Rhizomelic chondrodysplasia punctata with isolated DHAP-AT deficiency.

An infant with the characteristic phenotype of classical rhizomelic chondrodysplasia punctata was found to have an isolated deficiency of the peroxisomal enzyme acyl CoA dihydroxyacetone phosphate acyltransferase (DHAP-AT). All other peroxisomal functions measured were found to be normal. Previously described in one other case report, this confirms the existence of another distinct form of peroxisomal disorder characterised biochemically by a deficiency in de novo plasmalogen biosynthesis only.     

Clinical and biochemical characteristics of peroxisomal disorders: an update

Peroxisomal disorders represent a recently recognized group of inherited diseases in man, now comprising 14 different disorders. If discussion is restricted to those peroxisomal disorders in which there is neurological involvement (thereby excluding hyperoxaluria and acatalasaemia), results over the least few years have shown that analysis of very-long-chain fatty acids (VLCFAs) is a highly reliable initial test to establish whether or not one is dealing with a peroxisomal disorder. Rhizomelic chondrodysplasia punctata, its recently identified variant form and glutaryl-CoA oxidase deficiency will show no abnormalities and must be identified by other means. Recently we have found a few clinically proven cases of adrenoleukodystrophy showing normal VLCFA in plasma but clearly abnormal values in fibroblasts. This suggests that great care is warranted in interpreting plasma VLCFA analyses. Furthermore, plasma bile acids, phytanic acid, pristanic acid and pipecolic acid should be analysed in any patient with clinical symptoms suggestive for a peroxisomal disorder but normal plasma VLCFAs.     

Characteristic acylcarnitine profiles in inherited defects of peroxisome biogenesis: a novel tool for screening diagnosis using tandem mass spectrometry

Patients with inherited defects of peroxisomal metabolism, a class of diseases with marked clinical and genetic heterogeneity, show a characteristic phenotype in most cases with severe neurologic impairment, craniofacial abnormalities, and hepatic and kidney dysfunction. For the differential diagnosis of clinically suspected cases, a complex biochemical and genetic approach is required. Analysis of plasma very-long-chain fatty acids is a reliable screening method to detect most but not all peroxisomal disorders. To study the potential presence of abnormal acylcarnitine species in plasma and blood, we screened by tandem mass spectrometry a series of patients affected by a peroxisome biogenesis disorder (PBD) and compared the results with those obtained in patients with isolated peroxisomal defects (e.g. D-bifunctional protein deficiency, X-linked adrenoleukodystrophy) and mitochondrial long-chain fatty acid oxidation defects. The most relevant finding observed in plasma of patients with PBD was a significant increase of long-chain dicarboxylic C16- and C18-carnitine, i.e. hexadecanedioyl- and octadecanedioyl-carnitine, with high dicarboxylycarnitine/monocarboxylylcarnitine ratio. Elevation of very long-chain acylcarnitines C24- and C26-, i.e. lignoceroyl- and cerotoyl-carnitine, was detected in some PBDs and in D-bifunctional protein deficiency. Similar abnormalities were also found in neonatal screening blood spots. Detection of these compounds alone, in the absence of other shorter-chain acylcarnitines, is highly specific and characteristic of PBD, as confirmed by the differing profiles observed in patients with adrenoleukodystrophy and mitochondrial long-chain fatty acid oxidation defects. Our study adds a novel method to the diagnosis of PBD, which may also be of benefit for future neonatal mass screening programs based on acylcarnitine profiling.     

Pseudo-Zellweger syndrome: deficiencies in several peroxisomal oxidative activities

We describe an infant girl with a clinical, chemical, and pathologic syndrome remarkably similar to Zellweger cerebrohepatorenal syndrome but whose liver parenchymal cells contained abundant peroxisomes. Peroxisomal L-alpha hydroxy acid oxidase, catalase, and the plasmalogen synthesizing enzyme dihydroxy acetone phosphate-acyl transferase activities were normal; other peroxisomal enzymatic activities, including fatty acyl-CoA oxidase and D-amino acid oxidase, were reduced by 80% to 85%. Oxidation of bile acids and pipecolic acid was also deficient. Autopsy revealed the presence of neuronal heterotopia, renal cortical cysts, adrenal atrophy, and accumulation of very long chain fatty acids. The clinical and pathologic features of this case of "pseudo-Zellweger syndrome" reflect a deficiency in multiple peroxisomal activities rather than a defect in peroxisomal biogenesis. The deficient enzymatic activities require flavin adenine dinucleotide, and the underlying defect may be in the utilization of this cofactor.     

