[Disorders of neuronal migration in Zellwegers cerebrohepato-renal syndrome (author's transl)]

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.

A Golgi study of the cerebral cortex in Fukuyama-type congenital muscular dystrophy, Walker-type "lissencephaly," and classical lissencephaly

The cortical neuronal organization of the brain was studied and compared in three conditions. The neurons in the polymicrogyric cortex from a subject with Fukuyama-type congenital muscular dystrophy and from a child with ocular dysplasia (Walker-type lissencephaly) were large, irregularly aligned, and not completely mature. In the former condition, the abnormal neuronal arrangement was predominantly in the superficial cortex; in the latter both the superficial and deep cortex were involved. These two diseases may have a similar pathogenetic mechanism. In classical lissencephaly without evidence of other disease manifestations, the neurons were arranged in a radial pattern with heterotopia but no large neurons. The pathogenesis of these conditions is discussed.

Zellweger syndrome: diagnostic assays, syndrome delineation, and potential therapy

Patients with the cerebrohepatorenal syndrome of Zellweger lack peroxisomes and certain peroxisomal enzymes such as dihydroxyacetone phosphate acyltransferase in their tissues. Deficiency of this enzyme, which is necessary for glycerol ether lipid synthesis, provides a biochemical method for recognizing patients with subtle manifestations of Zellweger syndrome and suggests the utility of exogenous ether lipid precursors as a therapeutic strategy for these children. We describe the results of glycerol ether lipid supplementation to two children, one with classic Zellweger syndrome and 9% of control fibroblast dihydroxyacetone phosphate acyltransferase activity, and one with mild facial manifestations, wide sutures, hypotonia, developmental delay, hepatomegaly, peripheral retinal pigmentation, and 50% of control fibroblast dihydroxyacetone phosphate acyltransferase activity. An increase in erythrocyte plasmalogen levels following therapy was clearly demonstrated in the milder patient, and neither patient showed evidence of toxicity. Evaluation of therapy by comparison to the usual clinical course of Zellweger syndrome was not helpful because of the variability and incomplete documentation of 90 previously reported cases. The literature survey did provide criteria for classic Zellweger syndrome, which include hypotonia with or without deformation of limbs, large fontanels and split sutures, prominent forehead, flattened facial profile with hypoplastic supraorbital ridges, anteverted nares, highly arched palate, cryptorchidism or labial hypoplasia, hepatomegaly or elevated liver enzymes, peripheral pigmentation of the retina, renal cortical cysts, and characteristic neuropathology involving decreased myelinization, abnormal neuronal migration, and sudanophilic macrophages. Less severe patients, as exemplified by our case 2 and others from the literature, will not have all the classic features and can be recognized only by a growing panel of biochemical indicators. Our patient studies illustrate the complexity of designing comprehensive therapy for Zellweger-like conditions, suggest other diseases that may involve peroxisomal alterations, and emphasize the need for multicenter, collaborative studies to evaluate biochemical heterogeneity and therapy of peroxisomal disorders.

Neonatal adrenoleukodystrophy: new cases, biochemical studies, and differentiation from Zellweger and related peroxisomal polydystrophy syndromes

Eight new cases of autopsy-confirmed or suspected neonatal adrenoleukodystrophy (NALD) are presented together with new biochemical data on very-long-chain fatty acids (VLCFA) and plasmalogens and a review of all previously published cases. The clinical, biochemical, and histopathologic abnormalities characteristic of this newly recognized form of adrenoleukodystrophy are analyzed in detail and compared to the principal characteristics of the similar disorder, the cerebrohepatorenal syndrome of Zellweger (ZS). Using strict pathologic criteria for the diagnosis of NALD, we find that, despite many clinical resemblances, NALD and the ZS are distinguishable on the basis of histology and peroxisomal biochemistry. Patients with NALD demonstrate adrenal atrophy, systemic infiltration by abnormal lipid-laden macrophages, and elevations of saturated VLCFA. In contrast, patients with ZS have chondrodysplasia, glomerulocystic disease of the kidney, central nervous system dysmyelination, and elevations of unsaturated as well as saturated VLCFA, but they lack adrenal atrophy. We conclude that NALD and the ZS probably represent at least two different genetic defects.

