronate-2-sulfatase enzyme activities in Hunter syndrome patients
Ok Jeong Lee (Lee OJ)1, Su-Jin Kim (Kim SJ)2, Young Bae Sohn (Sohn YB)1, Hyung-Doo Park (Park HD)3, Soo-Youn Lee (Lee SY)3, Chi-Hwa Kim (Kim CH)4, Ah-Ra Ko (Ko AR)4, Yeon-Joo Yook (Yook YJ)4, Su-Jin Lee (Lee SJ)4, Sung Won Park (Park SW)1, Se-Hwa Kim (Kim SH)1, Sung-Yoon Cho (Cho SY)1, Eun-kyung Kwon (Kwon Ek)1, Sun Ju Han (Han SJ)1, Dong-kyu Jin (Jin Dk)1
1Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
2Center of Pediatric Oncology, National Cancer Center, Goyang, Korea
3Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
4Clinical Research Center, Samsung Biomedical Research Institute, Seoul, Korea
Corresponding Author: Dong-kyu Jin ,Tel: +82-2-3410-3525, Fax: +82-2-3410-0043, Email: jindk@skku.edu
Copyright © 2012 by The Korean Pediatric Society
ABSTRACT
Purpose : Mucopolysaccharidosis type II (MPS II or Hunter syndrome) is a rare lysosomal storage disorder caused by iduronate-2-sulfatase (IDS) deficiency. MPS II causes a wide phenotypic spectrum of symptoms ranging from mild to severe. IDS activity, which is measured in leukocyte pellets or fibroblasts, was reported to be related to clinical phenotype by Sukegawa-Hayasaka et al. Measurement of residual plasma IDS activity using a fluorometric assay is simpler than conventional measurements using skin fibroblasts or peripheral blood mononuclear cells. This is the first study to describe the relationship between plasma IDS activity and clinical phenotype of MPS II. Methods : We hypothesized that residual plasma IDS activity is related to clinical phenotype. We classified 43 Hunter syndrome patients as having attenuated or severe disease types based on clinical characteristics, especially intellectual and cognitive status. There were 27 patients with the severe type and 16 with the attenuated type. Plasma IDS activity was measured by a fluorometric enzyme assay using 4-methylumbelliferyl- -iduronate 2-sulphate. Results : Plasma IDS activity in patients with the severe type was significantly lower than that in patients with the attenuated type (P=0.006). The optimal cut-off value of plasma IDS activity for distinguishing the severe type from the attenuated type was 0.63 nmol·4 hr-1·mL-1. This value had 88.2% sensitivity, 65.4% specificity, and an area under receiver-operator characteristics (ROC) curve of 0.768 (ROC curve analysis; P=0.003). Conclusion : These results show that the mild phenotype may be related to residual lysosomal enzyme activity.
Keywords: Hunter syndrome | Mucopolysaccharidosis II | Iduronate sulfatase | Genotype phenotype
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