👪

Inheritance

1

Autosomal recessive inheritance HP:0000007

All Zellweger spectrum disorders are inherited as autosomal recessive traits, requiring biallelic pathogenic variants in a single PEX gene.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:14527301 SUPPORT Human Clinical

"The peroxisome biogenesis disorders (PBDs) comprise 12 autosomal recessive complementation groups (CGs)."

This review directly supports autosomal recessive inheritance of peroxisome biogenesis disorders, the parent class containing ZSD.

◆

Subtypes

3

Zellweger Syndrome (cerebro-hepato-renal syndrome)

The most severe phenotype, presenting in the neonatal period with profound hypotonia, intractable seizures, characteristic craniofacial dysmorphism, severe liver disease, and renal cortical cysts. Most affected infants die in the first year of life.

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Infants with severe ZSD are significantly impaired and typically die during the first year of life, usually having made no developmental progress."

GeneReviews supports the severe-end (classic Zellweger) phenotype with profound impairment and first-year mortality.

Neonatal Adrenoleukodystrophy

Intermediate-severity phenotype with neonatal hypotonia, developmental delay, progressive leukodystrophy, adrenocortical dysfunction, and longer survival into childhood than classic Zellweger syndrome.

Show evidence (1 reference)

PMID:11769739 SUPPORT Human Clinical

"There is phenotypic and genetic overlap among the PBD known as Zellweger syndrome (ZS), infantile Refsum disease (IRD), and neonatal adrenoleukodystrophy (NALD)."

This reference establishes NALD as a recognized intermediate phenotype on the Zellweger continuum.

Infantile Refsum Disease

The mildest end of the spectrum, with later onset, slower progression, retinitis pigmentosa, sensorineural hearing loss, ataxia, and survival into adolescence or adulthood. Distinct from adult (PHYH-related) Refsum disease.

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Individuals with intermediate/milder ZSD do not have congenital malformations, but rather progressive peroxisome dysfunction variably manifest as sensory loss (secondary to retinal dystrophy and sensorineural hearing loss), neurologic involvement (ataxia, polyneuropathy, and leukodystrophy),..."

GeneReviews supports the milder IRD-end ZSD phenotype with progressive sensory, neurologic, hepatic, and adrenal involvement.

⚙

Pathophysiology

4

Peroxisome Biogenesis Failure

Biallelic loss-of-function variants in PEX genes (peroxins) disrupt peroxisome assembly, matrix protein import, or membrane biogenesis. The result is absent or empty "ghost" peroxisomes incapable of carrying out peroxisomal metabolism.

PEX1 hgnc:8850 PEX6 hgnc:8859 PEX12 hgnc:8854

peroxisome organization GO:0007031 ↓ DECREASED protein import into peroxisome matrix GO:0016558 ↓ DECREASED

peroxisome GO:0005777

Downstream

VLCFA and Branched-Chain Fatty Acid Accumulation Without functional peroxisomes, peroxisomal beta- and alpha-oxidation pathways fail, allowing VLCFA, phytanic acid, and pristanic acid to accumulate in plasma and tissues.

Plasmalogen and Bile Acid Intermediate Imbalance Loss of peroxisomal ether-lipid synthesis depletes plasmalogens, while blocked bile acid side-chain shortening leads to accumulation of C27 bile acid intermediates (DHCA, THCA).

Show evidence (2 references)

PMID:17055079 SUPPORT Human Clinical

"Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD)."

This review directly supports PEX-gene-mediated peroxisome assembly failure as the molecular basis of ZSD.

PMID:27941306 SUPPORT In Vitro

"Peroxisome is a single-membrane-bounded ubiquitous organelle containing a hundred different enzymes that catalyze various metabolic pathways"

Fujiki's CHO cell-mutant complementation review supports the role of peroxisomes as multifunctional metabolic organelles whose biogenesis failure underlies ZSD.

VLCFA and Branched-Chain Fatty Acid Accumulation

Defective peroxisomal beta-oxidation causes pathologic elevations of saturated very long-chain fatty acids (C26:0) and the branched-chain fatty acids phytanic and pristanic acid in plasma, fibroblasts, and tissues, providing the principal biochemical diagnostic signature.

very long-chain fatty acid metabolic process GO:0000038 ↓ DECREASED fatty acid beta-oxidation GO:0006635 ↓ DECREASED fatty acid alpha-oxidation GO:0001561 ↓ DECREASED

Downstream

Multi-System Clinical Phenotype Accumulated lipid species and absent peroxisomal products contribute to neuronal migration defects, demyelination, hepatic dysfunction, renal cysts, and craniofacial abnormalities.

Very-long-chain fatty acids Impaired peroxisomal beta-oxidation is measured clinically as elevated plasma very-long-chain fatty acids.

Phytanic acid Impaired peroxisomal alpha-oxidation can elevate plasma phytanic acid.

Show evidence (2 references)

PMID:29282281 SUPPORT Model Organism

"We generated Pex19 Drosophila mutants, which recapitulate the hallmarks of PBDs, like absence of peroxisomes, reduced viability, neurodegeneration, mitochondrial abnormalities, and accumulation of VLCFAs."

Drosophila Pex19 model recapitulates VLCFA accumulation, the defining biochemical signature of ZSD.

PMID:36649687 SUPPORT Human Clinical

"PDs are characterized by abnormal elevations of very-long-chain fatty acids (VLCFA)."

Clinical case series confirms VLCFA elevation as the defining biochemical feature of peroxisomal disorders including ZSD.

Plasmalogen and Bile Acid Intermediate Imbalance

Loss of peroxisomal ether-phospholipid synthesis depletes red blood cell and tissue plasmalogens, while blocked bile acid side-chain shortening produces accumulation of dihydroxycholestanoic acid (DHCA) and trihydroxycholestanoic acid (THCA). Plasmalogen deficiency is implicated in CNS myelin instability.

ether lipid biosynthetic process GO:0008611 ↓ DECREASED bile acid metabolic process GO:0008206 ↓ DECREASED

Downstream

Multi-System Clinical Phenotype Plasmalogen deficiency contributes to dysmyelination and neurologic dysfunction; accumulated bile acid intermediates contribute to cholestatic liver disease.

Plasmalogens Impaired peroxisomal ether-lipid biosynthesis lowers erythrocyte and tissue plasmalogens.

C27 bile acid intermediates (DHCA, THCA) Blocked peroxisomal bile-acid side-chain shortening leads to accumulation of abnormal C27 bile-acid intermediates.

Show evidence (1 reference)

PMID:34628380 SUPPORT Human Clinical

"it is worth investigating the level of long-chain fatty acids, plasmalogen of erythrocytes, intermediate metabolites of bile acid synthesis, or carrying out genetic sequencing."

Clinical case report supports erythrocyte plasmalogen depletion and bile acid intermediate accumulation as biochemical hallmarks of ZSD.

Multi-System Clinical Phenotype

Combined toxic accumulation and product deficiency produce the characteristic Zellweger phenotype: profound hypotonia, intractable seizures, craniofacial dysmorphism, leukodystrophy, hepatic dysfunction, renal cortical cysts, and progressive sensory loss.

Downstream

Neonatal Hypotonia The severe neonatal ZSD presentation includes hypotonia as an early neuromuscular manifestation of peroxisome biogenesis failure.

Feeding Difficulties Severe neonatal ZSD often causes poor feeding, linking the multisystem neonatal phenotype to nutritional compromise.

Seizures Congenital neuronal migration defects in severe ZSD produce neonatal-onset seizures.

Characteristic Craniofacial Features Severe ZSD includes distinctive craniofacial dysmorphism as part of the congenital malformation spectrum.

Hepatomegaly Peroxisomal bile-acid and lipid metabolism failure manifests clinically as liver involvement, including hepatomegaly, in severe and milder ZSD.

Renal Cysts Severe ZSD includes renal cysts among the congenital malformations associated with peroxisome biogenesis failure.

Chondrodysplasia Punctata Severe ZSD includes bony stippling of the patellae and long bones, captured clinically as chondrodysplasia punctata.

Sensorineural Hearing Loss Progressive peroxisome dysfunction causes sensory loss that includes sensorineural hearing impairment.

Retinitis Pigmentosa Progressive peroxisome dysfunction causes retinal dystrophy, represented in the pathograph as retinal degeneration/retinitis pigmentosa.

Leukodystrophy Progressive peroxisome dysfunction causes neurologic involvement that includes leukodystrophy.

Ataxia Progressive neurologic involvement in intermediate/milder ZSD includes ataxia.

Polyneuropathy Progressive neurologic involvement in intermediate/milder ZSD includes polyneuropathy.

Developmental Delay The neurologic impact of ZSD commonly includes developmental delay, although intellect can be normal at the mildest end.

Adrenal Insufficiency Progressive peroxisome dysfunction includes adrenal insufficiency, particularly in milder ZSD presentations.

Nephrolithiasis Progressive peroxisome dysfunction can include renal oxalate stones.

Osteopenia Some individuals with ZSD have reduced bone mineral density.

Amelogenesis Imperfecta Dental enamel involvement in secondary teeth is a common ZSD manifestation.

Show evidence (2 references)

PMID:20301621 SUPPORT Human Clinical

"Affected newborns are hypotonic and feed poorly."

GeneReviews directly supports the early multi-system clinical presentation of severe ZSD.

PMID:15868469 SUPPORT Model Organism

"Peroxisome biogenesis disorders, of which Zellweger syndrome is the most severe, result in severe neurological dysfunction associated with abnormal CNS neuronal migrations due to the lack of functional peroxisomes."

PEX2 mouse model supports neuronal migration defects as a core neurodevelopmental consequence of peroxisome deficiency.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

18

Digestive 2

Feeding Difficulties Feeding difficulties HP:0011968

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Affected newborns are hypotonic and feed poorly."

GeneReviews directly supports poor feeding in affected newborns.

Hepatomegaly Hepatomegaly HP:0002240

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"liver disease that can be severe"

GeneReviews supports hepatic disease as a major organ-system phenotype of severe ZSD.

Ear 1

Sensorineural Hearing Loss Sensorineural hearing impairment HP:0000407

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"sensory loss (secondary to retinal dystrophy and sensorineural hearing loss)"

GeneReviews supports sensorineural hearing loss as a recognized progressive sensory phenotype of milder ZSD.

Endocrine 1

Adrenal Insufficiency Adrenal insufficiency HP:0000846

Show evidence (1 reference)

PMID:25179809 SUPPORT Human Clinical

"Primary adrenal insufficiency was found in 7/24 patients examined, with 4/7 being asymptomatic."