The cerebro-hepato-renal (Zellweger) syndrome: lamellar lipid profiles in adrenocortical, hepatic mesenchymal, astrocyte cells and increased levels of very long chain fatty acids and phytanic acid in the plasma

Clinical, radiological, histological and biochemical aspects of two cases of cerebro-hepato-renal syndrome (CHRS) are reported. CT scan disclosed a demyelinating process and gyral abnormalities reflecting the observed neuropathological findings. Trilamellar and lamellar inclusions were found in brain astrocytes, hepatic mesenchymal and adrenal cells. The morphologic features of these inclusions are similar to those observed in childhood adrenoleukodystrophy, neonatal adrenoleukodystrophy and infantile Refsum's disease. In the two CHRS patients, increased plasma levels of very long chain fatty acids (C26:1, C26:0) and phytanic acid were in the same range as those observed in seven other instances of neonatal adrenoleukodystrophy. The presence of increased plasma levels of phytanic acid in these disorders suggests that phytanate oxidase activity is, at least, partially located in peroxisomes.

Mitochondrial myopathy with loosely coupled oxidative phosphorylation in a case of Zellweger syndrome. A cytochemical-ultrastructural study

A newborn female, the second child of consanguineous parents, exhibited general muscle hypotonia, apathy, hepatomegaly and failure to thrive from birth and signs of craniofacial dysmorphia were present. Pipecolic and trihydroxicoprostanoic acid were excreted in the urine and serum transferrin, ferritin and iron were markedly elevated. At the age of 7 weeks the baby died of respiratory insufficiency. Besides malformations of the brain, renal cysts, liver damage with hypoplastic intrahepatic bile ducts and cholestasis, increased storage of iron and cytochemically proven deficiency of peroxisomes in liver and kidney, morphological studied provided evidence of a mitochondrial myopathy in striated muscle with the accumulation of enlarged bizarre mitochondria, showing only minor structural abnormalities. No defects of NADH-reductase, succinate-dehydrogenase or cytochrome-c-oxidase were demonstrated histochemically. Cytochemical-ultrastructural investigation of mitochondrial ATPase revealed activation of the ATP-synthesising enzyme even before the addition of an uncoupler, this indicating loosely coupled oxidative phosphorylation. In addition a high rate of subcellular autophagy with segregation of mitochondria and focal loss of fibrils was present. Muscle damage in Zellweger syndrome appears to be the consequence of complex, interacting metabolic processes. The mitochondrial myopathy thereby induced allows a better understanding of general muscle hypotonia, one of the leading symptoms of this disorder.

[Morphology and diagnosis of Zellweger syndrome. A contribution to combined cytochemical-finestructural identification of peroxisomes in autopsy material and frozen liver tissue with case report]

A female newborn, the second child of healthy non consanguineous parents, exhibited muscular hypotonia, areflexia, apathy, seizures, hepatomegaly and failure to thrive since birth. The peculiar skull shape was lacking. In the urine pipecolic acid and trihydroxycoprostanoic acid were excreted. At the age of seven weeks she died of bronchopneumonia. Lightmicroscopy revealed malformations and deficiency of myelinisation in the brain, renal cysts and fatty metamorphosis in the enlarged liver, which showed only minimal siderosis. Ultrastructurally no peroxisomes could be found in liver and kidney. No peroxisomes were detected by histochemical demonstration of catalase in frozen liver tissue which was taken immediately after death and stored for three months. Absence of peroxisomes is pathognomonic for the cerebro-hepato-renal syndrome of Zellweger and occurs in the liver irrespective of duration and degree of liver damage. It is best demonstrated by enzymehistochemical electron microscopy. With this method peroxisomes can be visualized even 30 h post mortem. In deep frozen normal liver tissue the activity of catalase remains very stable and enables the identification of peroxisomes even after a 12 months period of storage. In the cerebro-hepato-renal syndrome of Zellweger, frozen liver tissue should be stored for biochemical and diagnostic enzymehistochemical studies.

