A simple DHEAS loading test in the antepartum diagnosis of placental sulphatase deficiency

Steroid sulphatase deficiency: identification of heterozygotes using hydrolysis of dehydroepiandrosterone sulphate by peripheral leucocytes

Diagnosis of X-linked recessive ichthyosis, which is expressed only in males, can readily be made by measurement of leucocyte steroid sulphatase activity. However, because the gene for steroid sulphatase activity partly escapes from the process of X-chromosome inactivation associated with gene dosage compensation, identification of heterozygotes (females) is more difficult. We have measured the steroid sulphatase (by hydrolysis of dehydroepiandrosterone sulphate) and beta-glucuronidase (by hydrolysis of methylumbelliferyl glucuronide) activities in leucocytes from 18 heterozygotes, 100 normal females, 100 normal males and 11 affected subjects. When the ratio of the activities of steroid sulphatase and beta-glucuronidase in mixed leucocytes was plotted as a function of the steroid sulphatase activity, 85% heterozygotes were distinguished from normal females. Measurement of steroid sulphatase activity alone with these cells enabled identification of 78% heterozygotes. Measurements on mononuclear leucocytes were much less effective. Thrombocytes showed 1% of the steroid sulphatase activity of leucocytes. In females, leucocyte steroid sulphatase activity was independent of the stage of the ovarian cycle at which the cells were collected.

Antenatal detection of placental steroid sulphatase deficiency by measurement of urinary 16 alpha-hydroxydehydroepiandrosterone sulphate

A simple gas chromatographic technique for the measurement of 16 alpha-hydroxydehydroepiandrosterone sulphate in urine from pregnant women is described. An assessment was made of the effectiveness of the measurement of this oestriol precursor for the antenatal diagnosis of placental steroid sulphatase deficiency. Twenty-two patients whose pregnancies were complicated by subnormal oestrogen excretion for gestation were studied. In nine of these, where placental steroid sulphatase activity was found subsequently in vitro to be normal, the excretion of 16 alpha-hydroxydehydroepiandrosterone sulphate was less than 27 mumol/24 h. In the remaining 13 patients, in whom postnatal in vitro assay demonstrated absence of placental steroid sulphatase activity, urinary excretion of 16 alpha-hydroxydehydroepiandrosterone sulphate was 59-360 mumol/24 h. The excretion of this metabolite was below the limit of detection (20 mumol/24 h) in 30 uncomplicated pregnancies. It is concluded that urinary excretion of 16 alpha-hydroxydehydroepiandrosterone sulphate greater than 50 mumol/day or a ratio of urinary 16 alpha-hydroxydehydroepiandrosterone sulphate to urinary oestrogen greater than 2.0 correctly identifies, before delivery, those pregnancies in which fetus and placenta are deficient in steroid sulphatase activity.