Biochemical and morphologic aspects of peroxisomes in the human rectal mucosa: diagnosis of Zellweger syndrome simplified by rectal biopsy

Rectal mucosa biopsy specimens from five controls and three infants with Zellweger syndrome were investigated morphologically and biochemically to elucidate peroxisomal structure and functions in the human rectal mucosa and to develop a simple method for an early postnatal diagnosis of peroxisomal deficiency disorders. After the alkaline 3,3'-diaminobenzidine reaction, peroxisomes of the rectal mucosa from the controls could be identified, electron microscopically, but not light microscopically. However, they were strongly stained using an immunoenzyme technique applied to semi-thin Epon sections and then were clearly visible under the light microscope. However, no positive granules were observed in the specimens of infants with Zellweger syndrome, using either of the two staining techniques. On immunoblot analysis, immunoreactive proteins of peroxisomal acyl-CoA oxidase and 3-ketoacyl-CoA thiolase were present in rectal mucosae from the controls; however, these enzyme proteins were not detected in tissues from the patients. Activity of dihydroxyacetone phosphate acyltransferase was detectable in rectal mucosae from the controls, whereas in those from infants with Zellweger syndrome, the activity of this enzyme was greatly reduced. These observations indicate that the peroxisomal structure and multiple functions are present in the rectal mucosa and that rectal biopsy is of potential value for the early and less invasive detection of Zellweger syndrome and other peroxisomal disorders.     

Peroxisomal β-oxidation defect with detectable peroxisomes: A case with neonatal onset and progressive course

A progressive demyelinating cerebral disorder is described in a normally-appearing female infant with neonatal seizures, progressive psychomotor deterioration, deafness, retinopathy, peripheral neuropathy and loss of myelin observed on magnetic resonance imaging (MRI) scanning. MRI also showed the absence of macroscopic neocortical dysplasia which is usually found in Zellweger syndrome (ZS). Adrenal cortical function was normal. The patient died at the age of 37 months. Extensive biochemical investigations of peroxisomal functions in the patient revealed an impairment of peroxisomal -oxidation resulting in elevated levels of very long (>C₂₂) chain fatty acids in plasma and fibroblasts. Moreover, elevated plasma levels of intermediates of bile acid biosynthesis such as tri- and dihydroxycholestanoic acid were found. Other peroxisomal functions were normal. Immunoblotting of the peroxisomal -oxidation enzyme proteins in liver from the patient revealed normal responses with antisera against acyl-CoA oxidase, bifunctional protein and thiolase respectively. From these data we conclude that the patient had a deficiency of a single peroxisomal -oxidation enzyme at the level of either the bifunctional protein or peroxisomal thiolase with retained immunoreactivity against these enzymes.     

Organelle disease: peroxisomal disorders

Peroxisomes are virtually ubiquitous organelles involved in numerous catabolic and anabolic pathways. Interest in peroxisomes stems from an expanding group of genetic diseases in which there is either deficiency of a specific peroxisomal function (single protein defects) or failure to assemble the organelle resulting in defects of multiple peroxisome functions (peroxisome biogenesis disorders). The paradigm for the former is X-linked adrenoleukodystrophy caused by mutations in the adrenoleukodystrophy gene and, for the latter, Zellweger syndrome caused by mutations in peroxin genes. Conclusion The identification and functional characterisation of the peroxisomal disease genes is proceeding at rapid pace helped immeasurably by work in various yeast model systems. The ultimate goal is to elucidate how the encoded proteins produce normal appearing and functioning peroxisomes. The achievement of this goal will lead to a better understanding of peroxisomal disorders, their pathogenesis and treatment.     

Zellweger syndrome amniocytes: morphological appearance and a simple sedimentation method for prenatal diagnosis

Zellweger syndrome is the prototype of a growing group of genetic diseases caused by an absence or deficiency of peroxisomes. The defect causes the enzyme catalase to remain in the cytosol instead of being packaged into peroxisomes. This mislocalization can be easily detected by sedimentation analysis. Amniocytes were homogenized and then centrifuged to pellet organelles. Catalase was found to sediment with the peroxisomes in the homogenates of normal cells, but to remain in the supernatant with Zellweger syndrome amniocyte homogenates. This striking difference is unambiguous and reproducible, and provides a simple method for prenatal diagnosis. Moreover, it allows one to differentiate diseases in which peroxisomes are deficient from other peroxisomal diseases in which the organelle is intact, but one enzyme is defective. Electron microscopic observations support the biochemical determinations. Normal amniocytes contain small peroxisomes in which a weak cytochemical reaction for catalase may be demonstrated. Zellweger amniocytes appear to lack these organelles, although some cells have rare structures that might be residual or abnormal peroxisomes.     

