Development of an assay for the detection of mucopolysaccharidosis type VI patients using dried blood-spots

Abstract

<h4>Background</h4>Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disorder (LSD), which is caused by a deficiency in the enzyme N-acetylgalactosamine 4-sulfatase (4-sulfatase). MPS VI is characterized by severe skeletal abnormalities, somatic tissue pathology and early death. Treatment possibilities include bone marrow transplantation (BMT) and enzyme replacement therapy (ERT; currently in phase III clinical trial). Early diagnosis of MPS VI will allow treatment before the onset of irreversible pathology.<h4>Methods</h4>Sensitive immune assays have been developed to detect 4-sulfatase protein and activity in normal control and MPS VI blood-spots.<h4>Results</h4>Dried blood-spots from MPS VI patients contained no detectable 4-sulfatase protein and activity, compared to 3.5-21 microg/L of 4-sulfatase protein and 291-1298 nmol/min/L of activity for normal human controls. In this evaluation study, the assay was sensitive and 100% specific, allowing reliable detection of individuals with MPS VI.<h4>Conclusions</h4>The assays reported here have the potential to detect MPS VI patients using dried blood-spots.