A. H. Fensom

4-methylumbelliferyl α-N-acetylglucosaminidase activity for diagnosis of Sanfilippo B disease

Conditions for assay of a‐JV‐acetylglucosaminidase activity in human cultured fibroblasts, cultured amniotic fluid cells, leucocytes, serum, plasma and chorionic villi were studied using the fluorogenic substrate 4‐methylumbelliferyl‐2‐acetamido‐2‐deoxy‐a‐D‐glucopyranoside. The substrate was found to have advantage both in terms of sensitivity and ease of use over previously‐used colorimetric substrates for assay of the enzyme in these tissues, and for diagnosis of Sanfilippo B disease and identification of carriers. It should have particular application in first trimester prenatal diagnosis using chorionic villus biopsies.

Multiple sulphatase deficiency presenting at birth

A new case of multiple sulphatase deficiency with onset at birth is described. The patient had many dysmorphic features and hydrocephalus, similar to one other case with early onset described in the literature. The new patient differed from the other case in having chondrocalci‐ficans congenita, heart abnormalities and an abnormal fold of tissue present between the laryngeal inlet and the oesophagus. Excessive mucopolysacchariduria was present and there was profound deficiency of all sulphatases examined in plasma, leucocytes and cultured skin fibroblasts.

Progressive mental regression in siblings with Morquio disease Type B (mucopolysaccharidosis IV B)

A brother and sister with clinical and radiological features of Morquio disease, but with atypical mental regression, are described. Leucocyte and fibroblast β‐galactosidase activity was deficient in the siblings, while N‐acetylgalactosamine 6‐sulphate sulphatase and neuraminidase were normal. Study of the residual fibroblast β‐galactosidase activity towards 4‐methylumbelli‐feryl and p‐nitrophenyl β‐D‐galactosides indicated that the mutation resembles that in typical Morquio B disease (increased Km and similar pH maximum) rather than that in GM1‐gangliosidosis. The patients have therefore been classified as having Morquio B disease with atypical mental regression rather than GM1‐gangliosidosis variants with particularly severe bony abnormalities. The mutation was, however, distinct from that in Morquio B disease since residual activity towards the alternative artificial substrate 4‐methylumbelliferyl‐β‐D‐fucoside was increased. The patients represent further examples of the heterogeneity that can result from mutation at the β‐galactosidase locus.

The arylsulphatases of chorionic villi: potential problems in the first-trimester diagnosis of metachromatic leucodystrophy and Maroteaux-Lamy disease

Three pregnancies at risk for late infantile metachromatic leucodystrophy have been monitored using chorionic villus biopsies. In the first of these a false negative diagnosis was made following assay of arylsulphatase A in villi. Subsequent studies have shown that this error was probably due to interference from another sulphatase in the villi, although the possibility that maternal contamination was also partly responsible could not be excluded. For reliable prenatal diagnosis of metachromatic leucodystrophy using chorionic villi it is advisable that studies with the nitrocatechol substrate are carried out on fractionated homogenates, or that the natural substrate is used. Problems may also occur when chorionic villi are used for assay of arylsulphatase B for first trimester diagnosis of Maroteaux‐Lamy disease.

A rapid method for assay of branched-chain keto acid decarboxylation in cultured cells and its application to prenatal diagnosis of maple syrup urine disease.

A sensitive assay for measurement of branched-chain keto acid decarboxylation in small numbers of fibroblasts or amniotic cells grown in the wells of a microtitre plate using [1-14C]leucine as substrate is described. The method was applied to the amniotic cells from a pregnancy at risk for maple syrup urine disease and a heterozygous fetus predicted.

A mild form of mucolipidosis type III in four Baluch siblings

Ward C, Singh R, Slade C, Fensom AH, Fahmy A, Semrin A, Sjövall A, Talat A, Hasilik A, Klein I, Benson PF. A mild form of mucolipidosis type III in four Baluch siblings.

First-trimester diagnosis of metachromatic leucodystrophy

Two pregnancies at risk for late infantile metachromatic leucodystrophy were monitored by assaying arylsulphatase A at 0°C in homogenates of chorionic villi. In one, the very low activity recorded indicated the fetus to be affected, and this was confirmed by demonstration of low arylsulphatase A activity in cultured villi and cultured fetal fibroblasts after termination. In the other pregnancy, normal activity was found in the villi and the pregnancy is continuing. This simple chromogenic assay appears to be reliable for first‐trimester diagnosis of metachromatic leucodystrophy. However, there is a probability of mis‐diagnosis if the standard assay at 37°C is used.

Lumbar kyphosis in Hunter's disease (MPS II)

Although radiological involvement of the lower dorsal and upper lumbar vertebrae is common in the severe form of Hunters disease (MPS II), there are reports in the literature that clinical kyphosis does not occur. We report a boy with marked clinical kyphosis in whom the diagnosis of MPS II was proved by demonstrating a severe deficiency of serum and leucocyte iduronate‐sulphate sulphatase and an accelerated incorporation of radiosulphate into his cultured fibroblast glycosaminoglycans, which could not be corrected by the product of other typed reference MPS II cells. The existence of several other genetic diseases, sometimes complicated by kyphosis, was excluded by assay of fibroblast lysosomal enzymes.

Prenatal diagnosis of galactosaemia in six pregnancies -- possible complications with rare alleles of the galactose 1-phosphate uridyl transferase locus.

We describe our experience in prenatal diagnosis of six foetuses at risk for galactosaemia. In one family the parents were both shown to be double heterozygotes at the galactose 1‐phosphate uridyl transferase (Gal‐PUT) locus, the mother having a Duarte Suppl.Los Angeles and the father a Duarte Suppl.galactosaemia genotype. The foetus (and an older brother previously thought to have classical galactosaemia) was also a Duarte/galactosaemia double heterozygote. In the other five families, the parents and three foetuses were heterozygous carriers of the galactosaemia gene, one of the foetuses had galactosaemia, and one was homozygous for the normal gene. It is concluded that by a combination of family studies and assay of cultured amniotic cell Gal‐PUT, accurate prediction of the foetal Gal‐PUT genotype is now possible.