Novel PEX1 mutations and genotype-phenotype correlations in Australasian peroxisome biogenesis disorder patients

The peroxisome biogenesis disorders (PBDs) are a group of neuronal migration/neurodegenerative disorders that arise from defects in PEX genes. A major subgroup of the PBDs includes Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD). These three disorders represent a clinical continuum with Zellweger syndrome the most severe. Mutations in the PEX1 gene, which encodes a protein of the AAA ATPase family involved in peroxisome matrix protein import, account for the genetic defect in more than half of the patients in this PBD subgroup. We report here on the results of PEX1 mutation detection in an Australasian cohort of PEX1-deficient PBD patients. This screen has identified five novel mutations, including nonsense mutations in exons 14 and 19 and single nucleotide deletions in exons 5 and 18. Significantly, the allele carrying the exon 18 frameshift mutation is present at moderately high frequency (approx. 10%) in this patient cohort. The fifth mutation is a missense mutation (R798G) that attenuates, but does not abolish PEX1 function. We have evaluated the cellular impact of these novel mutations, along with that of the two most common PEX1 mutations (c.2097-2098insT and G843D), in PBD patients by determining the levels of PEX1 mRNA, PEX1 protein, and peroxisome protein import. The findings are consistent with a close correlation between cellular phenotype, disease severity, and PEX1 genotype.     

Novel mutations in the PEX12 gene of patients with a peroxisome biogenesis disorder

The peroxisome biogenesis disorders (PBDs) form a genetically and clinically heterogeneous group of disorders due to defects in at least 11 distinct genes. The prototype of this group of disorders is Zellweger syndrome (ZS), with neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) as milder variants. Liver disease, variable neurodevelopmental delay, retinopathy and perceptive deafness are common to PBDs. PBD patients belonging to complementation group 3 (CG3) have mutations in the PEX12 gene, which codes for a protein (PEX12) that contains two transmembrane domains, and a zinc-binding domain considered to be important for its interaction with other proteins of the peroxisomal protein import machinery. We report on the identification of five PBD patients belonging to CG3. Sequence analysis of their PEX12 genes revealed five different mutations, four of which have not been reported before. Four of the patients have mutations that disrupt the translation frame and/or create an early termination codon in the PEX12 open reading frame predicted to result in truncated protein products, lacking at least the COOH-terminal zinc-binding domain. All these patients display the more severe phenotypes (ZS or NALD). The fifth patient expresses two PEX12 alleles capable of encoding a protein that does contain the zinc-binding domain and displayed a milder phenotype (IRD). The three biochemical markers measured in fibroblasts (DHAPAT activity, C26:0 beta-oxidation and pristanic acid beta-oxidation) also correlated with the genotypes. Thus, the genotypes of our CG3 patients show a good correlation with the biochemical and clinical phenotype of the patients.     

Identification of the molecular defect in patients with peroxisomal mosaicism using a novel method involving culturing of cells at 40 degrees C: implications for other inborn errors of metabolism

The peroxisome biogenesis disorders (PBDs), which comprise Zellweger syndrome (ZS), neonatal adrenoleukodystrophy, and infantile Refsum disease (IRD), represent a spectrum of disease severity, with ZS being the most severe, and IRD the least severe disorder. The PBDs are caused by mutations in one of the at least 12 different PEX genes encoding proteins involved in the biogenesis of peroxisomes. We report the biochemical characteristics and molecular basis of a subset of atypical PBD patients. These patients were characterized by abnormal peroxisomal plasma metabolites, but otherwise normal to very mildly abnormal peroxisomal parameters in cultured skin fibroblasts, including a mosaic catalase immunofluorescence pattern in fibroblasts. Since this latter feature made standard complementation analysis impossible, we developed a novel complementation technique in which fibroblasts were cultured at 40 degrees C, which exacerbates the defect in peroxisome biogenesis. Using this method, we were able to assign eight patients to complementation group 3 (CG3), followed by the identification of a single homozygous c.959C>T (p.S320F) mutation in their PEX12 gene. We also investigated various peroxisomal biochemical parameters in fibroblasts at 30 degrees C, 37 degrees C, and 40 degrees C, and found that all parameters showed a temperature-dependent behavior. The principle of culturing cells at elevated temperatures to exacerbate the defect in peroxisome biogenesis, and thereby preventing certain mutations from being missed, may well have a much wider applicability for a range of different inborn errors of metabolism.     