Clinical cohort study supports adrenal insufficiency as a frequent and often asymptomatic phenotype in ZSD.

Eye 1

Cataract OCCASIONAL Cataract HP:0000518

Show evidence (1 reference)

PMID:33335840 SUPPORT Human Clinical

"Cataracts were reported by 18% and 14% of caregivers of living and deceased individuals, respectively."

Caregiver-reported cross-sectional study documents cataracts as a recurrent ophthalmologic feature across the ZSD spectrum.

Genitourinary 2

Renal Cysts Renal cyst HP:0000107

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"neuronal migration defects associated with neonatal-onset seizures, renal cysts, and bony stippling"

GeneReviews supports renal cortical cysts as a characteristic congenital malformation of severe ZSD.

Nephrolithiasis Nephrolithiasis HP:0000787

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"liver dysfunction, adrenal insufficiency, and renal oxalate stones."

GeneReviews directly lists renal oxalate stones in ZSD.

Head and Neck 2

Characteristic Craniofacial Features Abnormal facial shape HP:0001999

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"They have distinctive facies"

GeneReviews supports distinctive facial features as a hallmark of severe ZSD.

Amelogenesis Imperfecta Amelogenesis imperfecta HP:0000705

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Some have osteopenia; almost all have ameleogenesis imperfecta in the secondary teeth."

GeneReviews supports amelogenesis imperfecta of secondary teeth.

Musculoskeletal 2

Neonatal Hypotonia Hypotonia HP:0001252

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Affected newborns are hypotonic and feed poorly."

GeneReviews directly supports neonatal hypotonia as a defining presenting feature of ZSD.

Osteopenia Osteopenia HP:0000938

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"Some have osteopenia; almost all have ameleogenesis imperfecta in the secondary teeth."

GeneReviews supports osteopenia in some individuals with ZSD.

Nervous System 4

Seizures Seizure HP:0001250

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"neuronal migration defects associated with neonatal-onset seizures"

GeneReviews supports neonatal-onset seizures as a characteristic congenital malformation phenotype of severe ZSD.

Leukodystrophy Leukodystrophy HP:0002415

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)"

GeneReviews supports leukodystrophy as a major progressive neurologic phenotype of milder ZSD.

Developmental Delay Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"While hypotonia and developmental delays are typical, intellect can be normal."

GeneReviews supports developmental delay as a typical neurodevelopmental phenotype across the ZSD spectrum.

Ataxia Ataxia HP:0001251

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)"

GeneReviews directly lists ataxia in intermediate/milder ZSD.

Other 3

Retinitis Pigmentosa Retinal degeneration HP:0000546

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"sensory loss (secondary to retinal dystrophy and sensorineural hearing loss)"

GeneReviews supports retinal dystrophy as a key sensory phenotype in milder ZSD.

Chondrodysplasia Punctata Epiphyseal stippling HP:0010655

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"renal cysts, and bony stippling"

GeneReviews supports chondrodysplasia punctata (epiphyseal stippling) as a characteristic congenital skeletal malformation of severe ZSD.

Polyneuropathy Polyneuropathy HP:0001271

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)"

GeneReviews directly lists polyneuropathy in intermediate/milder ZSD.

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Genetic Associations

3

PEX1 (Autosomal recessive causal pathogenic variant; PEX1 is the most common cause of ZSD. Specific PEX1 variants in exon 13 are associated with primary adrenal insufficiency.)

Gene: PEX1 hgnc:8850

Show evidence (1 reference)

PMID:36649687 SUPPORT Human Clinical

"all the 3 patients with PBD and adrenal insufficiency who were on steroid supplementation had the compound heterozygous pathogenic variant in exon 13 of PEX1"

Clinical case series supports a specific PEX1 compound-heterozygous genotype as causal for ZSD with adrenal insufficiency.

PEX6 (Autosomal recessive causal pathogenic variant; PEX6 variants are a recognized cause of Zellweger syndrome, often associated with severe phenotypes when leading to truncation.)

Gene: PEX6 hgnc:8859

Show evidence (1 reference)

PMID:10408779 SUPPORT Human Clinical

"Most of the mutations led to premature termination or large deletions of the PEX6 protein and resulted in the most severe peroxisome biogenesis disorder phenotype of Zellweger syndrome."

Direct sequencing study supports PEX6 truncating mutations as causal for the most severe Zellweger phenotype.

PEX12 (Autosomal recessive causal pathogenic variant in the ZSD spectrum.)

Gene: PEX12 hgnc:8854

Show evidence (1 reference)

PMID:17055079 SUPPORT Human Clinical

"DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD."

Steinberg review supports the multi-gene PEX-based architecture of the ZSD/ZSS spectrum, in which PEX12 is one of the recognized causal genes.

💊

Medical Actions

3

Supportive Care

Action: Supportive Care NCIT:C15747

There is no curative therapy for Zellweger spectrum disorders. Care is multidisciplinary and supportive, addressing seizures, feeding, hepatic dysfunction, hearing, and vision.

Target Phenotypes: Feeding difficulties HP:0011968 Sensorineural hearing impairment HP:0000407 Retinal degeneration HP:0000546 Cataract HP:0000518 Seizure HP:0001250 Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"The focus is on symptomatic therapy and may include gastrostomy to provide adequate calories, hearing aids, cataract removal, glasses to correct refractive errors, supplementation of fat-soluble vitamins, and cholic acid supplementation"

GeneReviews supports symptomatic/supportive management as the standard of care across the ZSD spectrum.

Adrenal Replacement Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: hydrocortisone CHEBI:17650

Patients with documented primary adrenal insufficiency with ZSD receive glucocorticoid (and sometimes mineralocorticoid) replacement.

Target Phenotypes: Adrenal insufficiency HP:0000846

Show evidence (2 references)

PMID:25179809 SUPPORT Human Clinical

"It is important to detect impaired adrenal function because it has treatment implications."

Clinical cohort study supports systematic adrenal-function screening and replacement therapy as a treatment-relevant intervention in ZSD.

PMID:36649687 SUPPORT Human Clinical

"Three patients were on daily hydrocortisone replacement, and 1 patient was on stress-dose hydrocortisone only as needed."

Peroxisomal-disorder case series directly documents hydrocortisone replacement in patients with adrenal insufficiency.

Cholic Acid Supplementation

Action: Pharmacotherapy NCIT:C15986

Agent: cholic acid CHEBI:16359

Oral cholic acid supplementation is used as part of symptomatic management for ZSD, where peroxisomal bile acid synthesis is disrupted and C27 bile acid intermediates accumulate.

Mechanism Target:

MODULATES Plasmalogen and Bile Acid Intermediate Imbalance — Cholic acid supplementation is linked to the bile-acid-intermediate branch of peroxisomal metabolic dysfunction.

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"supplementation of fat-soluble vitamins, and cholic acid supplementation"

GeneReviews lists cholic acid supplementation in ZSD management.

Show evidence (1 reference)

PMID:20301621 SUPPORT Human Clinical

"supplementation of fat-soluble vitamins, and cholic acid supplementation"

GeneReviews directly supports cholic acid supplementation as a treatment used in the symptomatic management of ZSD.

🔬

Biochemical Markers

4

Very-long-chain fatty acids (Increased)

Context: Elevated plasma VLCFA (C26:0) is the principal biochemical screening test for Zellweger spectrum disorders.

Pathograph Readouts

Readout Of VLCFA and Branched-Chain Fatty Acid Accumulation Positive Diagnostic

Increased plasma VLCFA directly reports the peroxisomal VLCFA beta-oxidation block.

Show evidence (1 reference)

PMID:36649687 SUPPORT Human Clinical

"PDs are characterized by abnormal elevations of very-long-chain fatty acids (VLCFA)."

Supports VLCFA elevation as the defining biochemical abnormality across peroxisomal disorders including ZSD.

Phytanic acid (Increased)

Context: Phytanic acid accumulates due to impaired peroxisomal alpha-oxidation.

Pathograph Readouts

Readout Of VLCFA and Branched-Chain Fatty Acid Accumulation Positive Diagnostic

Elevated phytanic acid reports impaired peroxisomal branched-chain fatty acid catabolism within the same lipid-metabolism failure branch.

Show evidence (1 reference)

PMID:3119940 SUPPORT Human Clinical

"plasma phytanic acid concentrations may be elevated."

Biochemical diagnostic review supports elevated phytanic acid as a Zellweger biochemical abnormality.

Plasmalogens (Decreased)

Context: Erythrocyte plasmalogens are reduced because peroxisomal ether-lipid synthesis is impaired.

Pathograph Readouts

Readout Of Plasmalogen and Bile Acid Intermediate Imbalance Negative Diagnostic

Decreased red blood cell plasmalogens report failure of peroxisomal ether-lipid synthesis.

Show evidence (1 reference)

PMID:36914043 SUPPORT Human Clinical

"Markedly reduced plasmalogens are a classic feature of peroxisome biogenesis disorders (PBD) because plasmalogen synthesis requires functional peroxisomes."

Clinical laboratory study supports reduced plasmalogens as a classic biochemical feature of peroxisome biogenesis disorders.

C27 bile acid intermediates (DHCA, THCA) (Increased)

Context: Dihydroxycholestanoic and trihydroxycholestanoic acids accumulate because peroxisomal side-chain shortening of cholesterol-derived bile acid precursors is blocked.

Pathograph Readouts

Readout Of Plasmalogen and Bile Acid Intermediate Imbalance Positive Diagnostic

Increased C27 bile acid intermediates report impaired peroxisomal bile acid side-chain shortening.

Show evidence (1 reference)

PMID:3119940 SUPPORT Human Clinical

"abnormal C27-bile acids, very long chain fatty acids, dicarboxylic acids and pipecolic acid accumulate in the plasma of the patients."

Biochemical diagnostic review supports C27 bile acid accumulation as a plasma abnormality in classic Zellweger syndrome.

