Immediate prenatal diagnosis of Zellweger syndrome by direct measurement of very long chain fatty acids in chorionic villus cells

Zellweger syndrome in Saudi Arabia and its distinct features

Clinical and laboratory findings of Zellweger syndrome (ZS) patients diagnosed at King Faisal Specialist Hospital and Research Center (KFSH & RC), Riyadh, Saudi Arabia over a period of 10 years are presented in this report. Eleven patients (nine females and two males) from 2 to 4 months old were referred to KFSH & RC for evaluation of hypotonia, seizures, and dysmorphic features. The common clinical findings included high forehead, large fontanelle, shallow orbit ridges, micrognathia, upslanting palebral fissures, epicanthal folds, severe hypotonia, hyporeflexia, pigmentary retinopathy, optic nerve atrophy, complete or partial agenesis of corpus callusum, and failure to thrive. We did not observe any Brushfield spots, any renal and brain cysts, or adrenal insufficiency. Some unique clinical findings were the presence of gallstones, club feet, or bilateral knee or hip dislocation in some patients. All patients had markedly elevated plasma levels of very long chain fatty acids (VLCFA). Electron microscopy performed on liver biopsies of two patients revealed absence of peroxisomes. Biochemical studies of dermal fibroblasts from three patients showed deficient beta-oxidation of lignoceric acid and dihydroxyacetone phosphate acyltransferase (DHAPATase) activity. The tribal living in Saudi Arabia and our observation that 10 of the 11 parents in this study were first-degree relatives and, except for families 1 and 3, each family had at least another baby who died of the same disease. This suggests that the incidence of ZS in Saudi Arabia may actually be higher than our experience at KFSH & RC.

Prenatal diagnosis in high risk pregnancies for Zellweger syndrome

Zellweger syndrome is a lethal disorder. At present, no effective therapies are known for the patients of Zellweger syndrome. Recently a typical case of Zellweger syndrome in Japan was observed. In spite of intensive care, the patient died at the age of 3 months. Following this, the parents requested prenatal diagnosis for their following two pregnancies. We investigated levels of very long chain fatty acids (VLCFA), levels of bile acids in amniotic fluid and immunoblotting of peroxisomal beta-oxidation enzymes in cultured amniocytes. We report that immunoblotting using cultured amniocytes is an effective method for prenatal diagnosis of Zellweger syndrome. Furthermore, if we use immunoblotting for prenatal diagnosis, we can discriminate pseudoZellweger syndrome from pseudoneonatal adrenoleucodystrophy. Following prenatal diagnosis, two healthy babies were delivered. After birth, no abnormal levels of VLCFA in either serum or red blood cell membranes were confirmed. In this paper, we report that we can diagnose a healthy fetus in a high risk pregnancy for Zellweger syndrome.

Peroxisomal disorders

Peroxisomal disorders occur more frequently and have a wider range of clinical manifestations than has been realized in the past. Precise diagnosis can be achieved with non-invasive biochemical assays and all can be diagnosed prenatally, thus providing the option of genetic counseling. Specific therapy is being evaluated for one of these disorders (adrenoleukodystrophy). In addition to these clinical advances, a great deal of information has been gained recently about the biogenesis and normal function of peroxisomes. These latter advances have been stimulated, and in part created, by the study of human disease states. It is for these reasons that a review of these human disease states is relevant for the clinical biochemist.

Prenatal diagnosis of inborn errors in peroxisomal beta-oxidation

In recent years, an increasing number of inherited diseases in man have been recognized in which there is an impairment in the peroxisomal beta-oxidation of very-long-chain fatty acids. In general, these disorders are associated with severe neurological and physical abnormalities and death within the first years of life. In this paper we describe our experience with regard to the prenatal diagnosis of a number of different inborn errors of peroxisomal beta-oxidation. Eleven pregnancies at risk were monitored by measuring very-long-chain fatty acid levels as well as very-long-chain fatty acid beta-oxidation in cultured chorionic villous fibroblasts and/or amniotic fluid cells. Five affected fetuses were identified. It is concluded that prenatal diagnosis in this group of diseases can be done reliably using cultured chorionic villous fibroblasts or amniotic fluid cells.

The peroxisome and the eye

Several childhood multisystem disorders with prominent ophthalmological manifestations have been ascribed to the malfunction of the peroxisome, a subcellular organelle. The peroxisomal disorders have been divided into three groups: 1) those that result from defective biogenesis of the peroxisome (Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum's disease); 2) those that result from multiple enzyme deficiencies (rhizomelic chondrodysplasia punctata); and 3) those that result from a single enzyme deficiency (X-linked adrenoleukodystrophy, primary hyperoxaluria type 1). Zellweger syndrome, the most lethal of the three peroxisomal biogenesis disorders, causes infantile hypotonia, seizures, and death within the first year. Ophthalmic manifestations include corneal opacification, cataract, glaucoma, pigmentary retinopathy and optic atrophy. Neonatal adrenoleukodystrophy and infantile Refsum's disease appear to be genetically distinct, but clinically, biochemically, and pathologically similar to Zellweger syndrome, although milder. Rhizomelic chondrodysplasia punctata, a peroxisomal disorder which results from at least two peroxisomal enzyme deficiencies, presents at birth with skeletal abnormalities and patients rarely survive past one year of age. The most prominent ocular manifestation consists of bilateral cataracts. X-linked (childhood) adrenoleukodystrophy, results from a deficiency of a single peroxisomal enzyme, presents in the latter part of the first decade with behavioral, cognitive and visual deterioration. The vision loss results from demyelination of the entire visual pathway, but the outer retina is spared. Primary hyperoxaluria type 1 manifests parafoveal subretinal pigment proliferation. Classical Refsum's disease may also be a peroxisomal disorder, but definitive evidence is lacking. Early identification of these disorders, which may depend on recognizing the ophthalmological findings, is critical for prenatal diagnosis, treatment, and genetic counselling.