Prader-Willi syndrome: causes of death in an international series of 27 cases

The peroxisome biogenesis disorders (PBDs) with generalized peroxisomal dysfunction include Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD). There is clinical, biochemical, and genetic overlap among the three phenotypes, also known as Zellweger spectrum disorders. Clinical distinctions between the phenotypes are not sharply defined. Only limited sources are available to serve as a background for prognosis in PBD, especially in case of prolonged survival. We delineated the natural history of 31 PBD patients (age 1.2-24 years) through systematic clinical and biochemical investigations. We excluded classical ZS from our study, and included all patients with a biochemically confirmed generalized peroxisomal disorder over 1 year of age, irrespective of the previously diagnosed phenotype. The initial clinical suspicion, age at diagnosis, growth, development, neurological symptoms, organ involvements, and survival are summarized. Common to all patients were cognitive and motor dysfunction, retinopathy, sensorineural hearing impairment, and hepatic involvement. Many patients showed postnatal growth failure, 10 patients displayed hyperoxaluria of whom 4 had renal stones. Motor skills ranged from sitting with support to normal gait. Speech development ranged from non-verbal expression to grammatical speech and comprehensive reading. The neurodevelopmental course was variable with stable course, rapid decline with leukodystrophy, spinocerebellar syndrome, and slow decline over a wide range of faculties as outcome profiles. At the molecular level, 21 patients had mutations in the PEX1 gene. The two most common PEX1 mutations were the G843D (c.2528G-->A) missense and the c.2097insT frameshift mutation. Patients having the G843D/G843D or the G843D/c.2097insT genotypes were compared. Patients homozygous for G843D generally had a better developmental outcome. However, one patient who was homozygous for the "mild" G843D mutation had an early lethal disease, whereas two other patients had a phenotype overlapping with the G843D/c.2097insT group. This indicates that next to the PEX1 genotype other yet unknown factors determine the ultimate phenotype.     

Peroxisomal disorders I: biochemistry and genetics of peroxisome biogenesis disorders

The peroxisomal disorders represent a group of genetic diseases in humans in which there is an impairment in one or more peroxisomal functions. The peroxisomal disorders are usually subdivided into two subgroups including (i) the peroxisome biogenesis disorders (PBDs) and (ii) the single peroxisomal (enzyme-) protein deficiencies. The PBD group is comprised of four different disorders including Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum's disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP). ZS, NALD, and IRD are clearly distinct from RCDP and are usually referred to as the Zellweger spectrum with ZS being the most severe and NALD and IRD the less severe disorders. Studies in the late 1980s had already shown that the PBD group is genetically heterogeneous with at least 12 distinct genetic groups as concluded from complementation studies. Thanks to the much improved knowledge about peroxisome biogenesis notably in yeasts and the successful extrapolation of this knowledge to humans, the genes responsible for all these complementation groups have been identified making molecular diagnosis of PBD patients feasible now. It is the purpose of this review to describe the current stage of knowledge about the clinical, biochemical, cellular, and molecular aspects of PBDs, and to provide guidelines for the post- and prenatal diagnosis of PBDs. Less progress has been made with respect to the pathophysiology and therapy of PBDs. The increasing availability of mouse models for these disorders is a major step forward in this respect.     

Nonsense and temperature-sensitive mutations in PEX13 are the cause of complementation group H of peroxisome biogenesis disorders.

Peroxisome biogenesis disorders, including Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease, are lethal hereditary diseases caused by abnormalities in peroxisomal assembly. To date, 12 genotypes have been identified. We now have evidence that the complete human cDNA encoding Pex13p, an SH3 protein of a docking factor for the peroxisome targeting signal 1 receptor (Pex5p), rescues peroxisomal matrix protein import and its assembly in fibroblasts from PBD patients of complementation group H. In addition, we detected mutations on the human PEX13 cDNA in two patients of group H. A severe phenotype of a ZS patient (H-02) was homozygous for a nonsense mutation, W234ter, which results in the loss of not only the SH3 domain but also the putative transmembrane domain of Pex13p. A more mildly affected NALD patient (H-01), whose fibroblasts showed the temperature-sensitive (TS) phenotype, was homozygous for a missense mutation in the SH3 domain of Pex13p, I326T. This mutant PEX13 cDNA expression in a PEX13-defective CHO mutant showed I326T to be a TS mutation and thus suggested that Pex13p with the I326T mutation in the SH3 domain is stable at 30 degrees C but is somewhat unstable at 37 degrees C.     