{ }

Source YAML

click to show

name: Zellweger Spectrum Disorders
creation_date: "2026-05-13T00:00:00Z"
updated_date: "2026-05-21T10:52:42Z"
category: Mendelian
description: >-
  Zellweger spectrum disorders (ZSD) are a continuum of autosomal recessive
  peroxisome biogenesis disorders caused by biallelic pathogenic variants in
  any of at least 13 PEX genes, most commonly PEX1, PEX6, and PEX12. Defective
  peroxisome assembly produces multi-system metabolic failure characterized by
  plasma accumulation of very long-chain fatty acids (VLCFA), branched-chain
  fatty acids, and bile acid intermediates, together with deficiency of ether
  phospholipids (plasmalogens). The clinical spectrum spans severe neonatal
  Zellweger syndrome (cerebro-hepato-renal syndrome) at one end, intermediate
  neonatal adrenoleukodystrophy (NALD), and the milder infantile Refsum
  disease (IRD) at the other; severity correlates with residual peroxisomal
  function. Affected individuals typically present with profound hypotonia,
  seizures, characteristic craniofacial features, hepatic dysfunction, and
  variable progressive neurological, ophthalmologic, and auditory impairment.
disease_term:
  preferred_term: Zellweger spectrum disorders
  term:
    id: MONDO:0019609
    label: Zellweger spectrum disorders
synonyms:
- Peroxisome biogenesis disorder, Zellweger spectrum
- ZSD
- PBD-ZSS
parents:
- peroxisome biogenesis disorder
- inborn errors of metabolism
has_subtypes:
- name: Zellweger Syndrome
  display_name: Zellweger Syndrome (cerebro-hepato-renal syndrome)
  description: >-
    The most severe phenotype, presenting in the neonatal period with profound
    hypotonia, intractable seizures, characteristic craniofacial dysmorphism,
    severe liver disease, and renal cortical cysts. Most affected infants die
    in the first year of life.
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Infants with severe ZSD are significantly impaired and typically die
      during the first year of life, usually having made no developmental
      progress.
    explanation: >-
      GeneReviews supports the severe-end (classic Zellweger) phenotype with
      profound impairment and first-year mortality.
- name: NALD
  display_name: Neonatal Adrenoleukodystrophy
  description: >-
    Intermediate-severity phenotype with neonatal hypotonia, developmental
    delay, progressive leukodystrophy, adrenocortical dysfunction, and longer
    survival into childhood than classic Zellweger syndrome.
  evidence:
  - reference: PMID:11769739
    reference_title: Late onset white matter disease in peroxisome biogenesis disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      There is phenotypic and genetic overlap among the PBD known as
      Zellweger syndrome (ZS), infantile Refsum disease (IRD), and neonatal
      adrenoleukodystrophy (NALD).
    explanation: >-
      This reference establishes NALD as a recognized intermediate
      phenotype on the Zellweger continuum.
- name: IRD
  display_name: Infantile Refsum Disease
  description: >-
    The mildest end of the spectrum, with later onset, slower progression,
    retinitis pigmentosa, sensorineural hearing loss, ataxia, and survival
    into adolescence or adulthood. Distinct from adult (PHYH-related) Refsum
    disease.
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with intermediate/milder ZSD do not have congenital
      malformations, but rather progressive peroxisome dysfunction variably
      manifest as sensory loss (secondary to retinal dystrophy and
      sensorineural hearing loss), neurologic involvement (ataxia,
      polyneuropathy, and leukodystrophy), liver dysfunction, adrenal
      insufficiency, and renal oxalate stones.
    explanation: >-
      GeneReviews supports the milder IRD-end ZSD phenotype with progressive
      sensory, neurologic, hepatic, and adrenal involvement.
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    All Zellweger spectrum disorders are inherited as autosomal recessive
    traits, requiring biallelic pathogenic variants in a single PEX gene.
  evidence:
  - reference: PMID:14527301
    reference_title: Peroxisome biogenesis disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The peroxisome biogenesis disorders (PBDs) comprise 12 autosomal
      recessive complementation groups (CGs).
    explanation: >-
      This review directly supports autosomal recessive inheritance of
      peroxisome biogenesis disorders, the parent class containing ZSD.
pathophysiology:
- name: Peroxisome Biogenesis Failure
  description: >-
    Biallelic loss-of-function variants in PEX genes (peroxins) disrupt
    peroxisome assembly, matrix protein import, or membrane biogenesis. The
    result is absent or empty "ghost" peroxisomes incapable of carrying out
    peroxisomal metabolism.
  genes:
  - preferred_term: PEX1
    term:
      id: hgnc:8850
      label: PEX1
  - preferred_term: PEX6
    term:
      id: hgnc:8859
      label: PEX6
  - preferred_term: PEX12
    term:
      id: hgnc:8854
      label: PEX12
  biological_processes:
  - preferred_term: peroxisome organization
    term:
      id: GO:0007031
      label: peroxisome organization
    modifier: DECREASED
  - preferred_term: protein import into peroxisome matrix
    term:
      id: GO:0016558
      label: protein import into peroxisome matrix
    modifier: DECREASED
  cellular_components:
  - preferred_term: peroxisome
    term:
      id: GO:0005777
      label: peroxisome
  evidence:
  - reference: PMID:17055079
    reference_title: Peroxisome biogenesis disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Defects in PEX genes impair peroxisome assembly and multiple metabolic
      pathways confined to this organelle, thus providing the biochemical and
      molecular bases of the peroxisome biogenesis disorders (PBD).
    explanation: >-
      This review directly supports PEX-gene-mediated peroxisome assembly
      failure as the molecular basis of ZSD.
  - reference: PMID:27941306
    reference_title: Peroxisome biogenesis and human peroxisome-deficiency disorders.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Peroxisome is a single-membrane-bounded ubiquitous organelle containing
      a hundred different enzymes that catalyze various metabolic pathways
    explanation: >-
      Fujiki's CHO cell-mutant complementation review supports the role of
      peroxisomes as multifunctional metabolic organelles whose biogenesis
      failure underlies ZSD.
  downstream:
  - target: VLCFA and Branched-Chain Fatty Acid Accumulation
    description: >-
      Without functional peroxisomes, peroxisomal beta- and alpha-oxidation
      pathways fail, allowing VLCFA, phytanic acid, and pristanic acid to
      accumulate in plasma and tissues.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:3119940
      reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        the absence of peroxisomes results in an impairment of metabolic
        processes in which peroxisomes are normally involved
      explanation: >-
        The diagnostic review links absent peroxisomes to impaired peroxisomal
        fatty-acid catabolism upstream of VLCFA and branched-chain fatty-acid
        accumulation.
  - target: Plasmalogen and Bile Acid Intermediate Imbalance
    description: >-
      Loss of peroxisomal ether-lipid synthesis depletes plasmalogens, while
      blocked bile acid side-chain shortening leads to accumulation of
      C27 bile acid intermediates (DHCA, THCA).
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:3119940
      reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These include the catabolism of very long chain (greater than C22) fatty
        acids, the biosynthesis of ether-phospholipids and of bile acids, the
        catabolism of phytanic acid and the catabolism of pipecolic acid.
      explanation: >-
        The review ties absent peroxisomes to impaired ether-phospholipid and
        bile-acid metabolism, the upstream basis for plasmalogen depletion and
        C27 bile-acid intermediate accumulation.
- name: VLCFA and Branched-Chain Fatty Acid Accumulation
  description: >-
    Defective peroxisomal beta-oxidation causes pathologic elevations of
    saturated very long-chain fatty acids (C26:0) and the branched-chain
    fatty acids phytanic and pristanic acid in plasma, fibroblasts, and
    tissues, providing the principal biochemical diagnostic signature.
  biological_processes:
  - preferred_term: very long-chain fatty acid metabolic process
    term:
      id: GO:0000038
      label: very long-chain fatty acid metabolic process
    modifier: DECREASED
  - preferred_term: fatty acid beta-oxidation
    term:
      id: GO:0006635
      label: fatty acid beta-oxidation
    modifier: DECREASED
  - preferred_term: fatty acid alpha-oxidation
    term:
      id: GO:0001561
      label: fatty acid alpha-oxidation
    modifier: DECREASED
  chemical_entities:
  - preferred_term: very-long-chain fatty acids
    term:
      id: CHEBI:27283
      label: very long-chain fatty acid
    modifier: INCREASED
  - preferred_term: branched-chain fatty acids
    term:
      id: CHEBI:35819
      label: branched-chain fatty acid
    modifier: INCREASED
  - preferred_term: phytanic acid
    term:
      id: CHEBI:16285
      label: phytanic acid
    modifier: INCREASED
  - preferred_term: pristanic acid
    term:
      id: CHEBI:51340
      label: pristanic acid
    modifier: INCREASED
  evidence:
  - reference: PMID:29282281
    reference_title: Unbalanced lipolysis results in lipotoxicity and mitochondrial damage in peroxisome-deficient Pex19 mutants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We generated Pex19 Drosophila mutants, which recapitulate the hallmarks
      of PBDs, like absence of peroxisomes, reduced viability,
      neurodegeneration, mitochondrial abnormalities, and accumulation of
      VLCFAs.
    explanation: >-
      Drosophila Pex19 model recapitulates VLCFA accumulation, the defining
      biochemical signature of ZSD.
  - reference: PMID:36649687
    reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PDs are characterized by abnormal elevations of very-long-chain fatty
      acids (VLCFA).
    explanation: >-
      Clinical case series confirms VLCFA elevation as the defining
      biochemical feature of peroxisomal disorders including ZSD.
  downstream:
  - target: Multi-System Clinical Phenotype
    description: >-
      Accumulated lipid species and absent peroxisomal products contribute to
      neuronal migration defects, demyelination, hepatic dysfunction, renal
      cysts, and craniofacial abnormalities.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - lipotoxicity and mitochondrial damage
    - neurodegeneration
    evidence:
    - reference: PMID:29282281
      reference_title: Unbalanced lipolysis results in lipotoxicity and mitochondrial damage in peroxisome-deficient Pex19 mutants.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We generated Pex19 Drosophila mutants, which recapitulate the hallmarks
        of PBDs, like absence of peroxisomes, reduced viability,
        neurodegeneration, mitochondrial abnormalities, and accumulation of
        VLCFAs.
      explanation: >-
        The peroxisome-deficient model links VLCFA accumulation with
        neurodegeneration and mitochondrial abnormalities, supporting an
        indirect route from lipid accumulation to the clinical phenotype.
  - target: Very-long-chain fatty acids
    description: >-
      Impaired peroxisomal beta-oxidation is measured clinically as elevated
      plasma very-long-chain fatty acids.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36649687
      reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        PDs are characterized by abnormal elevations of very-long-chain fatty
        acids (VLCFA).
      explanation: >-
        The clinical series supports elevated VLCFA as a direct biochemical
        readout of peroxisomal fatty-acid oxidation failure.
  - target: Phytanic acid
    description: >-
      Impaired peroxisomal alpha-oxidation can elevate plasma phytanic acid.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:3119940
      reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        plasma phytanic acid concentrations may be elevated.
      explanation: >-
        The diagnostic review supports phytanic acid elevation as a biochemical
        readout of the branched-chain fatty-acid catabolism defect.
- name: Plasmalogen and Bile Acid Intermediate Imbalance
  description: >-
    Loss of peroxisomal ether-phospholipid synthesis depletes red blood cell
    and tissue plasmalogens, while blocked bile acid side-chain shortening
    produces accumulation of dihydroxycholestanoic acid (DHCA) and
    trihydroxycholestanoic acid (THCA). Plasmalogen deficiency is implicated
    in CNS myelin instability.
  biological_processes:
  - preferred_term: ether lipid biosynthetic process
    term:
      id: GO:0008611
      label: ether lipid biosynthetic process
    modifier: DECREASED
  - preferred_term: bile acid metabolic process
    term:
      id: GO:0008206
      label: bile acid metabolic process
    modifier: DECREASED
  chemical_entities:
  - preferred_term: plasmalogens
    term:
      id: CHEBI:64611
      label: ether lipid
    modifier: DECREASED
  - preferred_term: C27 bile acid intermediates
    term:
      id: CHEBI:3098
      label: bile acid
    modifier: INCREASED
  evidence:
  - reference: PMID:34628380
    reference_title: "IMPAIRMENT OF PEROXISOME BIOGENESIS IN THE SPECTRUM OF ZELLWEGER SYNDROME (CLINICAL CASE)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      it is worth investigating the level of long-chain fatty acids,
      plasmalogen of erythrocytes, intermediate metabolites of bile acid
      synthesis, or carrying out genetic sequencing.
    explanation: >-
      Clinical case report supports erythrocyte plasmalogen depletion and
      bile acid intermediate accumulation as biochemical hallmarks of ZSD.
  downstream:
  - target: Multi-System Clinical Phenotype
    description: >-
      Plasmalogen deficiency contributes to dysmyelination and neurologic
      dysfunction; accumulated bile acid intermediates contribute to
      cholestatic liver disease.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - plasmalogen deficiency
    - bile acid intermediate accumulation
    evidence:
    - reference: PMID:36914043
      reference_title: Quantitative analysis of ethanolamine plasmalogen species in red blood cells using liquid chromatography tandem mass spectrometry for diagnosing peroxisome biogenesis disorders.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Markedly reduced plasmalogens are a classic feature of peroxisome
        biogenesis disorders (PBD) because plasmalogen synthesis requires
        functional peroxisomes.
      explanation: >-
        The clinical laboratory study links peroxisome biogenesis disorders to
        plasmalogen deficiency, a known contributor to neurologic dysfunction.
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        progressive peroxisome dysfunction variably manifest as sensory loss
        (secondary to retinal dystrophy and sensorineural hearing loss),
        neurologic involvement (ataxia, polyneuropathy, and leukodystrophy),
        liver dysfunction, adrenal insufficiency, and renal oxalate stones.