Peroxisomal acyl CoA oxidase deficiency

Three Japanese patients with peroxisomal acyl coenzyme A oxidase deficiency who manifested psychomotor retardation and regression during the late infantile period showed characteristic patterns of demyelination in the ponto- medullary corticospinal tracts and in the cerebellar and cerebral white matter. Molecular investigations revealed 2 novel missense mutations, M278V and G178C.     

Isolated dihydroxyacetonephosphate-acyl-transferase deficiency in rhizomelic chondrodysplasia punctata: clinical presentation,metabolic and histological findings

Abstract Rhizomelic chondrodysplasia punctata (RCDP) is clinically characterized by symmetrical shortening of the proximal limbs, contractures of joints, a characteristic dysmorphic face, and cataracts. In the classical form an impairment of several peroxisomal functions and enzymes (plasmalogen synthesis, phytanic acid oxidation, 3-oxoacyl-CoA thiolase) has been repeatedly shown. Recently a variant involving only the peroxisomal dihydroxyacetonephosphate acyltransferase (DHAP-AT) has been described. We present a patient with isolated DHAP-AT deficiency and all clinical, radiological, and pathological features of classical RCDP. For the first time, microscopy and immunocytochemistry of hepatocytes could be performed. Conclusion In contrast to studies on classical rhizomelic chondrodysplasia punctata which have shown enlarged peroxisomes in numbers varying from hepatocyte to hepatocyte, the peroxisomes in our patient seem to be normal in size, number and shape.     

Synthesis of mevalonate pathway lipids in fibroblasts from Zellweger and X-linked ALD patients.

Fibroblasts were cultured to determine the involvement of peroxisomes in cholesterol and dolichol synthesis. For this purpose, the behavior of cells from patients with Zellweger syndrome, with X-linked adrenoleukodystrophy, and from nondiseased control subjects was studied. Cells both after pretreatment with mevinolin and without pretreatment were incubated in a medium containing [3H]-mevalonate. In fibroblasts from patients with peroxisomal defects, the cholesterol content and mevalonate incorporation into cholesterol were decreased by 10-20% in comparison with control cells. Mevinolin pretreatment decreased the incorporation rate of [3H]-mevalonate into cholesterol but increased the labeling of ubiquinone and dolichol both in diseased and control cells. Squalene synthase activity was unchanged, whereas the activity of farnesyl-pyrophosphate synthase was increased in the diseased states. The results show that in patients with peroxisomal deficiency neither the amount nor the rate of synthesis of cholesterol and dolichol is reduced to any greater extent.     

Peroxisomal disorders. A review of a recently recognized group of clinical entities

The peroxisome is a small organelle present in almost all cells. The peroxisomal disorders are a newly recognized group of disease entities that share structural and/or functional abnormalities of the peroxisomes, are inherited, and may have profound neurologic and systemic effects. Some of the disorders lack peroxisomes in cells, while others have single or multiple peroxisomal enzymatic deficiencies despite the presence of normally appearing peroxisomes. The prototype of the peroxisomal disorders is Zellweger syndrome. X-linked adrenoleukodystrophy, neonatal adrenoleukodystrophy, infantile Refsum disease, hyperpipecolic acidemia and Refsum disease are some of the other disease entities presently classified as peroxisomal disorders. Accurate methods of pre- and postnatal diagnosis are available. Treatment strategies are being developed, but at this time prenatal diagnosis and appropriate genetic counseling is the best therapeutic intervention for those peroxisomal disorders characterized by profound neurologic handicap and early death.     

D-bifunctional protein deficiency with fetal ascites, polyhydramnios, and contractures of hands and toes.

Fetal abnormalities including chylous ascites, polyhydramnios, claw hands, and hammer toes were identified in an infant who had a missense mutation R106P and a 52bp deletion in the gene for a peroxisomal beta-oxidation enzyme, D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase, D-bifunctional protein. The patient had psychomotor retardation and craniofacial dysmorphism and died at 7 months of age. The patient had atypical fetal manifestations of this enzyme deficiency.     

