Lowβ‐glucuronidase activity in a healthy member of a family with mucopolysaccharidosis VII

Abstract

A phenotypically normal mother of a mucopolysaccharidosis VII child, is reported with an unusually lowβ‐glucuronidase activity. Low enzyme activity was systemic (6–10% of controls) and residualβ‐glucuronidase in leukocytes had an apparently normalK_m value. [³⁵S]sulphate incorporation and chase assays in fibroblasts gave values similar to control cells. A normal excretion pattern of glycosaminoglycan was found in this woman's urine. Low enzymatic activity can be related to a non‐pathological ‘pseudodeficiency’ allele forβ‐glucuronidase; this woman appears to be an apparent compound heterozygote for this allele and mucopolysaccharidosis VII. Her next pregnancy was monitored by chorionic villus sampling and a heterozygous fetus was suspected. These studies stress the need for complete enzyme investigations of obligate carriers for mucopolysaccharidoses in order to prevent difficulties at prenatal analysis.