      explanation: >-
        GeneReviews supports progressive peroxisome dysfunction as the clinical
        context for neurologic, sensory, hepatic, adrenal, and renal disease.
  - target: Plasmalogens
    description: >-
      Impaired peroxisomal ether-lipid biosynthesis lowers erythrocyte and
      tissue plasmalogens.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36914043
      reference_title: Quantitative analysis of ethanolamine plasmalogen species in red blood cells using liquid chromatography tandem mass spectrometry for diagnosing peroxisome biogenesis disorders.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Markedly reduced plasmalogens are a classic feature of peroxisome
        biogenesis disorders (PBD) because plasmalogen synthesis requires
        functional peroxisomes.
      explanation: >-
        This directly supports reduced plasmalogens as a readout of impaired
        peroxisome-dependent ether-lipid synthesis.
  - target: C27 bile acid intermediates (DHCA, THCA)
    description: >-
      Blocked peroxisomal bile-acid side-chain shortening leads to accumulation
      of abnormal C27 bile-acid intermediates.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:3119940
      reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        In classic Zellweger syndrome abnormal C27-bile acids, very long chain
        fatty acids, dicarboxylic acids and pipecolic acid accumulate in the
        plasma of the patients.
      explanation: >-
        The diagnostic review supports C27 bile-acid accumulation as a direct
        readout of peroxisomal bile-acid metabolism failure.
- name: Multi-System Clinical Phenotype
  description: >-
    Combined toxic accumulation and product deficiency produce the
    characteristic Zellweger phenotype: profound hypotonia, intractable
    seizures, craniofacial dysmorphism, leukodystrophy, hepatic dysfunction,
    renal cortical cysts, and progressive sensory loss.
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected newborns are hypotonic and feed poorly.
    explanation: >-
      GeneReviews directly supports the early multi-system clinical
      presentation of severe ZSD.
  - reference: PMID:15868469
    reference_title: "Peroxisome biogenesis disorders: the role of peroxisomes and metabolic dysfunction in developing brain."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Peroxisome biogenesis disorders, of which Zellweger syndrome is the
      most severe, result in severe neurological dysfunction associated with
      abnormal CNS neuronal migrations due to the lack of functional
      peroxisomes.
    explanation: >-
      PEX2 mouse model supports neuronal migration defects as a core
      neurodevelopmental consequence of peroxisome deficiency.
  downstream:
  - target: Neonatal Hypotonia
    description: >-
      The severe neonatal ZSD presentation includes hypotonia as an early
      neuromuscular manifestation of peroxisome biogenesis failure.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Affected newborns are hypotonic and feed poorly.
      explanation: GeneReviews directly links severe neonatal ZSD with hypotonia.
  - target: Feeding Difficulties
    description: >-
      Severe neonatal ZSD often causes poor feeding, linking the multisystem
      neonatal phenotype to nutritional compromise.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Affected newborns are hypotonic and feed poorly.
      explanation: GeneReviews directly lists poor feeding in affected newborns.
  - target: Seizures
    description: >-
      Congenital neuronal migration defects in severe ZSD produce
      neonatal-onset seizures.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        neuronal migration defects associated with neonatal-onset seizures
      explanation: GeneReviews links neuronal migration defects with neonatal seizures.
  - target: Characteristic Craniofacial Features
    description: >-
      Severe ZSD includes distinctive craniofacial dysmorphism as part of the
      congenital malformation spectrum.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        They have distinctive facies
      explanation: GeneReviews directly supports distinctive facies in severe ZSD.
  - target: Hepatomegaly
    description: >-
      Peroxisomal bile-acid and lipid metabolism failure manifests clinically
      as liver involvement, including hepatomegaly, in severe and milder ZSD.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        liver disease that can be severe
      explanation: GeneReviews supports severe liver disease as part of ZSD.
  - target: Renal Cysts
    description: >-
      Severe ZSD includes renal cysts among the congenital malformations
      associated with peroxisome biogenesis failure.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        neuronal migration defects associated with neonatal-onset seizures,
        renal cysts, and bony stippling
      explanation: GeneReviews lists renal cysts among severe ZSD malformations.
  - target: Chondrodysplasia Punctata
    description: >-
      Severe ZSD includes bony stippling of the patellae and long bones,
      captured clinically as chondrodysplasia punctata.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        renal cysts, and bony stippling
      explanation: GeneReviews lists bony stippling as part of severe ZSD.
  - target: Sensorineural Hearing Loss
    description: >-
      Progressive peroxisome dysfunction causes sensory loss that includes
      sensorineural hearing impairment.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        sensory loss (secondary to retinal dystrophy and sensorineural hearing
        loss)
      explanation: GeneReviews links ZSD sensory loss to sensorineural hearing loss.
  - target: Retinitis Pigmentosa
    description: >-
      Progressive peroxisome dysfunction causes retinal dystrophy, represented
      in the pathograph as retinal degeneration/retinitis pigmentosa.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        sensory loss (secondary to retinal dystrophy and sensorineural hearing
        loss)
      explanation: GeneReviews links progressive sensory loss to retinal dystrophy.
  - target: Leukodystrophy
    description: >-
      Progressive peroxisome dysfunction causes neurologic involvement that
      includes leukodystrophy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
      explanation: GeneReviews directly lists leukodystrophy in milder ZSD.
  - target: Ataxia
    description: >-
      Progressive neurologic involvement in intermediate/milder ZSD includes
      ataxia.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
      explanation: GeneReviews directly lists ataxia in milder ZSD.
  - target: Polyneuropathy
    description: >-
      Progressive neurologic involvement in intermediate/milder ZSD includes
      polyneuropathy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
      explanation: GeneReviews directly lists polyneuropathy in milder ZSD.
  - target: Developmental Delay
    description: >-
      The neurologic impact of ZSD commonly includes developmental delay,
      although intellect can be normal at the mildest end.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        While hypotonia and developmental delays are typical, intellect can be
        normal.
      explanation: GeneReviews supports developmental delay across the ZSD spectrum.
  - target: Adrenal Insufficiency
    description: >-
      Progressive peroxisome dysfunction includes adrenal insufficiency,
      particularly in milder ZSD presentations.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        liver dysfunction, adrenal insufficiency, and renal oxalate stones.
      explanation: GeneReviews lists adrenal insufficiency among ZSD manifestations.
  - target: Nephrolithiasis
    description: >-
      Progressive peroxisome dysfunction can include renal oxalate stones.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        liver dysfunction, adrenal insufficiency, and renal oxalate stones.
      explanation: GeneReviews lists renal oxalate stones in intermediate/milder ZSD.
  - target: Osteopenia
    description: >-
      Some individuals with ZSD have reduced bone mineral density.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Some have osteopenia; almost all have ameleogenesis imperfecta in the
        secondary teeth.
      explanation: GeneReviews supports osteopenia in a subset of individuals.
  - target: Amelogenesis Imperfecta
    description: >-
      Dental enamel involvement in secondary teeth is a common ZSD
      manifestation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Some have osteopenia; almost all have ameleogenesis imperfecta in the
        secondary teeth.
      explanation: GeneReviews supports amelogenesis imperfecta in secondary teeth.
phenotypes:
- name: Neonatal Hypotonia
  category: Neurologic
  diagnostic: true
  description: >-
    Profound generalized hypotonia is one of the earliest and most consistent
    presenting features of severe Zellweger spectrum disorders.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Affected newborns are hypotonic and feed poorly.
    explanation: >-
      GeneReviews directly supports neonatal hypotonia as a defining
      presenting feature of ZSD.
- name: Feeding Difficulties
  category: Gastrointestinal
  description: >-
    Poor feeding is an early neonatal manifestation that often contributes to
    nutritional compromise and the need for supportive feeding care.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected newborns are hypotonic and feed poorly.
    explanation: >-
      GeneReviews directly supports poor feeding in affected newborns.
- name: Seizures
  category: Neurologic
  description: >-
    Neonatal-onset seizures, often intractable, are characteristic of
    classic Zellweger syndrome.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      neuronal migration defects associated with neonatal-onset seizures
    explanation: >-
      GeneReviews supports neonatal-onset seizures as a characteristic
      congenital malformation phenotype of severe ZSD.
- name: Hepatomegaly
  category: Hepatic
  description: >-
    Hepatomegaly is a specific hepatic manifestation within the severe liver
    disease seen in Zellweger spectrum disorders.
  phenotype_term:
    preferred_term: Hepatomegaly
    term:
      id: HP:0002240
      label: Hepatomegaly
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      liver disease that can be severe
    explanation: >-
      GeneReviews supports hepatic disease as a major organ-system phenotype
      of severe ZSD.
- name: Sensorineural Hearing Loss
  category: Auditory
  description: >-
    Progressive sensorineural hearing loss is a frequent feature, particularly
    in the milder NALD and IRD forms.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      sensory loss (secondary to retinal dystrophy and sensorineural hearing
      loss)
    explanation: >-
      GeneReviews supports sensorineural hearing loss as a recognized
      progressive sensory phenotype of milder ZSD.
- name: Retinitis Pigmentosa
  category: Ophthalmologic
  description: >-
    Progressive retinal degeneration with retinitis pigmentosa is a hallmark
    of the milder NALD and IRD phenotypes.
  phenotype_term:
    preferred_term: Retinal degeneration
    term:
      id: HP:0000546
      label: Retinal degeneration
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      sensory loss (secondary to retinal dystrophy and sensorineural hearing
      loss)
    explanation: >-
      GeneReviews supports retinal dystrophy as a key sensory phenotype in
      milder ZSD.
- name: Cataract
  category: Ophthalmologic
  frequency: OCCASIONAL
  description: >-
    Cataracts, which may be congenital in the severe neonatal form, are a
    recognized ophthalmologic manifestation of ZSD distinct from the
    progressive retinal dystrophy, and are frequent enough that cataract
    removal is part of standard supportive management.
  phenotype_term:
    preferred_term: Cataract
    term:
      id: HP:0000518
      label: Cataract
  evidence:
  - reference: PMID:33335840
    reference_title: "Zellweger spectrum disorder: A cross-sectional study of symptom prevalence using input from family caregivers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cataracts were reported by 18% and 14% of caregivers of living and
      deceased individuals, respectively.
    explanation: >-
      Caregiver-reported cross-sectional study documents cataracts as a
      recurrent ophthalmologic feature across the ZSD spectrum.
- name: Characteristic Craniofacial Features
  category: Craniofacial
  description: >-
    Craniofacial features including high forehead, large fontanelles, flat
    occiput, and broad nasal bridge are characteristic of classic Zellweger
    syndrome.
  phenotype_term:
    preferred_term: Abnormal facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      They have distinctive facies
    explanation: >-
      GeneReviews supports distinctive facial features as a hallmark of
      severe ZSD.
- name: Adrenal Insufficiency
  category: Endocrine
  description: >-
    Primary adrenal insufficiency is common in ZSD, frequently asymptomatic
    in milder forms, and associated with specific PEX1 variants.
  phenotype_term:
    preferred_term: Adrenal insufficiency
    term:
      id: HP:0000846
      label: Adrenal insufficiency
  evidence:
  - reference: PMID:25179809
    reference_title: High prevalence of primary adrenal insufficiency in Zellweger spectrum disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Primary adrenal insufficiency was found in 7/24 patients examined,
      with 4/7 being asymptomatic.
    explanation: >-
      Clinical cohort study supports adrenal insufficiency as a frequent
      and often asymptomatic phenotype in ZSD.
- name: Renal Cysts
  category: Renal
  description: >-
    Renal cortical cysts are a near-universal congenital malformation of severe
    Zellweger syndrome.
  phenotype_term:
    preferred_term: Renal cyst
    term:
      id: HP:0000107
      label: Renal cyst
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      neuronal migration defects associated with neonatal-onset seizures,
      renal cysts, and bony stippling
    explanation: >-
      GeneReviews supports renal cortical cysts as a characteristic congenital
      malformation of severe ZSD.
- name: Chondrodysplasia Punctata
  category: Skeletal
  description: >-
    Punctate epiphyseal calcifications (chondrodysplasia punctata) of the
    patellae and long bones are a characteristic congenital skeletal feature
    of severe Zellweger syndrome.
  phenotype_term:
    preferred_term: Chondrodysplasia punctata
    term:
      id: HP:0010655
      label: Epiphyseal stippling
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      renal cysts, and bony stippling
    explanation: >-
      GeneReviews supports chondrodysplasia punctata (epiphyseal stippling) as
      a characteristic congenital skeletal malformation of severe ZSD.
- name: Leukodystrophy
  category: Neurologic
  description: >-
    Progressive white matter disease (leukodystrophy) is a major neurologic
    feature of the intermediate (NALD) and milder (IRD) ZSD phenotypes.
  phenotype_term:
    preferred_term: Leukodystrophy
    term:
      id: HP:0002415