Biochemical abnormalities in rhizomelic chondrodysplasia punctata

Biochemical studies with emphasis on peroxisomal functions were conducted in six patients with well-documented rhizomelic chondrodysplasia punctata (RCDP) and compared with findings in patients with Zellweger syndrome and neonatal adrenoleukodystrophy (ALD). Patients with RCDP had three characteristic biochemical abnormalities: (1) profound defect in plasmalogen (ether lipid) synthesis, which is significantly greater than the analogous defect in Zellweger syndrome or neonatal ALD; (2) reduction of phytanic acid oxidation activity to 1% to 5% of control, similar to that observed in Refsum disease, Zellweger syndrome, and neonatal ALD; (3) presence of the unprocessed form of peroxisomal 3-oxoacyl-coenzyme A thiolase in the postmortem liver of two patients. Other peroxisomal functions were normal, including levels of very long chain fatty acids, pipecolic acid, and bile acid intermediates, and immunoblot studies of peroxisomal acyl-CoA oxidase and bifunctional enzyme in postmortem liver. Unlike what is observed in Zellweger syndrome and neonatal ALD, catalase activity in cultured skin fibroblasts was sedimentable, indicating that peroxisome structure is not grossly deficient in RCDP. The biochemical abnormalities in RCDP were consistent and set it apart from all the other known peroxisomal disorders.     

Rhizomelic Chondrodysplasia Punctata: Report of a Case with Review of the Literature and Correlation with Other Peroxisomal Disorders

A 3-year-old girl rhizomelic chondrodysplasia punctata (RCDP) had serve micrencephaly but a normal gyral pattern, neuronal density, and cortical cytoarchitecture. The white matter was diffusely decreased in mass but normally myelinated. There was optic atrophy and cerebellar degeneration. Leukodystrophy in peroxisomal disorders is caused by elevated very long chain fatty acids. The absence of a fatty acid abnormality in RCDP explains the normal myleination. Cerebellar and retinal degeneration and possible stunted dendritogenesis may be due to plasmalogen deficiency, which is the most severe biochemical abnormality in RCDP.     

The 22-kD peroxisomal integral membrane protein in Zellweger syndrome--presence, abundance, and association with a peroxisomal thiolase precursor protein.

The primary genetic defect of Zellweger syndrome may be related to defective synthesis or impaired import of peroxisomal proteins. We analyzed the presence and measured the abundance of the 22-kD peroxisomal integral membrane protein (PMP) in patients with Zellweger syndrome. We determined the intracellular localization of the 22-kD PMP and compared it with the localization of a peroxisomal 44-kD thiolase precursor protein. The 22-kD PMP was quantified by immunoblot analyses in liver tissue (n = 7 patients). Immunoblot signals were evaluated using transmission photometry. The intracellular localization of the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were determined by immunoblot analyses on fibroblast subcellular fractions prepared by Nycodenz (n = 5 patients) or sucrose density gradient centrifugation (n = 2 patients). The 22-kD PMP was present and associated with membrane fractions in all patients. Its abundance varied in patients as compared with normal human liver controls. The 22-kD PMP was located in subcellular membrane fractions having a lower density than normal peroxisomes or mitochondria. Using two different gradient techniques, the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were found in the same low-density gradient fractions. These results suggest that in Zellweger syndrome peroxisome-like elements containing both the 22-kD PMP and a 44-kD thiolase precursor protein are formed. Globally defective synthesis or import of peroxisomal proteins is therefore unlikely to be the primary genetic defect in the patients we studied.     

Peroxisomal proliferation in heart and liver of mice receiving chlorpromazine, ethyl 2(5(4-chlorophenyl)pentyl) oxiran-2-carboxylic acid or high fat diet: a biochemical and morphometrical comparative study

Chlorpromazine and related drugs including trifluoperazine, clopenthixol, and fluphenazine are in vitro inhibitors of mitochondrial carnitine palmitoyltransferase and cytochrome c oxidase and of peroxisomal carnitine octanoyltransferase from mouse heart and liver. By contrast with 0.1% ethyl 2(5(4-chlorophenyl)pentyl) oxiran-2-carboxylic acid or 0.1% clofibrate-containing diets, the treatment of mice with 0.1% chlorpromazine-containing diet fails to induce peroxisomal proliferation in liver and heart. An 0.5% chlorpromazine-containing diet did induce peroxisomal proliferation. Inhibition of peroxisomal beta-oxidation presumably via the reduction of carnitine octanoyltransferase by chlorpromazine elicits the appearance in liver of lamellar structures resembling those seen in human peroxisomal disorders and induces accumulation of very long-chain fatty acids in plasma. The peroxisomal proliferation induced by administration of high dose chlorpromazine is ascribed to its ability to depress mitochondrial fatty acid oxidation by impairing cytochrome c oxidase and carnitine palmitoyltransferase activities.     