Identification of novel mutations in PEX2, PEX6, PEX10, PEX12, and PEX13 in Zellweger spectrum patients

Mutations in each of the 13 identified human PEX genes are known to cause a peroxisomal biogenesis defect (PBD). Affected patients can be divided into two broad clinical spectra: the Zellweger spectrum, which accounts for about 80% of PBD patients, and the rhizomelia chondrodysplasia punctata (RCDP) spectrum. The clinical continuum of Zellweger spectrum patients extends from Zellweger syndrome (ZS) as the prototype and the most severe entity of this group to neonatal adrenoleukodystrophy (NALD) as an intermediate form and infantile Refsum (IRD) disease as the mildest variant. Characteristic features of ZS patients are dysmorphic features, severe neurological impairment, liver dysfunction, and eye and skeletal abnormalities. Similar but less severe clinical signs are seen in patients with NALD and IRD. In this study ten clinically and/or biochemically well-characterized patients with classical ZS were investigated for defects in all known human PEX genes. We identified two novel mutations in PEX2 (official symbol, PXMP3), two novel mutations in PEX6, two novel mutations in PEX10, one novel mutation in PEX12, and one novel mutation in PEX13.     

Genetic heterogeneity of peroxisome biogenesis disorders among Japanese patients: evidence for a founder haplotype for the most common PEX10 gene mutation

We, as the only diagnostic center for peroxisome biogenesis disorders (PBD) in Japan, identified a total of 31 Japanese patients with PBD during the last 20 years. They were 27 patients with Zellweger syndrome (ZS), including two sib cases, three with neonatal adrenoleukodystrophy (NALD) and one with rhizomelic type chondrodysplasia punctata (RCDP). No patient with infantile Refsum disease has been detected. These patients were genetically subdivided into complementation group A (five ZS and one NALD), B (11 ZS), C (four ZS), E (five ZS and two NALD), F (two ZS), and R (one RCDP). They were subjected to mutation analysis of PEX1, PEX2, PEX6, PEX7, and PEX10. All the 11 ZS patients with group-B PBD had a common mutation, i.e., a homozygous 2-base-pair deletion in PEX10. To determine whether this highly frequent mutation is due to a founder effect, we analyzed single nucleotide polymorphisms within PEX10 among patients and Japanese controls. The mutation apparently arose once on an ancestral chromosome in the Japanese population. Based on the value of 24 PBD patients identified during the last 10 years, we estimated the prevalence of PBD in Japan to be approximately one in 500,000 births.     

PEX1 mutations in the Zellweger spectrum of the peroxisome biogenesis disorders

Diseases of the Zellweger spectrum represent a major subgroup of the peroxisome biogenesis disorders, a group of autosomal-recessive diseases that are characterized by widespread tissue pathology, including neurodegeneration. The Zellweger spectrum represents a clinical continuum, with Zellweger syndrome (ZS) having the most severe phenotype, and neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) having progressively milder phenotypes. Mutations in the PEX1 gene, which encodes a 143-kDa AAA ATPase protein required for peroxisome biogenesis, are the most common cause of the Zellweger spectrum diseases. The PEX1 mutations identified to date comprise insertions, deletions, nonsense, missense, and splice site mutations. Mutations that produce premature truncation codons (PTCs) are distributed throughout the PEX1 gene, whereas the majority of missense mutations segregate with the two essential AAA domains of the PEX1 protein. Severity at the two ends of the Zellweger spectrum correlates broadly with mutation type and impact (i.e., the severe ZS correlates with PTCs on both alleles, and the milder phenotypes correlate with missense mutations), but exceptions to these general correlations exist. This article provides an overview of the currently known PEX1 mutations, and includes, when necessary, revised mutation nomenclature and genotype-phenotype correlations that may be useful for clinical diagnosis.     

Genotype-phenotype correlations in disorders of peroxisome biogenesis.