      label: Leukodystrophy
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
    explanation: >-
      GeneReviews supports leukodystrophy as a major progressive neurologic
      phenotype of milder ZSD.
- name: Developmental Delay
  category: Neurodevelopmental
  description: >-
    Global developmental delay is a typical feature across the Zellweger
    spectrum, although intellect can be normal in the mildest cases.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      While hypotonia and developmental delays are typical, intellect can be
      normal.
    explanation: >-
      GeneReviews supports developmental delay as a typical neurodevelopmental
      phenotype across the ZSD spectrum.
- name: Ataxia
  category: Neurologic
  description: >-
    Ataxia occurs in intermediate and milder ZSD as part of progressive
    neurologic involvement.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
    explanation: GeneReviews directly lists ataxia in intermediate/milder ZSD.
- name: Polyneuropathy
  category: Neurologic
  description: >-
    Polyneuropathy occurs in intermediate and milder ZSD as part of progressive
    neurologic involvement.
  phenotype_term:
    preferred_term: Polyneuropathy
    term:
      id: HP:0001271
      label: Polyneuropathy
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      neurologic involvement (ataxia, polyneuropathy, and leukodystrophy)
    explanation: GeneReviews directly lists polyneuropathy in intermediate/milder ZSD.
- name: Nephrolithiasis
  category: Renal
  description: >-
    Renal oxalate stones occur in intermediate and milder ZSD and require
    renal surveillance and supportive management.
  phenotype_term:
    preferred_term: Renal oxalate stones
    term:
      id: HP:0000787
      label: Nephrolithiasis
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      liver dysfunction, adrenal insufficiency, and renal oxalate stones.
    explanation: GeneReviews directly lists renal oxalate stones in ZSD.
- name: Osteopenia
  category: Skeletal
  description: >-
    Reduced bone mineral density is reported in a subset of individuals with
    ZSD.
  phenotype_term:
    preferred_term: Osteopenia
    term:
      id: HP:0000938
      label: Osteopenia
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Some have osteopenia; almost all have ameleogenesis imperfecta in the
      secondary teeth.
    explanation: GeneReviews supports osteopenia in some individuals with ZSD.
- name: Amelogenesis Imperfecta
  category: Dental
  description: >-
    Dental enamel dysplasia of the secondary teeth is a common manifestation in
    ZSD survivors.
  phenotype_term:
    preferred_term: Amelogenesis imperfecta
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Some have osteopenia; almost all have ameleogenesis imperfecta in the
      secondary teeth.
    explanation: GeneReviews supports amelogenesis imperfecta of secondary teeth.
biochemical:
- name: Very-long-chain fatty acids
  presence: Increased
  context: >-
    Elevated plasma VLCFA (C26:0) is the principal biochemical screening test
    for Zellweger spectrum disorders.
  readouts:
  - target: VLCFA and Branched-Chain Fatty Acid Accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Increased plasma VLCFA directly reports the peroxisomal VLCFA
      beta-oxidation block.
  biomarker_term:
    preferred_term: very long-chain fatty acid
    term:
      id: CHEBI:27283
      label: very long-chain fatty acid
  evidence:
  - reference: PMID:36649687
    reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PDs are characterized by abnormal elevations of very-long-chain fatty
      acids (VLCFA).
    explanation: >-
      Supports VLCFA elevation as the defining biochemical abnormality
      across peroxisomal disorders including ZSD.
- name: Phytanic acid
  presence: Increased
  context: >-
    Phytanic acid accumulates due to impaired peroxisomal alpha-oxidation.
  readouts:
  - target: VLCFA and Branched-Chain Fatty Acid Accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Elevated phytanic acid reports impaired peroxisomal branched-chain fatty
      acid catabolism within the same lipid-metabolism failure branch.
  biomarker_term:
    preferred_term: phytanic acid
    term:
      id: CHEBI:16285
      label: phytanic acid
  evidence:
  - reference: PMID:3119940
    reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      plasma phytanic acid concentrations may be elevated.
    explanation: >-
      Biochemical diagnostic review supports elevated phytanic acid as a
      Zellweger biochemical abnormality.
- name: Plasmalogens
  presence: Decreased
  context: >-
    Erythrocyte plasmalogens are reduced because peroxisomal ether-lipid
    synthesis is impaired.
  readouts:
  - target: Plasmalogen and Bile Acid Intermediate Imbalance
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Decreased red blood cell plasmalogens report failure of peroxisomal
      ether-lipid synthesis.
  biomarker_term:
    preferred_term: plasmalogens
    term:
      id: CHEBI:64611
      label: ether lipid
  evidence:
  - reference: PMID:36914043
    reference_title: Quantitative analysis of ethanolamine plasmalogen species in red blood cells using liquid chromatography tandem mass spectrometry for diagnosing peroxisome biogenesis disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Markedly reduced plasmalogens are a classic feature of peroxisome
      biogenesis disorders (PBD) because plasmalogen synthesis requires
      functional peroxisomes.
    explanation: >-
      Clinical laboratory study supports reduced plasmalogens as a classic
      biochemical feature of peroxisome biogenesis disorders.
- name: C27 bile acid intermediates (DHCA, THCA)
  presence: Increased
  context: >-
    Dihydroxycholestanoic and trihydroxycholestanoic acids accumulate because
    peroxisomal side-chain shortening of cholesterol-derived bile acid
    precursors is blocked.
  readouts:
  - target: Plasmalogen and Bile Acid Intermediate Imbalance
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Increased C27 bile acid intermediates report impaired peroxisomal bile
      acid side-chain shortening.
  biomarker_term:
    preferred_term: C27 bile acid intermediates
    term:
      id: CHEBI:3098
      label: bile acid
  evidence:
  - reference: PMID:3119940
    reference_title: "Zellweger syndrome: biochemical procedures in diagnosis, prevention and treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      abnormal C27-bile acids, very long chain fatty acids, dicarboxylic
      acids and pipecolic acid accumulate in the plasma of the patients.
    explanation: >-
      Biochemical diagnostic review supports C27 bile acid accumulation as a
      plasma abnormality in classic Zellweger syndrome.
genetic:
- name: PEX1
  gene_term:
    preferred_term: PEX1
    term:
      id: hgnc:8850
      label: PEX1
  association: >-
    Autosomal recessive causal pathogenic variant; PEX1 is the most common
    cause of ZSD. Specific PEX1 variants in exon 13 are associated with
    primary adrenal insufficiency.
  evidence:
  - reference: PMID:36649687
    reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      all the 3 patients with PBD and adrenal insufficiency who were on
      steroid supplementation had the compound heterozygous pathogenic
      variant in exon 13 of PEX1
    explanation: >-
      Clinical case series supports a specific PEX1 compound-heterozygous
      genotype as causal for ZSD with adrenal insufficiency.
- name: PEX6
  gene_term:
    preferred_term: PEX6
    term:
      id: hgnc:8859
      label: PEX6
  association: >-
    Autosomal recessive causal pathogenic variant; PEX6 variants are a
    recognized cause of Zellweger syndrome, often associated with severe
    phenotypes when leading to truncation.
  evidence:
  - reference: PMID:10408779
    reference_title: Genomic structure and identification of 11 novel mutations of the PEX6 (peroxisome assembly factor-2) gene in patients with peroxisome biogenesis disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most of the mutations led to premature termination or large deletions
      of the PEX6 protein and resulted in the most severe peroxisome
      biogenesis disorder phenotype of Zellweger syndrome.
    explanation: >-
      Direct sequencing study supports PEX6 truncating mutations as causal
      for the most severe Zellweger phenotype.
- name: PEX12
  gene_term:
    preferred_term: PEX12
    term:
      id: hgnc:8854
      label: PEX12
  association: Autosomal recessive causal pathogenic variant in the ZSD spectrum.
  evidence:
  - reference: PMID:17055079
    reference_title: Peroxisome biogenesis disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      DNA testing is possible for all of the disorders, but is more
      challenging for the ZSS since 12 PEX genes are known to be associated
      with this spectrum of PBD.
    explanation: >-
      Steinberg review supports the multi-gene PEX-based architecture of the
      ZSD/ZSS spectrum, in which PEX12 is one of the recognized causal genes.
diagnosis:
- name: Plasma very-long-chain fatty acid measurement
  description: >-
    Plasma VLCFA testing is the first-line biochemical screen for Zellweger
    spectrum disorders and remains the cornerstone of ZSD diagnosis.
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  evidence:
  - reference: PMID:36649687
    reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PDs are characterized by abnormal elevations of very-long-chain fatty
      acids (VLCFA).
    explanation: >-
      Clinical case series supports VLCFA measurement as the defining
      biochemical diagnostic test in peroxisomal disorders.
- name: C26:0-lysophosphatidylcholine in dried blood spots
  description: >-
    Measurement of C26:0-lysophosphatidylcholine (C26:0-lysoPC) in dried blood
    spots is a sensitive VLCFA-based marker for ZSD, adopted in the diagnostic
    work-up and usable for newborn screening (including incidental detection
    within X-linked adrenoleukodystrophy newborn-screening programs).
  diagnosis_term:
    preferred_term: Laboratory Procedure
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  evidence:
  - reference: PMID:28677031
    reference_title: "Evaluation of C26:0-lysophosphatidylcholine and C26:0-carnitine as diagnostic markers for Zellweger spectrum disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      C26:0-lysoPC in DBS is a sensitive and useful marker for VLCFA
      accumulation in patients with a ZSD.
    explanation: >-
      Case-control biomarker study supports dried-blood-spot C26:0-lysoPC as a
      sensitive diagnostic marker for ZSD, with newborn-screening potential.
  - reference: PMID:28677031
    reference_title: "Evaluation of C26:0-lysophosphatidylcholine and C26:0-carnitine as diagnostic markers for Zellweger spectrum disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This marker has the potential to be used for newborn screening for ZSD.
    explanation: >-
      Supports the newborn-screening applicability of dried-blood-spot
      C26:0-lysoPC for ZSD detection.
- name: Molecular genetic testing of PEX genes
  description: >-
    Identification of biallelic pathogenic variants in one of the 13 known
    ZSD-PEX genes establishes the molecular diagnosis.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of ZSD is established in a proband with the suggestive
      clinical and biochemical findings above by identification of biallelic
      pathogenic variants in one of the 13 known ZSD-PEX genes.
    explanation: >-
      GeneReviews directly supports biallelic PEX gene testing as the
      molecular diagnostic standard for ZSD.
treatments:
- name: Supportive Care
  description: >-
    There is no curative therapy for Zellweger spectrum disorders. Care is
    multidisciplinary and supportive, addressing seizures, feeding,
    hepatic dysfunction, hearing, and vision.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  - preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  - preferred_term: Retinal degeneration
    term:
      id: HP:0000546
      label: Retinal degeneration
  - preferred_term: Cataract
    term:
      id: HP:0000518
      label: Cataract
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The focus is on symptomatic therapy and may include gastrostomy to
      provide adequate calories, hearing aids, cataract removal, glasses to
      correct refractive errors, supplementation of fat-soluble vitamins,
      and cholic acid supplementation
    explanation: >-
      GeneReviews supports symptomatic/supportive management as the standard
      of care across the ZSD spectrum.
- name: Adrenal Replacement Therapy
  description: >-
    Patients with documented primary adrenal insufficiency with ZSD receive
    glucocorticoid (and sometimes mineralocorticoid) replacement.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: hydrocortisone
      term:
        id: CHEBI:17650
        label: cortisol
  target_phenotypes:
  - preferred_term: Adrenal insufficiency
    term:
      id: HP:0000846
      label: Adrenal insufficiency
  evidence:
  - reference: PMID:25179809
    reference_title: High prevalence of primary adrenal insufficiency in Zellweger spectrum disorders.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is important to detect impaired adrenal function because it has
      treatment implications.
    explanation: >-
      Clinical cohort study supports systematic adrenal-function screening
      and replacement therapy as a treatment-relevant intervention in ZSD.
  - reference: PMID:36649687
    reference_title: "Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Three patients were on daily hydrocortisone replacement, and 1 patient
      was on stress-dose hydrocortisone only as needed.
    explanation: >-
      Peroxisomal-disorder case series directly documents hydrocortisone
      replacement in patients with adrenal insufficiency.
- name: Cholic Acid Supplementation
  description: >-
    Oral cholic acid supplementation is used as part of symptomatic management
    for ZSD, where peroxisomal bile acid synthesis is disrupted and C27 bile
    acid intermediates accumulate.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: cholic acid
      term:
        id: CHEBI:16359
        label: cholic acid
  target_mechanisms:
  - target: Plasmalogen and Bile Acid Intermediate Imbalance
    treatment_effect: MODULATES
    description: >-
      Cholic acid supplementation is linked to the bile-acid-intermediate branch
      of peroxisomal metabolic dysfunction.
    evidence:
    - reference: PMID:20301621
      reference_title: Zellweger Spectrum Disorder.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        supplementation of fat-soluble vitamins, and cholic acid supplementation
      explanation: GeneReviews lists cholic acid supplementation in ZSD management.
  evidence:
  - reference: PMID:20301621
    reference_title: Zellweger Spectrum Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      supplementation of fat-soluble vitamins, and cholic acid supplementation
    explanation: >-
      GeneReviews directly supports cholic acid supplementation as a
      treatment used in the symptomatic management of ZSD.
datasets: []
references:
- reference: PMID:20301621
  title: Zellweger Spectrum Disorder.
  tags:
  - GeneReviews
  findings: []

