A case of pseudo-Zellweger syndrome with a possible bifunctional enzyme deficiency but detectable enzyme protein. Comparison of two cases of Zellweger syndrome

Brain imaging in children with neonatal cholestatic liver disease: A systematic review

AIM

To determine if children with neonatal cholestatic liver disease had concurrent and later findings on brain imaging studies that could be attributed and the cholestasis to contribute to the understanding of the impaired neuropsychological development.

METHODS

Ovid MEDLINE and EMBASE were searched on July 21, 2022, and updated on March 26, 2023. Studies with children under 18 years of age with neonatal cholestasis and a brain scan at the time of diagnosis or later in life were included. Excluded studies were non-English, non-human, reviews or conference abstracts. Data were extracted on demographics, brain imaging findings, treatment and outcome. The results were summarised by disease categories. Risk of bias was assessed using JBI critical appraisal tools.

RESULTS

The search yielded 12 011 reports, of which 1261 underwent full text review and 89 were eligible for inclusion. Haemorrhage was the most common finding, especially in children with bile duct obstruction, including biliary atresia. Some findings were resolved after liver transplantation.

CONCLUSION

Children with neonatal cholestasis had changes in brain imaging, which might play a role in impaired neuropsychological development, but longitudinal clinical research with structured assessment is needed to better qualify the aetiology of the impairment.

Peroxisomal multifunctional protein-2: the enzyme, the patients and the knockout mouse model

The mammalian multifunctional protein-2 (MFP-2, also called multifunctional enzyme 2, D-bifunctional enzyme or 17-beta-estradiol dehydrogenase type IV) was identified by several groups about a decade ago. It plays a central role in peroxisomal beta-oxidation as it handles most, if not all, peroxisomal beta-oxidation substrates. Deficiency of this enzyme in man causes a severe developmental syndrome with abnormalities in several organs but in particular in the brain, leading to death within the first year of life. Accumulation of branched-long-chain fatty acids and very-long-chain fatty acids and a disturbed synthesis of bile acids were documented in these patients. A mouse model with MFP-2 deficiency only partly phenocopies the human disease. Although the expected metabolic abnormalities are present, no neurodevelopmental aberrations are observed. However, the survival of these mice into adulthood allowed to document the importance of this enzyme for the normal functioning of the brain, eyes and testis. In the present review, the identification and biochemical characteristics of MFP-2, and the consequences of MFP-2 dysfunction in humans and in mice will be discussed.

Developmental and pathological expression of peroxisomal enzymes: their relationship of D-bifunctional protein deficiency and Zellweger syndrome

We present the developmental changes of peroxisomal enzymes, catalase, L-bifunctional protein (L-BF) and D-bifunctional protein (D-BF), in the normal brains, and patients with D-BF deficiency, a new peroxisomal disease. D-BF immunoreactivity was observed in controls as early as 13 gestational weeks (GW) and increased with maturation. The adult pattern with fine granule staining of somata and dendrites became apparent in adolescence. L-BF appeared at 20 GW in the cerebral cortex and Purkinje cells and positive glia appeared early in the white matter at 17 GW, and then increased with age. Catalase-positive neurons were identified in the same manner as L-BF, D-BF deficiency in both fetus and infant showed markedly diminished enzyme immunoreactivity. Patients demonstrate reduced D-BF expression. Zellweger syndrome shows decreased expression for the three proteins. This study shows that the peroxisomal enzymes may be closely related to neuronal maturation and gliogenesis in human brain and to disturbance of neuronal migration as seen in Zellweger syndrome significant. D-BF deficiency may exhibit a range of symptoms during the neonatal and early infantile periods some of which may be similar to Zellweger syndrome.

D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein deficiency: a newly identified peroxisomal disorder

Peroxisomal beta-oxidation proceeds from enoyl-CoA through D-3-hydroxyacyl-CoA to 3-ketoacyl-CoA by the D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxy-acyl-CoA dehydrogenase bifunctional protein (d-bifunctional protein), and the oxidation of bile-acid precursors also has been suggested as being catalyzed by the d-bifunctional protein. Because of the important roles of this protein, we reinvestigated two Japanese patients previously diagnosed as having enoyl-CoA hydratase/L-3-hydroxyacyl-CoA dehydrogenase bifunctional protein (L-bifunctional protein) deficiency, in complementation studies. We found that both the protein and the enzyme activity of the d-bifunctional protein were hardly detectable in these patients but that the active L-bifunctional protein was present. The mRNA level in patient 1 was very low, and, for patient 2, mRNA was of a smaller size. Sequencing analysis of the cDNA revealed a 52-bp deletion in patient 1 and a 237-bp deletion in patient 2. This seems to be the first report of D-bifunctional protein deficiency. Patients previously diagnosed as cases of L-bifunctional protein deficiency probably should be reexamined for a possible d-bifunctional protein deficiency.

Peroxisomal bifunctional enzyme deficiency: serial neurophysiological examinations of a case

We report on a case of 21-month-old girl with peroxisomal bifunctional enzyme deficiency, which was diagnosed by means of complementation analysis. Serial neurophysiological examinations were also carried out. The motor and sensory nerve conduction velocities of the median nerve showed lower borderline values at 3 months of age and were within range at 11 months of age. Later, those velocities gradually decreased. The electrically elicited blink reflex at 3 months of age showed the prolongation of latencies of R1, R2 and R2' and the interpeak latencies of R1-R2 and R1-R2'. Furthermore, R1, R2 and R2' showed prolonged latencies at 11 months of age and were absent at 15 months of age. The auditory brainstem response (ABR) showed, bilaterally, normal latency of wave I, prolonged interpeak latencies of waves I-V. At 11 months of age, waves III and IV-V of ABR were detected, but their amplitude was very low. At the age of 15 months ABR was absent. These results and the following report are valuable for understanding the pathogenesis of neurological symptoms.