Deficiency of plasmalogens in the cerebro-hepato-renal (Zellweger) syndrome

We have analyzed the phospholipid composition of various organs of patients with the cerebro-hepato-renal (Zellweger) syndrome. The phospholipid composition of tissues from controls and patients was very similar except for their plasmalogen contents. In controls about 50% of the phosphatidylethanolamine fraction of brain, heart, kidney and skeletal muscle and about 10% of that fraction in control liver tissue was found to consist of plasmalogen. In control heart muscle, but not in other control tissues about 25% of the phosphatidylcholine fraction consist of plasmalogens. In contrast, plasmalogens were nearly absent in the corresponding tissues of Zellweger patients.The amount of phosphatidylethanolamine plasmalogens in both erythrocytes and fibroblasts of Zellweger patients is lowered significantly compared to control erythrocytes and control fibroblasts respectively, although this reduction is not as dramatic as in brain, heart, kidney, skeletal muscle and liver of patients. Phosphatidylcholine-plasmalogens are only present in low amounts in both controls, heterozygotes and patients.In recent years considerable evidence has accumulated to show that peroxisomes are involved in cellular lipid metabolism. Notably, the key enzymes of ether lipid (plasmalogen) biosynthesis in rodents were recently found to be located in peroxisomes. Since electronmicroscopic studies have shown that peroxisomes are absent in liver and kidney of patients with the cerebro-hepato-renal syndrome, our results suggest that an inability to integrate these key enzymes in a functional peroxisome leads to a severe disturbance in plasmalogen biosynthesis.We propose that the multiple clinical and biochemical defects in Zellweger patients are secondary to a deficiency in peroxisomal function.     

Metabolic disorders presenting as liver disease

A wide range of inherited metabolic disorders lead to biochemical disturbances within the liver. A number of disorders of energy metabolism present as hepatomegaly with hypoglycaemia e.g. glycogen storage diseases or with hypoketotic hypoglycaemia e.g. disorders of fat oxidation. Other defects of carbohydrate metabolism also present with hypoglycaemia and liver disease either in neonates e.g. galactosaemia and fructose-1,6-bisphosphatase deficiency or at weaning i.e. hereditary fructose intolerance. Mitochondrial respiratory chain defects frequently present in neonates/infants as liver disease but often there is other (multi)-organ involvement and persistent lactic acidaemia. Many disorders of peroxisomal and lysosomal metabolism cause a spectrum of liver dysfunction. Urea cycle disorders manifest as hyperammonaemia often presenting acutely in neonates but also in older children and adults. Other causes of liver disease include disorders of copper, bile acid and bilirubin metabolism. Definitive diagnosis requires specialist expertise, however once clinical liver disease is apparent, most disorders are associated with characteristic findings on routine laboratory testing that should raise the suspicion of metabolic disease.     

Congenital rubella syndrome associated with calcific epiphyseal stippling and peroxisomal dysfunction

An infant girl had the clinical and immunologic findings of congenital rubella syndrome but also had arthrogryposis multiplex and calcific epiphyseal stippling. Spastic quadriparesis developed, and both physical and behavioral development were slow. Increased spasticity of the legs at 5 1/2 years was related not to progressive rubella encephalomyelopathy but to spinal cord compression by abnormal cartilaginous tissue. The presence of a peroxisomal disorder was demonstrated by a greatly increased level of phytanic acid and slightly increased levels of hexacosanoate in serum and by reduced activity of peroxisomal dihydroxyacetone phosphate acyltransferase and a slightly increased ratio of cytosolic to peroxisomal catalase activity in cultured fibroblasts. A reduction in the number and size of peroxisomes was demonstrated in cultured fibroblasts, and a needle biopsy specimen of the liver also showed the peroxisomes to have a smaller diameter than usual. We recommend that any child with epiphyseal stippling be assessed for peroxisomal disease and that the potential for spinal cord compression by dysplastic bone or cartilage be recognized. The association of peroxisomal dysfunction with congenital rubella has not been described previously. The interaction between rubella virus infection and peroxisomal function may need further investigation.