📚

References & Deep Research

References

1

PMID:20301621

Zellweger Spectrum Disorder.

No top-level findings curated for this source.

Deep Research

1

Claude Code ▸

Zellweger Spectrum Disorder (ZSD): Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 48 citations 2026-07-26T13:28:46.554241

Zellweger Spectrum Disorder (ZSD): Comprehensive Research Report

1. Disease Information

Overview. Zellweger spectrum disorder (ZSD) is the most common and clinically most severe subgroup of the peroxisome biogenesis disorders (PBDs), a group of autosomal recessive conditions caused by failure to assemble functional peroxisomes. ZSD represents a single biochemical and clinical continuum — historically split into three "distinct" diagnoses (Zellweger syndrome [most severe], neonatal adrenoleukodystrophy [NALD, intermediate], and infantile Refsum disease [IRD, mildest]) that are now recognized as points along one spectrum defined by residual peroxin function (GeneReviews, NBK1448; Klouwer et al. 2015, PMID:26627182). As the GeneReviews summary states, "Zellweger spectrum disorder... spans a phenotypic continuum ranging from a severe neonatal-onset form... to a milder, later-onset form."

Key identifiers: - MONDO: MONDO:0013932 (Zellweger syndrome; related MONDO IDs exist per causal gene, e.g., PBD1A, PBD1B) - OMIM (phenotype series/individual entries — see §4 below for the full gene-keyed list): PS214100 (Peroxisome biogenesis disorder, Zellweger syndrome spectrum) - Orphanet: ORPHA:912 (Zellweger syndrome), ORPHA:79189 (Peroxisome biogenesis disorder), with related entries for NALD (ORPHA:44) and IRD - ICD-10-CM: E71.518 (Other disorders of peroxisome biogenesis); Zellweger syndrome is also sometimes captured under Q87.8 (other specified congenital malformation syndromes) - ICD-11: 5C57.0 - MeSH: D015211 (Zellweger Syndrome); C536664 (Peroxisome biogenesis disorders)

Synonyms: Zellweger syndrome; cerebrohepatorenal syndrome; peroxisome biogenesis disorder–Zellweger syndrome spectrum (PBD-ZSS); neonatal adrenoleukodystrophy (NALD); infantile Refsum disease (IRD); peroxisomal 3-oxoacyl-CoA thiolase deficiency (historically confused with, but distinct from, ZSD).

Evidence basis of curated information: The literature is a mixture of aggregated disease-level resources (GeneReviews, Orphanet, OMIM, NORD) and primary clinical cohort/registry studies (natural history studies, caregiver surveys, medical chart reviews) — i.e., largely aggregated, disease-level characterizations supplemented by individual-patient cohort data (e.g., the NIH/Kennedy Krinstitute Longitudinal Natural History Study, NCT01668186; the caregiver cross-sectional study, PMID:33335840).

