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

BACKGROUND: Amniotic 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 16-22weeks of gestation can be a useful biomarker in the prenatal diagnosis of MPS.

METHODS: Forty-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.

RESULTS: We established the amniotic fluid glycosaminoglycan levels in normal pregnancies between 16-22weeks gestation in Indian women. The mean glycosaminoglycan levels were 16.1±8.7μg/ml. Out of 8 pregnancies with a positive family history of MPS, 2 showed elevated glycosaminoglycans in the amniotic fluid (220 and 410μg/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.

CONCLUSIONS: Glycosaminoglycans 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.