The inborn errors of peroxisomal beta-oxidation: a review

In recent years a growing number of inherited diseases in man have been recognized in which there is an impairment in peroxisomal beta-oxidation. In some diseases this is due to the (virtual) absence of peroxisomes leading to a generalized loss of peroxisomal functions including peroxisomal beta-oxidation. In most inborn errors of peroxisomal beta-oxidation, however, peroxisomes are normally present and the impairment in peroxisomal beta-oxidation is due to the single or multiple loss of peroxisomal beta-oxidation enzyme activities. In all these disorders there is accumulation of very-long-chain fatty acids in plasma, which allows biochemical diagnosis of patients affected by an inborn error of peroxisomal beta-oxidation to be done via gas-chromatographic analysis of plasma very-long-chain fatty acids. Subsequent enzymic and immunological investigations are required to identify the precise enzymic defects in these patients. In all inborn errors of peroxisomal beta-oxidation known today there are multiple abnormalities, especially neurological with death usually occurring in the first decade of life. Prenatal diagnosis of these disorders has recently become possible.

Prenatal and perinatal diagnosis of peroxisomal disorders

Peroxisomes play an essential role in human cellular metabolism. Peroxisomal disorders, a group of genetic diseases caused by peroxisomal dysfunction, can be classified into three groups: (1) disorders of peroxisome biogenesis with a generalized loss of peroxisomal functions (Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease, hyperpipecolic acidaemia); (2) disorders with a loss of multiple peroxisomal functions (rhizomelic chondrodysplasia punctata and Zellweger-like syndrome; (3) disorders with loss of a single peroxisomal function (X-linked adrenoleukodystrophy, peroxisomal thiolase deficiency, bifunctional protein deficiency, acyl-CoA oxidase deficiency, classic Refsum disease, hyperoxaluria type I and acatalasaemia). Prenatal diagnosis is indicated in all these genetic disorders with the exception of classic Refsum disease, most types of hyperoxaluria type I and acatalasaemia. A variety of techniques is available now for the prenatal diagnosis of peroxisomal disorders in the first or second trimester of gestation. Prenatal diagnosis was performed by us in 70 pregnancies at risk for a disorder of peroxisome biogenesis, three for rhizomelic chondrodysplasia punctata, four for X-linked adrenoleukodystrophy and two for a defect in peroxisomal beta-oxidation. Fourteen affected fetuses were identified; no false negative cases were obtained.

Peroxisomal disorders in neurology

Although peroxisomes were initially believed to play only a minor role in mammalian metabolism, it is now clear that they catalyse essential reactions in a number of different metabolic pathways and thus play an indispensable role in intermediary metabolism. The metabolic pathways in which peroxisomes are involved include the biosynthesis of ether phospholipids and bile acids, the oxidation of very long chain fatty acids, prostaglandins and unsaturated long chain fatty acids and the catabolism of phytanate and (in man) pipecolate and glyoxylate. The importance of peroxisomes in cellular metabolism is stressed by the existence of a group of inherited diseases, the peroxisomal disorders, caused by an impairment in one or more peroxisomal functions. In the last decade our knowledge about peroxisomes and peroxisomal disorders has progressed enormously and has been the subject of several reviews. New developments include the identification of several additional peroxisomal disorders, the discovery of the primary defect in several of these peroxisomal disorders, the recognition of novel peroxisomal functions and the application of complementation analysis to obtain information on the genetic relationship between the different peroxisomal disorders. The peroxisomal disorders recognized at present comprise 12 different diseases, with neurological involvement in 10 of them. These diseases include: (1) those in which peroxisomes are virtually absent leading to a generalized impairment of peroxisomal functions (the cerebro-hepato-renal syndrome of Zellweger, neonatal adrenoleukodystrophy, infantile Refsum disease and hyperpipecolic acidaemia); (2) those in which peroxisomes are present and several peroxisomal functions are impaired (the rhizomelic form of chondrodysplasia punctata, combined peroxisomal beta-oxidation enzyme protein deficiency); and (3) those in which peroxisomes are present and only a single peroxisomal function is impaired (X-linked adrenoleukodystrophy, peroxisomal thiolase deficiency (pseudo-Zellweger syndrome), acyl-CoA oxidase deficiency (pseudo-neonatal adrenoleukodystrophy) and probably, the classic form of Refsum disease.