2. Etiology

Disease causal factors — genetic, monogenic. ZSD is caused exclusively by biallelic pathogenic variants in one of 13 known PEX genes, which encode "peroxins" required for peroxisomal membrane biogenesis and/or peroxisomal matrix protein import. There is no known environmental, infectious, or purely mechanistic (non-genetic) cause.

Genetic risk factors (causal genes, ranked by mutation frequency in ZSD cohorts, per GeneReviews):

Gene	HGNC symbol	Approx. % of ZSD cases	OMIM gene	Function
PEX1	PEX1	60.5%	*602136	AAA-ATPase, PEX5/PEX7 receptor recycling (with PEX6)
PEX6	PEX6	14.5%	*601498	AAA-ATPase, partner of PEX1
PEX12	PEX12	7.6%	RING-finger peroxin, matrix import
PEX26	PEX26	4.2%	Membrane peroxin, recruits PEX1/PEX6 to peroxisome
PEX10	PEX10	3.4%	RING-finger peroxin, matrix import
PEX2	PEX2	3.1%	RING-finger peroxin, matrix import
PEX5	PEX5	2.0%	PTS1 receptor
PEX13	PEX13	1.5%	Docking-complex peroxin
PEX16	PEX16	1.1%	Membrane biogenesis peroxin
PEX3, PEX19, PEX14, PEX11B	—	<1% each	Membrane biogenesis (PEX3/19/16), division (PEX11B), docking (PEX14)

Source: GeneReviews NBK1448.

Corresponding OMIM phenotype entries include PBD1A/PBD1B (PEX1, #214100/*601539), PBD2A (PEX5, #214110), PBD3A (PEX12, #614859), PBD4A (PEX6, #614862), PBD5A (PEX2, #614866), PBD6A (PEX10, #614870), PBD7A (PEX26, #614872), PBD13A (PEX13, #614887 — approximate), among others (OMIM.org).

Risk variant example — PEX1 p.Gly843Asp (c.2528G>A, rs61750420): This is the single most common ZSD-causing allele in patient cohorts (allele frequency ~0.43 among PEX1-mutant alleles per Steinberg et al. 2006), yet it is rare in the general population (gnomAD/ClinVar general-population allele frequency ≈0.00033, i.e., ~1/3000 chromosomes) (ClinVar RCV000007946). It retains ~15% of wild-type PEX1 activity in patient fibroblasts, explaining its association with the mildest end of the spectrum. Homozygosity for this hypomorphic allele produces a mild phenotype; homozygosity for the null frameshift PEX1 p.Ile700Tyrfs42 (c.2097_2098insT) produces a severe phenotype; compound heterozygosity for the two produces an intermediate* phenotype — a clean genotype–severity correlation (GeneReviews; Mild Zellweger syndrome PEX1 variants, PMC6968987).

Founder effects (population-specific risk): - French-Canadian (Saguenay–Lac-Saint-Jean, Quebec): a PEX6 founder mutation drives an incidence of ~1/12,000 births, one of the highest in the world (PMC3483250). - PEX6 founder variant also reported causing Zellweger syndrome via possible founder effect in Mixteco (Mexican indigenous) neonates (PMC10573658). - Japan's markedly lower incidence (1/500,000) is attributed to the absence of the common European PEX1 founder variants (p.Ile700Tyrfs*42 and p.Gly843Asp). - Saudi Arabia and other high-consanguinity populations report increased ZSD prevalence attributable to consanguineous unions rather than a single founder allele.

Environmental/lifestyle risk factors: None established — ZSD is a fully penetrant monogenic disease; there is no reported gene–environment interaction modulating risk of disease occurrence. (Environmental/nutritional factors, e.g., DHA status, are relevant to secondary disease severity/management, not causation — see §12.)

Protective factors: None known at the genetic-modifier level beyond residual-activity ("hypomorphic") missense alleles, which are protective relative to null alleles in a dose-dependent way but do not prevent disease. No environmental protective exposure has been described.

Gene–environment interactions: Not applicable in the causal sense; however, catabolic stress (intercurrent illness, fasting) can unmask or worsen adrenal insufficiency and hepatic decompensation in patients with residual peroxisomal function, an indirect gene-modulated environmental interaction relevant to clinical management.

3. Phenotypes

ZSD is multisystemic. Below, phenotypes are grouped by type, with suggested HPO terms, and typical onset/severity/frequency data drawn from the largest systematic sources: the Klouwer 2015 review (PMID:26627182), the 2022 scoping review/meta-analysis/medical chart review by Berendse et al., "Characterization of Severity in Zellweger Spectrum Disorder by Clinical Findings" (PMID:35741019), and the caregiver cross-sectional study (Bose et al. 2020, PMID:33335840).

Neurological

Hypotonia (HP:0001252) — near-universal in severe/neonatal presentation; present in ~72% of "intermediate" category patients in the natural-history cohort.
Seizures (HP:0001250) — 100% in severe category (n=23), 41.3% in intermediate (n=63), 16.3% in mild (n=49) — a graded, severity-defining feature.
Abnormal EEG (HP:0002353) — 100% in severe category (n=17 assessed).
Global developmental delay (HP:0001263) — 97.5% in intermediate category (n=40); present in virtually all severe patients; may be absent or mild in the mildest phenotype.
Neuronal migration defects (e.g., polymicrogyria, HP:0002126; pachygyria HP:0001302) — characteristic of the severe/neonatal form, visible on brain MRI.
Progressive leukodystrophy/demyelination (HP:0002352) — reported in a subset, more typical of the "NALD" intermediate presentation, progressive over childhood.
Peripheral neuropathy (HP:0009830) — reported in milder, longer-surviving patients.
Ataxia (HP:0001251) — in milder/longer-surviving phenotypes.

Craniofacial / Dysmorphic

Distinctive facies (HP:0001999) — flat facies, high forehead, large fontanelles, epicanthal folds — most prominent in the severe neonatal form.

Hepatic

Neonatal cholestasis/jaundice (HP:0200034 / HP:0001080).
Hepatomegaly (HP:0002240).
Abnormal liver function (HP:0001410) — 92.9% in intermediate category (n=56).
Vitamin-K-responsive coagulopathy — from fat malabsorption/cholestasis.
Progression to fibrosis, portal hypertension, esophageal varices; hepatocellular carcinoma reported in some surviving adults.

Endocrine

Adrenocortical insufficiency (HP:0000846) — reported by 45% combined prevalence of caregivers (48% living, 40% deceased) in the caregiver survey; 54.2% in the intermediate natural-history category. Often subclinical/evolving and probably underdiagnosed, especially in milder/adult-surviving patients.

Ocular

Progressive retinal dystrophy/retinopathy (HP:0000556 retinal dystrophy; HP:0000512 nystagmus is often an early sign) — "nearly all patients develop a progressive retinopathy leading to blindness"; 89.1% vision loss in intermediate category (n=55).
Cataracts (HP:0000518) — may be congenital, especially severe form.
Glaucoma (HP:0000501).

Auditory

Sensorineural hearing loss (HP:0000407) — described as "almost always present" in childhood-onset patients; a core, near-universal feature across the spectrum, worsening with age.

Skeletal

Chondrodysplasia punctata (stippled epiphyses of patellae and long bones; HP:0002694) — characteristic of the severe neonatal form.
Osteopenia/low bone density (HP:0000939).
Amelogenesis imperfecta (enamel hypoplasia of secondary teeth; HP:0000705).

Renal

Renal cortical cysts (HP:0000107) — 79% in the severe natural-history category (n=19); a common, often congenital finding.
Nephrocalcinosis/urolithiasis from elevated urinary oxalate (HP:0000121 / HP:0000787).

Cardiac

Cardiac structural abnormalities — reported in 81.3% of a small severe-category cohort (n=16) in the meta-analysis (e.g., septal defects); less systematically characterized than other organ systems.

Gastrointestinal/Growth

Feeding difficulties/failure to thrive (HP:0011968/HP:0001508) — 71.9% in intermediate category; 0% (none) in the mild category cohort — a strongly discriminating feature between severity tiers.

Functional/Behavioral (milder end of spectrum)

Independent ambulation achieved in 87.8% of mild-category patients; full-sentence speech in 71.7%.

Phenotype characteristics summary (per severity tier, from the Berendse et al. meta-analysis, PMID:35741019): - Severe: neonatal onset, near-uniform seizures/abnormal EEG, high renal cyst prevalence, mortality before age 2 in 95.7% (n=23). - Intermediate: childhood onset, high rates of developmental delay (97.5%), vision loss (89.1%), abnormal liver function (92.9%), feeding difficulty (71.9%), adrenal insufficiency (54.2%), lower but still substantial seizure rate (41.3%). - Mild: later childhood/adolescent/adult recognition, seizures in only 16.3%, no feeding difficulties, majority ambulatory and verbal, but progressive sensory (vision/hearing) impairment remains prominent even here. - Survival differed significantly across the three severity categories by log-rank test (p<0.001).

Quality-of-life impact: Combined sensory (vision + hearing) loss plus developmental delay produces major functional impact even in "mild" survivors; caregiver-reported burden is high across the spectrum (Bose et al. 2020, PMID:33335840). No ZSD-specific EQ-5D/SF-36 dataset was identified in this search; QOL data are largely qualitative/caregiver-reported rather than standardized instrument-based.

4. Genetic/Molecular Information

Causal genes: The 13 PEX genes listed in §2, all acting via loss-of-function (biallelic) mechanisms. HGNC symbols: PEX1, PEX2, PEX3, PEX5, PEX6, PEX7 (causes the biochemically related but clinically distinct RCDP1, not classic ZSD — see below), PEX10, PEX11B, PEX12, PEX13, PEX14, PEX16, PEX19, PEX26.

Variant classification/type: - Null/loss-of-function variants (large deletions, nonsense, frameshift) — associated with severe phenotype (complete absence of peroxin function). - Missense/hypomorphic variants retaining residual function (e.g., PEX1 p.Gly843Asp) — associated with milder phenotype. - Compound heterozygosity of a null + hypomorphic allele → intermediate phenotype. - Clinical severity correlates with overall genotype/residual peroxin activity rather than which specific PEX gene is mutated — i.e., genotype (allele combination), not locus identity, is the primary determinant. - A notable genetic exception to strict autosomal-recessive inheritance: the PEX6 variant p.Arg860Trp can cause disease in a functionally heterozygous state via allelic expression imbalance (unusual dominant-like mechanism reported in GeneReviews).