Genetically determined human peroxisomal disorders are subdivided into two major categories: disorders of peroxisome biogenesis (PBD), in which the organelle is not formed normally, and those that involve a single peroxisomal enzyme. Twelve PBD have been identified, and the molecular defects have been defined in 10. All involve defects in the import of proteins into the organelle. Factors required for this import are now referred to as peroxins (PEX) and form the basis of a new and preferred classification system. The PBD are associated with four clinical phenotypes, named before their association with the organelle was recognized: Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP). The first three are associated with 9 of the 10 PEX defects that have been defined so far, and represent a clinical continuum with variant severity, with ZS the most severe, NALD intermediate, and IRD the least severe. RCDP is associated with PEX7. Genotype-phenotype correlations are complicated by the fact that the clinical manifestations of the ZS-NALD-IRD continuum can be mimicked by disorders that affect single enzymes of peroxisomal fatty acid oxidation, and PEX7 by disorders of plasmalogen synthesis enzymes. Furthermore, clinical manifestations of each of the PEX disorders may vary. Phenotypic expression varies with the nature of the mutation, the milder phenotypes being associated with mutations that do not abolish function completely, or with mosaicism. Definition of the molecular defects is of great value for genetic counseling and may be of aid in establishing prognosis.     

The peroxin Pex6p gene is impaired in peroxisomal biogenesis disorders of complementation group 6

Human genetic peroxisomal biogenesis disorders (PBDs), such as Zellweger syndrome, comprise 13 different complementation groups (CGs). Eleven peroxin genes, termed PEXs, responsible for PBDs have been identified, whereas pathogenic genes for PBDs of 2 CGs, CG-A (the same CG as CG8 in the United States and Europe) and CG6, remained unidentified. We herein provide several lines of novel evidence indicating that PEX6, the pathogenic gene for CG4, is impaired in PBD of CG6. Expression of PEX6 restored peroxisome assembly in fibroblasts from a CG6 PBD patient. This patient was a compound heterozygote for PEX6 gene alleles. Accordingly, by merging CG6 with CG4, human PBDs are now classified into 12 CGs. Received: December 25, 2000 / Accepted: February 5, 2001     

Pathology of hepatic peroxisomes and mitochondria in patients with peroxisomal disorders

Summary The morphology of hepatic peroxisomes in five patients with metabolic disorders believed to be due to inherited defects of peroxisomal function or biogenesis is described. Electron microscopy and cytochemical staining for catalase were used to identify peroxisomes in two boys with infantile Refsum's disease (IRD), a girl with autopsy confirmed neonatal adrenoleukodystrophy (NALD), and two boys with pseudo-Zellweger syndrome (PZS). In the patients with IRD and NALD hepatic peroxisomes were significantly reduced in size and number and contained electron dense centres. In the liver of the patients with PZS the peroxisomes were enlarged. Morphologically abnormal peroxisomes were also detected in autopsy tissue from one boy with PZS using electron microscopy. Lamellar-lipid inclusions and mitochondria with crystalline inclusions and/or abnormal cristae are also described in two patients, one with IRD, the other with NALD.     

Complementation analysis in patients with the clinical phenotype of a generalised peroxisomal disorder.

The generalised peroxisomal disorders (GPDs) Zellweger syndrome (ZS), neonatal adrenoleucodystrophy (NALD), and infantile Refsum's disease (IRD) are autosomal recessive disorders associated with a failure to assemble mature peroxisomes. We confirmed the diagnosis of a GPD in eight ZS and four IRD patients (GPD1 to GPD12) biochemically by measuring very long chain fatty acids, plasmalogen biosynthesis, and catalase solubility in skin fibroblasts. One further patient (BOX-1) had the clinical phenotype of ZS, but biochemical investigations indicated an isolated deficiency of peroxisomal beta oxidation. To date a total of 10 complementation groups (CGs) for the GPDs and three further CGs for isolated beta oxidation deficiencies have been identified. Most GPD patients have been shown to belong to CG-1 (Baltimore classification); among the rarer groups, CG-4 and CG-8 predominate. We performed somatic cell hybridisation experiments on strains GPD-1 to GPD-12 using plasmalogen biosynthesis as a marker for correction and found that six ZS and three IRD patients, eight of whom were of UK origin, belonged to CG-1. Strain GPD-11, a patient of UK origin with an unusual biochemical phenotype, belonged to CG-8. Strains GPD-10 and GPD-12 were derived from ZS patients of Arabian and Pakistani origin and belonged to the rarer CGs 2 and 7, respectively. Furthermore, complementation analysis using beta oxidation as a marker showed that BOX-1 had an isolated deficiency of the bifunctional protein.     

