G. T. N. Besley

Bile acid analyses in "pseudo-Zellweger" syndrome; clues to the defect in peroxisomal beta-oxidation.

In Zellweger syndrome, β-oxidation of very long chain fatty acids (VLCFA) and C27 bile acids is impaired because peroxisomes are absent (Schutgens et al., 1986). In 1986, Goldfischer et al. described an infant with ‘pseudo-Zellweger’ syndrome in whom peroxisomes were present but oxidation of VLCFA and C27 bile acids impaired, due to a deficiency of peroxisomal 3-oxoacyl-CoA thiolase (Schram et al., 1987). This paper describes three siblings with deficient peroxisomal β-oxidation but structurally normal peroxisomes. Immunoreactive acyl CoA-oxidase, bifunctional protein and thiolase were all present in the liver but analysis of the C27 bile acids suggested a functional deficiency of peroxisomal thiolase (or possibly of the bifunctional protein).

Enzyme activities and phospholipid storage patterns in brain and spleen samples from niemann-pick disease variants: a comparison of neuropathic and non-neuropathic forms

Phospholipid levels and enzyme activities were measured in brain and spleen samples from patients with the three major variants of Niemann-Pick disease. Accumulations of sphingomyelin and bis(monoacylglycero)phosphate were demonstrated in spleen from types A and B and group C Niemann-Pick disease, whereas only in type A Niemann-Pick brain was the sphingomyelin concentration increased. Sphingomyelinase activity was markedly deficient in type A Niemann-Pick brain and spleen but residual activity of approximately 12% of control was measured in type B Niemann-Pick brain. Normal or raised sphingomyelinase and β-glucosidase activities were measured in group C Niemann-Pick brain and spleen. Significant (17% of control) residual β-glucosidase activity was also measured in non-neuropathic Gaucher brain. Normal levels of neutral sphingomyelinase activity were measured in brain samples from the three variants of Niemann-Pick disease. Acid sphingomyelinase activity in group C Niemann-Pick brain appeared normal with respect to enzyme extraction, pH optimum (pH5.0) and apparentKm (approximately 0.4 mmol/L). Isoelectric focusing of brain sphingomyelinase revealed a degree of heterogeneity with activity peaks between pI 4.5 and 6.5. No defect was observed in group C Niemann-Pick brain and, although attenuated, all peaks were present in type B Niemann-Pick brain.

Peroxisomal Enzyme Deficiency in X-linked Dominant Conradi—Hünermann Syndrome

The X-linked dominant Conradi—Hunermann syndrome (CHS-XD, McKusick 30295) is characterized by ichthyosiform erythroderma at birth giving way to whorled areas of hyperkeratosis, streaky follicular atrophoderma, cicatricial alopecia and coarse lustreless hair. The facies typically shows frontal bossing, a flattened nasal bridge and malar hypoplasia. Cataracts are common. Skeletal abnormalities include the transient punctate epiphyseal calcifications, asymmetric limb shortening and short stature. According to Happle (1981), CHS-XD can be readily distinguished from an autosomal dominant form of the Conradi—Hunermann syndrome (CHS-AD, McKusick 11865) because the latter does not produce whorled/streaky skin lesions or cataracts. Differentiation between CHS-XD and autosomal recessive rhizomelic chondrodysplasia punctata (RCP, McKusick 21510) presents no serious problem: patients with RCP have severe, symmetrical proximal limb shortening, marked psychomotor retardation, mild ichthyotic skin changes and they rarely survive beyond 2 years of age.

Phosphorylaseb kinase deficiency in glycogenosis type VIII: Differentiation of different phenotypes and heterozygotes by erythrocyte enzyme assay

Erythrocytes provide a useful sample in which to study phosphorylaseb kinase defects in families affected with GSD VIII.

Hexanol dehydrogenase activity shown by enzyme histochemistry on skin biopsies allows differentiation of Sjögren-Larsson syndrome from other ichthyoses

Ichthyoses are a group of hereditary and acquired disorders in which there are visible scales on the skin surface (Williams, 1983). While there are some clinical differences, the histopathological differentiation of one type of ichthyosis from another is difficult. In most cases there is acanthosis and hyperkeratosis (which may be orthokeratosis or parakeratosis) and the granular layer may be prominent, normal or diminished. Although there are some general guidelines which are intended to aid in the differential diagnosis of the ichthyoses, in practice it is usually impossible to separate Sj6grenLarsson syndrome (SLS; McKusick 27020) from X-linked ichthyosis, ichthyosis vulgaris or non-buttous ichthyosis. SLS is an inherited disorder in which mental retardation and spasticity occur (Sj6gren and Larsson, 1957) and accurate diagnosis is important. Defective fatty alcohol:NAD + oxidoreductase activity has been described in cultured fibroblasts and leukocytes from patients with SLS (Rizzo et al., 1989). We have developed a histochemical method for the demonstration of hexanol dehydrogenase activity using a simple staining method on cryostat sections of skin biopsies, which gives complementary results to the biochemical assay.