Glycogen accumulation in the central nervous system in the cerebro-hepato-renal syndrome. Report of a case with ultrastructural studies

We found marked accumulation of glycogen in the brain in one case of the cerebro-hepato-renal syndrome (CHRS). Glycogen in the form of beta-particles was deposited freely within the nucleus, perikaryon and cell processes of neurons and glial cells. The changes involved the gray matter diffusely but were more prominent in the cerebral cortex. The patient died at the age of 4 months after a clinical course characterized by severe hypotonia, seizures, and apneic episodes. Other neuropathologic findings were developmental malformations of the central nervous systen (CNS) (pachygyria, polymicrogyria, and hypoplasia of the inferior olives), white matter abnormalities (deficiency in myelination and diffuse accumulation of sudanophilic droplets within glial cells), clusters of peculiar "globoid" histiocytes with pleomorphic lipid inclusions, and microglial nodules in gray and white matter. This unusual combination of findings is regarded as characteristic of the CHRS.

Globoid cells, glial nodules, and peculiar fibrillary changes in the cerebro-hepato-renal syndrome of Zellweger

In addition to a distinct malformation (pachymicrogyria, heterotaxic lamination of the cerebellar cortex, olivary dysplasia), unusual degenerative changes were found in the nervous system of 2 unrelated babies with the Zellweger syndrome. Cerebral clefts were present in 1 case. In both infants there was neuron loss and accumulation of glial nodules and globoid cells in the gray matter as well as degeneration of the white matter. There was fatty change in astrocytes and diffuse gliosis. Neurons in the column of Clarke and the lateral cuneate nucleus showed peculiar fibrillary changes. Cytoplasmic inclusion bodies were seen in the spinal ganglia. Swelling of cortical astrocytes was remarkable in the older infant. The combination of a rare malformation with the cell changes described here gives the syndrome a unique neuropathological profile.

Cerebral malformation associated with metabolic disorder. A report of 2 cases

A clinical and neuropathological study is presented of two cases each of which showed neuronal heterotopia. Microgyria was also present in one case. One patient was suffering from a degenerative disorder affecting the white matter. The other was a case of Menkes' disease. It is suggested that the antenatal damage may have been caused by an imbalance of the maternal metabolism, the predisposing factor being the mother's carrier state for a metabolic defect. This is the first report of teratogenesis in a case of Menkes' disease. It is also noted that in this case there is interference with the postnatal as well as the antenatal development of the brain.

Neuropathological considerations in cerebro-hepato-renal syndrome (Zellweger's syndrome)

The nervous system in patients with cerebro-hepato-renal syndrome appeared to be affected at various tissue levels. There was evidence of a migrational disorder manifested by polymicrogyria and lack of normal neuronal maturation. There was dysmyelination of the white matter associated with accumulation of neutral fat in astrocytes. Within the peripheral nerves, masses of tangled neurofilaments producing dystrophic axons were demonstrated by electron microscopy. These findings could be explained on the basis of a genetic metabolic defect, one that involved particularly the amino acids. The defect may have interfered with the normal intercellular reaction during embryogenesis resulting in the malformation of multiple organs. The same metabolic abnormality could have caused the hepatic damage and disturbance in normal myelination during the neonatal period.

Studies of malformation syndromes of man XIB: the cerebro-hepato-renal syndrome of Zellweger: comparative pathology

A study of 11 autopsied cases of the cerebro-hepato-renal syndrome of Zellweger (ZS) is reported. All cases had severe, persistent congenital hypotonia, hepatic lobular disarray, renal cortical cysts and pulmonary hypoplasia. Many had cardiovascular malformations, hepatomegaly, cerebral cortical gyral maldevelopment and pancreatic islet hyperplasia. Additional, less frequent findings are delineated. Results of iron content studies of hepatic and renal tissues are related to age of survival and possible development of fibrosis.