The Pex1-G844D mouse: A model for mild human Zellweger spectrum disorder

Zellweger spectrum disorder (ZSD) is a disease continuum that results from inherited defects in PEX genes essential for normal peroxisome assembly. These autosomal recessive disorders impact brain development and also cause postnatal liver, adrenal, and kidney dysfunction, as well as loss of vision and hearing. The hypomorphic PEX1-G843D missense allele, observed in approximately 30% of ZSD patients, is associated with milder clinical and biochemical phenotypes, with some homozygous individuals surviving into early adulthood. Nonetheless, affected children with the PEX1-G843D allele have intellectual disability, failure to thrive, and significant sensory deficits. To enhance our ability to test candidate therapies that improve human PEX1-G843D function, we created the novel Pex1-G844D knock-in mouse model that represents the murine equivalent of the common human mutation. We show that Pex1-G844D homozygous mice recapitulate many classic features of mild ZSD cases, including growth retardation and fatty livers with cholestasis. In addition, electrophysiology, histology, and gene expression studies provide evidence that these animals develop a retinopathy similar to that observed in human patients, with evidence of cone photoreceptor cell death. Similar to skin fibroblasts obtained from ZSD patients with a PEX1-G843D allele, we demonstrate that murine cells homozygous for the Pex1-G844D allele respond to chaperone-like compounds, which normalizes peroxisomal β-oxidation. Thus, the Pex1-G844D mouse provides a powerful model system for testing candidate therapies that address the most common genetic cause of ZSD. In addition, this murine model will enhance studies focused on mechanisms of pathogenesis.     

Defective PEX gene products correlate with the protein import, biochemical abnormalities, and phenotypic heterogeneity in peroxisome biogenesis disorders.

Peroxisome biogenesis disorders (PBD) comprise three phenotypes including Zellweger syndrome (ZS) (the most severe), neonatal adrenoleucodystrophy, and infantile Refsum disease (IRD) (the most mild), and can be classified into at least 12 genetic complementation groups, which are not predictive of the phenotypes. Several pathogenic genes for PBD groups have been identified, but the relationship between the defective gene products and phenotypic heterogeneity has remained unclear. We identified a mutation in the PEX2 gene in an IRD patient with compound heterozygosity for a missense mutation and the known nonsense mutation detected in ZS patients. In transfection experiments using the peroxisome deficient CHO mutant, Z65 with a nonsense mutation in the PEX2 gene, we noted the E55K mutation had mosaic activities of peroxisomal protein import machinery and residual activities of peroxisomal functions, including dihydroxyacetone phosphate acyltransferase and beta oxidation of very long chain fatty acids. The nonsense mutation severely affects these peroxisomal functions as well as the protein import. These data suggest that allelic heterogeneity of the PEX gene affects the peroxisomal protein import and functions and regulates the clinical severity in PBD.     

Genetic and clinical aspects of Zellweger spectrum patients with PEX1 mutations

Objective: To analyse the PEX1 gene, the most common cause for peroxisome biogenesis disorders (PBD), in a consecutive series of patients with Zellweger spectrum. Methods: Mutations were detected by different methods including SSCP analyses as a screening technique on the basis of genomic or cDNA, followed by direct sequencing of PCR fragments with an abnormal electrophoresis pattern. Results: 33 patients were studied. Two common mutations, c.2528G→A, G843D and c.2098_2098insT, I700YfsX42, accounted for over 80% of all abnormal PEX1 alleles, emphasising their diagnostic relevance. Most PEX1 mutations were distributed over the two AAA cassettes with the two functional protein domains, D1 and D2, and the highly conserved Walker motifs. Phenotypic severity of Zellweger spectrum in CG1 depended on the effect of the mutation on the PEX1 protein, peroxin 1. PEX1 mutations could be divided into two classes of genotype–phenotype correlation: class I mutations led to residual PEX1 protein levels and function and a milder phenotype; class II mutations almost abolished PEX1 protein levels and function, resulting in a severe phenotype. Compound heterozygote patients for a class I and class II mutation had an intermediate phenotype. Conclusions: Molecular confirmation of the clinical and biochemical diagnosis will allow the prediction of the clinical course of disease in individual PBD cases.     