The human peroxisomal multifunctional protein involved in bile acid synthesis: activity measurement, deficiency in Zellweger syndrome and chromosome mapping

The dehydrogenation of 24R,25R-varanoyl-CoA, the physiological intermediate formed during the peroxisomal breakdown of the bile acid intermediate trihydroxycoprostanic acid, was studied in human liver. The reaction appeared to be catalyzed by two different enzymes. A first one, present in the cytosol, did not discriminate between the four possible varanoyl-CoA isomers and did not require the CoA moiety. The second enzymic activity was associated with peroxisomes and acted only on the 24R,25R-isomer, in which the 24-hydroxy group possesses the D-configuration. The D-specific dehydrogenase is part of a 79 kDa protein which represents the human counterpart of a recently discovered second multifunctional protein in rat liver peroxisomes, named multifunctional protein 2 (MFP-2). Human MFP-2, like its rat counterpart, is also responsible for the formation (by hydratation) of 24R,25R-varanoyl-CoA. A deficiency of MFP-2 in Zellweger liver could be demonstrated immunologically by using antibodies against the rat enzyme and enzymically -- after removal of the cytosol -- by using 24R,25R-varanoyl-CoA. The gene coding for MFP-2 was mapped to chromosome 5q2.3.

Epilepsy in peroxisomal diseases

PURPOSE

To clarify the electroclinical manifestation of epileptic seizures and the evolution of epilepsy in patients with peroxisomal diseases.

METHODS

Retrospective review of the medical records and EEGs of 14 patients with peroxisomal diseases: seven with Zellweger syndrome (ZS), two with neonatal adrenoleukodystrophy (NALD), two with acyl-CoA oxidase deficiency (AOXD), two with bifunctional enzyme deficiency (BFED), and one with rhizomelic chondrodysplasia punctata (RCDP). The diagnoses were made by biochemical analysis and pathological examinations in our laboratory.

RESULTS

Patients manifested serious neurologic deficits in the neonatal period or in early or late infancy. Patients with ZS or AOXD had partial motor seizures originating in the arms or legs or corners of the mouth. Their seizures did not culminate in generalized tonic-clonic seizures and were easily controlled by antiepileptic drugs (AEDs). Interictal EEGs of the patients with ZS showed infrequent bilateral independent multifocal spikes, predominantly in the frontal motor cortex and its surrounding regions. The EEGs of patients with AOXD showed interictal fast theta activity, predominantly in the frontocentral regions. Patients with BFED also had partial motor seizures in early infancy, but the seizures were intractable, evolving in one case to myoclonic seizures. Interictal EEGs of patients with BFED showed bilateral independent multifocal spikes that evolved to bilateral diffuse high-voltage slow waves in one case and to a hypsarythmic pattern in another case as the disease progressed. Patients with NALD had intractable tonic seizures or epileptic spasms. Interictal EEGs showed high-voltage slow waves and bilateral independent multifocal spikes, evolving in one patient to a flat pattern. The patient with RCDP, whose interictal EEGs showed frequent multifocal independent spikes, did not have epileptic seizures.

CONCLUSIONS

The age of epilepsy onset or the duration of survival is related to the types of seizures occurring in patients with peroxisomal diseases. Neonates or young infants usually have partial motor seizures (facial twitching or clonic convulsions of the arms or legs) of various multifocal origins. Older infants may have generalized seizures at the onset of the disease or evolutionally. Seizure intractability is usually less severe in patients with ZS or AOXD than in patients with NALD or BFED. There is no relation between the electroclinical characteristics of epilepsy and the genetic complementation groups in peroxisomal diseases.

Oxidation of pristanic acid in fibroblasts and its application to the diagnosis of peroxisomal beta-oxidation defects

Pristanic acid oxidation measurements proved a reliable tool for assessing complementation in fused heterokaryons from patients with peroxisomal biogenesis defects. We, therefore, used this method to determine the complementation groups of patients with isolated defects in peroxisomal beta-oxidation. The rate of oxidation of pristanic acid was reduced in affected cell lines from all of the families with inherited defects in peroxisomal beta-oxidation, thus excluding the possibility of a defective acyl CoA oxidase. Complementation analyses indicated that all of the patients belonged to the same complementation group, which corresponded to cell lines with bifunctional protein defects. Phytanic acid oxidation was reduced in fibroblasts from some, but not all, of the patients. Plasma samples were still available from six of the patients. The ratio of pristanic acid to phytanic acid was elevated in all of these samples, as were the levels of saturated very long chain fatty acids (VLCFA). However, the levels of bile acid intermediates, polyenoic VLCFA, and docosahexaenoic acid were abnormal in only some of the samples. Pristanic acid oxidation measurements were helpful in a prenatal assessment for one of the families where previous experience had shown that cellular VLCFA levels were not consistently elevated in affected individuals.

MRI findings of Zellweger syndrome

A patient with Zellweger syndrome, who manifested marked dilatation of the lateral ventricles, observed at 34 weeks gestation by fetal ultrasonography, is reported. Postnatal magnetic resonance imaging revealed marked colpocephaly and hypogenesis of the posterior part of the corpus callosum. However, pachygyria was limited to the perisylvian regions. Biochemical diagnosis was based on increased serum very-long-chain fatty acids, 2-hydroxysebacic aciduria, and the detection of the ghosts of peroxisomal membrane in cultured fibroblasts. The patient was classified as belonging to group B of this syndrome by complementation study.