Quantification of arylsulfatase B activity and diagnosis of Maroteaux-Lamy syndrome

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders, each with deficiency of an enzyme degrading glycosaminoglycans (GAG). To increase the ability to differentiate each of the disorders, the N-acetyl-galactosamine-4-sulfatase (arylsulfatase B) activity was measured in human peripheral leukocytes and skin fibroblasts. The assay employed p-nitrocatechol sulfate as an artificial substrate, and barium salt as an inhibitor to arylsulfatase A. Applying this method, a case of Maroteaux-Lamy syndrome (MPS type VI) was recognized in a six-year-old girl who had cloudy cornea, coarse-appearing face, mucopolysacchariduria, and white cell metachromasia. Her body height and mentality were normal. Arylsulfatase B activity in her skin fibroblasts was around 5% of normal. Diagnosis of MPS VI, especially in its milder form, depends on enzyme test.