Are MPS II heterozygotes actually asymptomatic? A study based on clinical and biochemical data, X-inactivation analysis and imaging evaluations

• Published in: American journal of medical genetics. Part A 2011-01, Vol.155A (1), p.50-57
• Main Authors: de Camargo Pinto, Louise Lapagesse, Maluf, Sharbel Weidner, Leistner-Segal, Sandra, Zimmer da Silva, Camila, Brusius-Facchin, Ana, Burin, Maira Graef, Brustolin, Silvia, Llerena, Juan, Moraes, Lucia, Vedolin, Leonardo, Schuch, Alice, Giugliani, Roberto, Schwartz, Ida Vanessa Doederlein
• Format: Article
• Language: English
• Subjects: Abdomen; Biological and medical sciences; Brazil; Carbohydrates (enzymatic deficiencies). Glycogenosis; Computed tomography; Data processing; DNA; Errors of metabolism; Female; Glycoproteins - blood; Glycosaminoglycans; Glycosaminoglycans - urine; Heterozygote; Heterozygotes; Humans; iduronate sulfatase; Karyotypes; Karyotyping; Kidney - pathology; Leukocytes; lycosaminoglycans; Magnetic Resonance Imaging; Male; Medical genetics; Medical sciences; Metabolic diseases; Mucopolysaccharidosis; Mucopolysaccharidosis II - genetics; Mucopolysaccharidosis II - pathology; mucopolysaccharidosis type II; Neuroimaging; Spine; Spleen - pathology; Statistics, Nonparametric; Tomography, X-Ray Computed; X chromosome; X Chromosome Inactivation - genetics; X-chromosome inactivation; X-inactivation
• ISSN: 1552-4825; 1552-4833; 1552-4833
• DOI: 10.1002/ajmg.a.33770

For some X‐linked disorders the expressivity and penetrance in females are almost similar to those ones found in males. For mucopolysaccharidosis type II (MPS II), there are no studies in the literature trying to identify subtle signs and symptoms of this disease in heterozygotes. The objective of this study was to compare heterozygotes and non‐heterozygotes for MPS II, in order to test the hypothesis that heterozygotes may present subtle manifestations of the disease. In this observational and transversal study we collected data on 40 Brazilian women with a positive familial history for MPS II that included clinical and physical exam, karyotype, pattern of X‐inactivation, iduronate‐2‐sulfatase (IDS) activity in leukocytes and plasma, urinary glycosaminoglycans levels, computerized tomography scans (CT) of abdomen and spine, and brain magnetic resonance imaging. The Results showed the following: According to DNA analysis, 22 women were classified as heterozygote and 18 as non‐heterozygotes. We did not find any abnormality on physical examination, karyotype, or spine CT. Also the pattern of X‐inactivation was not different between the groups. Applying the Bonferroni's correction, both groups were found to differ only in relation to IDS activity in plasma and in leukocyte, which were lower in heterozygotes. In our investigation we did not find any evidence of subtle clinical manifestations of MPS II in heterozygotes. Our findings suggest there is no relation between the absence of clinical signs in these women and the occurrence of a favorable skewing pattern of X‐inactivation. © 2010 Wiley‐Liss, Inc.