FIRST TRIMESTER DIAGNOSIS OF INHERITED METABOLIC DISEASE : EXPERIENCE IN THE UK

SummaryExperience with first trimester diagnosis of inherited metabolic disease is still limited. In this report, data are collected from four major centres in the UK which provide a prenatal diagnosis service based on specific enzyme or gene product assay. The data were presented at a workshop on ‘First Trimester Diagnosis of Inherited Metabolic Disease’ held at the Institute of Child Health, London, on 21st June 1990.Approximately 100 different metabolic diseases can now be diagnosed in the first trimester, but because of the rarity of many of the disorders, experience of positive diagnoses, based on enzyme deficiency in fresh chorionic villus samples (CVS), cultured villus cells or early amniocentesis samples, is likely to be limited. It is, however, important that these results are reported and similarly that any problems which arise are fully documented.

Prenatal Diagnosis of Inherited Metabolic Disease by Chorionic Villus Analysis: The Edinburgh Experience

Prenatal diagnosis of inherited metabolic disease is possible when suitable samples of fetal material are available and when these samples express a clear biochemical abnormality that is specific to that disorder. In the past, tests have been carried out by enzyme assay on cultured amniotic fluid cells and/or analysis of amniotic fluid for metabolites. These tests, carried out late into pregnancy (16 weeks plus), cause much anxiety and added risks to mothers. With the advent of first trimester chorionic villus sampling, tests may now be carried out directly on chorionic villus samples (CVS) with results available in a matter of days (Poenaru, 1987; Sachs et al., 1988). The advantages to those at risk are obvious but like many new techniques specific problems may arise.

The use of natural and artificial substrates in the prenatal diagnosis of Krabbe's disease

Krabbes disease was diagnosed prenatally using cultured amniotic fluid cells and the diagnosis confirmed using fetal brain, liver and cultured fetal skin fibroblasts. The enzyme defect was demonstrated by assay of galactocerebrosidase and lactocerebrosidase I, and by hydrolysis of the chromogenic analogue, 2-hexadecanoylamino-4-nitrophenyl-β-D-galactopyranoside. The relative merits of the three diagnostic methods are discussed.

Dihydroxyacetone Phosphate Acyltransferase Deficiency in Peroxisomal Disorders

There is much current interest in disorders of peroxisomal function and until recently little was known of the biochemical basis of these diseases. In patients such as those with Zellweger syndrome (McKusick 21410) where there is a generalized peroxisomal disturbance, a number of biochemical functions are impaired (Schutgens et al., 1986). Recognition of these defects may assist in diagnosis. These biochemical defects include accumulations of very long chain fatty acids, bile acid intermediates, phytanic acid, pipecolic acid and dicarboxylic acids, all of which appear to be normally oxidized in peroxisomes. Furthermore, there is a reduction in the level of certain plasmalogens (Heymans et al., 1984), the synthesis of which is dependent on two peroxisomal enzymes, acyl-CoA: dihydroxyacetone phosphate acyl transferase (DHAP-AT) and alkyl dihydroxyacetone phosphate synthase. Deficiencies of each of these activities have been reported (Schutgens et al., 1984; Datta et al., 1984) in Zellweger syndrome. Deficiency of DHAP-AT activity has also been reported in infantile Refsum disease and neonatal adrenoleukodystrophy (McKusick 20237) as well as in the rhizomelic form of chondrodysplasia punctata (McKusick 21510) where peroxisomes may be present. In response to the need for a simple but reliable preand postnatal diagnostic test for these disorders, we have studied DHAP-AT activity in cultured fibroblasts, blood thrombocytes and leukocytes from such patients and report our findings here.

Acid Esterase Deficiency: Comparison of Biochemical Findings in Infantile and Adult Forms

A deficiency of lysosomal acid esterase activity in humans usually results in one of two phenotypically distinct storage disorders (Assmann and Fredrickson, 1983). In Wolman’s disease (McKusick 27800) the course is rapid, resulting in death in infancy whereas cholesterol ester storage disease (CESD; McKusick 21500) is relatively benign and patients usually survive well into adulthood. These disorders are relatively rare and few comparative biochemical studies have been reported. In this report, three patients, two with Wolman’s disease and one with CESD, have been studied in an attempt to identify a biochemical basis for their phenotypic expression.