Phenotype-genotype relationships in PEX10-deficient peroxisome biogenesis disorder patients

The peroxisome biogenesis disorders (PBD) are characterized by neural, hepatic, and renal deficiencies, severe mental retardation, and are often lethal. These disorders are genetically and phenotypically heterogeneous and are caused by defective peroxisomal protein import and decreased peroxisomal metabolic function. Mutations in PEX10 have been identified in patients from complementation group 7 (CG7) of the PBDs and we report here an analysis of the genotypes and phenotypes of PEX10-deficient patients. All four PEX10-deficient Zellweger Syndrome (ZS) patients were found to have nonsense, frameshift, or splice site mutations that remove large portions of the PEX10 coding region. In contrast, a more mildly affected PEX10-deficient neonatal adrenoleukodystrophy patient expressed a PEX10 allele with a missense mutation, H290Q, affecting the C-terminal zinc-binding domain of the PEX10 product. These results support the hypothesis that severe, loss-of-function mutations in PEX genes cause more severe clinical phenotypes, whereas mildly affected PBD patients have PEX gene mutations that retain residual function. To quantitate the effects of the PEX10 mutations identified here and elsewhere we employed a functional complementation assay. Surprisingly, we observed that nonsense and frameshift mutations predicted to delete the C-terminal 2/3 (R125X) or 1/3 (c.704insA) of the protein displayed nearly normal PEX10 activity. Even more surprising, we found that the unexpectedly high PEX10 activity displayed by these cDNAs could be eliminated by removing or mutating segments of the PEX10 cDNA downstream of the mutations. Although these results demonstrate serious flaws in the PEX10 functional complementation assay, they do suggest that the C-terminal zinc-binding domain is critical for PEX10 function.     

Morphometry of peroxisomes and immunolocalisation of peroxisomal proteins in the liver of patients with generalised peroxisomal disorders

Hepatic peroxisomes were studied by morphometric and immunocytochemical techniques in control patients and in four Zellweger syndrome patients, two infantile Refsum's (IRD) patients, one neonatal adrenoleukodystrophy (NALD) patient, and three patients with peroxisomal disorders (PD) which do not fit any currently recognised classification, but have disorders involving a defect in peroxisomal biogenesis. Peroxisomes which were ultrastructurally abnormal and greatly reduced in size and/or number were found in two of the Zellweger syndrome patients, and the NALD and IRD patients. There was variation in their numerical density ranging from none at all in two of the Zellweger syndrome patients to normal numbers in the IRD patients. In most patients there was a decrease in the immunolabelling of catalase over the peroxisomes. In the Zellweger syndrome and NALD patients, the small, abnormal peroxisomes did not label for any of the -oxidation proteins. The IRD patients and the PD patients however, were heterogeneous with respect to -oxidation labelling. The ultrastructural heterogenity of peroxisomes in these peroxisomal disorders patients indicates there may be genotypic differences between the major groups and also within each group. The common factor in all the patients in this study where peroxisomes were present was the presence in the hepatic peroxisomes of an electron dense centre which did not label immunocytochemically for catalase or the -oxidation enzymes. This electron dense centre may indicate a structural abnormality in the peroxisomes in these patients.     

Two novel PEX1 mutations in a patient with Zellweger syndrome: the first Korean case confirmed by biochemical, and molecular evidence

Peroxisome biogenesis disorders (PBD) represent a spectrum of genetic disorders characterized by impaired peroxisome assembly. Zellweger syndrome (ZS) is the most severe form of PBD and is characterized by craniofacial abnormalities, severe hypotonia, neonatal seizures, ocular abnormalities, psychomotor retardation, hepatomegaly and increased levels of very long chain fatty acids (VLCFA). The most common mutation associated with the PBD is PEX1. Here, the first Korean patient with ZS confirmed by clinical, biochemical, and molecular findings is reported. Two novel mutations of the PEX1 gene were identified in the patient with ZS. The patient was a compound heterozygote for c.2034_2035delCA and c.2845C>T mutations of the PEX1 gene. Both mutations are novel findings and were inherited from the patient's parents. In summary, here the first Korean case of ZS is reported that was confirmed by two novel mutations of the PEX1 gene.