Amniotic fluid glycosaminoglycans in the prenatal diagnosis of mucopolysaccharidoses - A useful biomarker

• Glycosaminoglycans of amniotic fluid consist of hyluronic acid and chondroitin sulphate.
• High concentrations of glycoproteins are excreted in fetus affected with MPS.
• The study established normative data for MPS at 16-22 weeks gestation.
• It is a useful screening test in advanced pregnancies for a quick recognition of MPS.

BackgroundAmniotic fluid glycosaminoglycan estimation is a useful marker in fetuses affected with mucopolysaccharidoses (MPS). Although known for long, it is not widely used in the prenatal diagnosis. With the availability of more reliable analytical testing and knowledge of normal levels at specific gestations, amniotic fluid glycosaminoglycan at 16–22 weeks of gestation can be a useful biomarker in the prenatal diagnosis of MPS.MethodsForty-one women with normal pregnancies were tested for glycosaminoglycan levels in the amniotic fluid and 8 pregnancies with known family history of MPS were tested by sulphated glycosaminoglycan assay.ResultsWe established the amniotic fluid glycosaminoglycan levels in normal pregnancies between 16–22 weeks gestation in Indian women. The mean glycosaminoglycan levels were 16.1 ± 8.7 μg/ml. Out of 8 pregnancies with a positive family history of MPS, 2 showed elevated glycosaminoglycans in the amniotic fluid (220 and 410 μg/ml). The lysosomal enzyme assays, i.e., iduronate-2-sulphate sulphatase and β-glucuronidase in these 2 confirmed the diagnosis of MPS II and MPS VII, respectively. In the remaining 6 pregnancies, both glycosaminoglycan levels and enzyme assays were normal.ConclusionsGlycosaminoglycans are excreted into amniotic fluid by the fetal kidneys and could be used as a marker in the prenatal diagnosis of Mucopolysaccharidoses. This is a useful, fast and cost-effective diagnostic tool in the prenatal diagnosis of mucopolysaccharidoses.