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

Louise Lapagesse de Camargo Pinto1, Sharbel Weidner Maluf, Sandra Leistner-Segal

  • 1UFRGS, Porto Alegre, Brazil. loulapagesse@ibest.com.br

American Journal of Medical Genetics. Part A
|January 5, 2011
PubMed

Insights

Heterozygous females for mucopolysaccharidosis type II (MPS II) do not show subtle clinical signs of the disease. Enzyme activity was lower in heterozygotes, but this did not correlate with clinical manifestations.

Area of Science:

  • Biochemistry
  • Genetics
  • Rare Diseases

Background:

  • Mucopolysaccharidosis type II (MPS II) is an X-linked disorder.
  • Subtle signs and symptoms in female heterozygotes for MPS II have not been previously studied.
  • Understanding carrier status is crucial for genetic counseling and disease management.

Purpose of the Study:

  • To investigate potential subtle clinical manifestations of MPS II in heterozygotes.
  • To compare clinical and biochemical parameters between MPS II heterozygotes and non-heterozygotes.
  • To determine if X-inactivation patterns influence disease expression in female carriers.

Main Methods:

  • Observational, transversal study of 40 Brazilian women with a family history of MPS II.
  • Data collection included clinical exams, karyotyping, X-inactivation analysis, iduronate-2-sulfatase (IDS) enzyme activity assays, and imaging (CT, MRI).
  • Statistical analysis, including Bonferroni's correction, was used to compare groups.

Main Results:

  • 22 women were identified as heterozygotes and 18 as non-heterozygotes.
  • No significant differences were found in physical exams, karyotypes, or spine CT scans between groups.
  • Lower IDS activity in plasma and leukocytes was observed in heterozygotes, but no clinical abnormalities were detected.

Conclusions:

  • This study found no evidence of subtle clinical manifestations of MPS II in heterozygotes.
  • The findings suggest that reduced IDS activity in heterozygotes does not lead to detectable clinical signs.
  • There appears to be no direct relationship between clinical signs and X-inactivation patterns in these female carriers.

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