Allele frequency in population databases: - PEX1 p.Gly843Asp (rs61750420): gnomAD/general-population allele frequency ≈0.00033 (≈1/3000 alleles); much higher (0.43) among PEX1-mutant disease alleles specifically (ClinVar). - A 2025 population-genetics modeling study estimated PEX1-mediated ZSD births and population prevalence using allele-frequency data (see Genetics in Medicine Open, 2025) — useful for refining historical incidence estimates that likely undercount mild/undiagnosed cases.

Somatic vs. germline: ZSD is exclusively germline (constitutional) — no somatic/mosaic ZSD-associated malignancy mechanism has been described (distinct from unrelated adult hepatocellular carcinoma occasionally reported as a complication in surviving ZSD patients, which is a disease complication, not somatic PEX pathogenesis).

Functional consequences (molecular mechanism of PEX1/PEX6, illustrative): PEX1 and PEX6 are AAA-ATPases that assemble into a heterohexameric complex mediating ATP-dependent extraction and recycling of the ubiquitinated PTS1 receptor PEX5 (and PEX7, the PTS2 receptor) from the peroxisomal membrane back to the cytosol. Loss of PEX1 function traps ubiquitinated PEX5 at the membrane, blocking further rounds of matrix protein import, causing failure to form functional peroxisomes, increased pexophagy, and formation of aberrant "ghost peroxisomes" (membrane remnants devoid of matrix enzymes) (Frontiers/PMC12626956 zebrafish Pex1 model).

Modifier genes: No validated modifier genes beyond the allelic-series (residual-activity) effect described above; ATAD1 has recently been proposed as a candidate modulator of mitochondrial/peroxisomal function in ZSD models (2025 preprint, biorxiv) but is not an established clinical modifier.

Epigenetic information: No disease-specific DNA methylation/histone-modification signature for ZSD was identified in this search; this remains an unexplored area relative to other rare monogenic diseases.

Chromosomal abnormalities: ZSD is a single-gene (biallelic small-variant) disorder; no recurrent large-scale chromosomal rearrangement (aneuploidy/translocation) mechanism is implicated. Deletion/duplication (CNV) analysis of individual PEX genes is part of standard molecular diagnostic algorithms when sequence analysis alone is uninformative (GeneReviews).

5. Environmental Information

ZSD has no infectious, toxin, or lifestyle etiology — it is fully genetic. The only "environmental" considerations relevant to the disease are: - Nutritional/metabolic stress (fasting, intercurrent illness) that can precipitate acute decompensation via unmasking adrenal insufficiency or worsening hepatic dysfunction in patients with residual peroxisomal function. - Dietary DHA (docosahexaenoic acid) status, addressed therapeutically (§12) because peroxisomal dysfunction secondarily depletes endogenous DHA synthesis. No infectious agent is implicated in disease causation or exacerbation.

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream):

Molecular trigger: Biallelic loss-of-function variant in a PEX gene (peroxin) → failure of peroxisomal membrane biogenesis (PEX3/PEX16/PEX19) or failure of the PTS1/PTS2 matrix-protein import machinery (PEX5/PEX7 receptors; PEX13/PEX14 docking complex; PEX2/PEX10/PEX12 RING-peroxin ubiquitination machinery; PEX1/PEX6/PEX26 receptor-recycling AAA-ATPase complex) (GO:0016561 protein import into peroxisome matrix, translocation; GO:0016562 receptor recycling; Reactome R-HSA-9033241 Peroxisomal protein import).
Cellular consequence: Absence of functional (import-competent) peroxisomes, or markedly reduced peroxisome number/size ("peroxisomal ghosts") → global loss of peroxisomal enzymatic function (>50 enzymes normally housed in the organelle).
Biochemical consequence (multiple parallel metabolic failures):
Failure of peroxisomal β-oxidation of very-long-chain fatty acids (VLCFA) → VLCFA accumulation in plasma and tissues (the primary diagnostic biomarker).
Failure of plasmalogen (ether phospholipid) biosynthesis (dihydroxyacetone phosphate acyltransferase / alkyl-DHAP synthase are peroxisomal, PTS2-imported enzymes) → plasmalogen deficiency in erythrocyte membranes and, critically, in myelin, since peroxisomes are the sole site of plasmalogen synthesis.
Failure of bile acid side-chain oxidation → accumulation of toxic C27 bile acid intermediates (di- and trihydroxycholestanoic acid, DHCA/THCA) → hepatotoxicity/cholestasis.
Failure of phytanic/pristanic acid α/β-oxidation → accumulation of branched-chain fatty acids.
Impaired docosahexaenoic acid (DHA) synthesis (a partially peroxisomal pathway) → DHA deficiency, particularly relevant to retina/brain membrane composition.
Elevated pipecolic acid.
Cellular/tissue consequence:
Plasmalogen/myelin deficiency + VLCFA-driven membrane lipid abnormality → impaired oligodendrocyte myelination and neuronal migration defects (GO:0007406 negative regulation of neuroblast proliferation-type processes are affected during migration; cell types: CL:0000128 oligodendrocyte, CL:0000031 neuroblast/radial glia during migration).
Hepatotoxic bile-acid intermediates + VLCFA accumulation → hepatocyte (CL:0000182) injury, cholestasis, and progressive fibrosis (feeds a fibrotic-response-type mechanism in the liver).
VLCFA incorporation into complex membrane lipids of multiple cell types (retinal photoreceptors [CL:0000210], cochlear hair cells [CL:0000202], adrenal cortical cells [CL:1000477 / CL:0002499], renal tubular/podocyte-adjacent epithelium contributing to cyst formation) → activation of inflammatory signaling, oxidative stress, and cell dysfunction/death in each of these tissues.
Mitochondrial dysfunction: recent work shows mislocalized peroxins insert into mitochondria and disturb cristae structure directly, and mitochondrial dysfunction/oxidative stress/excess ROS are increasingly recognized as a secondary, convergent mechanism contributing to neurotoxicity alongside the primary lipid-metabolism defects (EMBO Reports, "The biochemical basis of mitochondrial dysfunction in ZSD"; PMC10652488, MAPK activation & impaired autophagy in ZSD/X-ALD).
Impaired autophagy and abnormal MAPK pathway activation have been reported in patient-derived cells, suggesting broader proteostasis/signaling disruption beyond lipid metabolism alone.
Organism-level manifestation: The combined effect of (a) neuronal migration/myelination failure, (b) hepatocellular injury, (c) adrenocortical dysfunction, (d) sensory (retinal/cochlear) degeneration, and (e) skeletal mineralization defects (chondrodysplasia punctata) produces the multisystem clinical phenotype described in §3, with severity determined by the degree of residual peroxin/peroxisome function.

Suggested GO terms (biological process): GO:0016561 (protein import into peroxisome matrix, translocation), GO:0016562 (receptor recycling), GO:0044721 (substrate release), GO:0006635 (fatty acid beta-oxidation), GO:0006654 (phosphatidic acid biosynthetic process, upstream of plasmalogen synthesis), GO:0042760 (very-long-chain fatty acid catabolic process), GO:0007041 (lysosomal transport — for the secondary autophagy defect), GO:0006979 (response to oxidative stress).

Suggested CL terms (cell types): CL:0000182 (hepatocyte), CL:0000128 (oligodendrocyte), CL:0000210 (photoreceptor cell), CL:0000202 (auditory hair cell), CL:0002499 (adrenal cortex cell) or CL:1000477, CL:0000646 (basal cell / renal tubular epithelial cell as relevant to cyst formation), CL:0000138 (chondrocyte, relevant to chondrodysplasia punctata).

Suggested UBERON terms (see §7).

Molecular profiling / omics: Lipidomic (plasmalogen/VLCFA) and to a lesser extent transcriptomic/proteomic profiling of patient fibroblasts and animal-model tissues have been used to characterize disease mechanism (e.g., mouse retinal pigment epithelium lipidomics in the PEX1-p.Gly844Asp model, biorxiv 2024); no large-scale human single-cell or spatial transcriptomic ZSD atlas was identified in this search — this remains a data gap relative to other rare disease areas.

7. Anatomical Structures Affected

Organ level: - Primary: liver (UBERON:0002107), brain/CNS (UBERON:0000955), adrenal gland (UBERON:0002369), eye/retina (UBERON:0000966 / UBERON:0000970), inner ear/cochlea (UBERON:0001846), kidney (UBERON:0002113), skeleton — long bones and patella (UBERON:0002438 femur; UBERON:0011595 patella). - Secondary/complications: cardiovascular system (structural cardiac anomalies), teeth (enamel — amelogenesis imperfecta), skin (occasionally), gastrointestinal tract (feeding dysfunction as a downstream neuro-motor consequence). - Body systems involved: nervous, hepatobiliary, endocrine, sensory (visual, auditory), skeletal, renal, and — to a lesser, secondary extent — cardiovascular.

Tissue and cell level: - Hepatocytes (CL:0000182) — cholestasis, steatosis, fibrosis. - Oligodendrocytes/myelin (CL:0000128) — leukodystrophy in the intermediate/progressive forms. - Neurons undergoing migration (radial glia-guided cortical neuroblasts) — neuronal migration defects (polymicrogyria/pachygyria). - Retinal photoreceptors and RPE (CL:0000210; CL:0002586 retinal pigment epithelial cell) — progressive retinopathy. - Cochlear hair cells (CL:0000202) — sensorineural hearing loss. - Adrenal cortical cells (zona fasciculata/reticularis) — adrenal insufficiency. - Chondrocytes of the epiphyseal growth plate — chondrodysplasia punctata. - Renal tubular epithelium — cortical microcysts.

Subcellular level (GO Cellular Component): - Peroxisome (GO:0005777) and peroxisomal membrane (GO:0005778) — the primary organelle defect. - Peroxisomal matrix (GO:0005782). - Secondary mitochondrion (GO:0005739) involvement via peroxin mislocalization and cristae disruption. - Endoplasmic reticulum contribution to peroxisomal membrane biogenesis (pre-peroxisomal vesicle origin), relevant to PEX3/PEX16/PEX19 mechanism.

Localization/laterality: Disease manifestations are bilateral/symmetric and systemic — no lateralization pattern is described (consistent with a metabolic, non-focal-lesion disease process).

8. Temporal Development

Onset: - Severe (classic "Zellweger syndrome"): congenital/neonatal onset — symptomatic at birth or within the first days of life. - Intermediate ("NALD"): infantile/early childhood onset. - Mild ("IRD" and beyond): later childhood, adolescent, or even adult recognition — onset pattern is insidious, often first suspected because of progressive sensory (vision/hearing) decline rather than an acute neonatal presentation.

Progression: - Severe form: rapid, uniformly fatal — median survival well under 1 year (mortality before age 2 in 95.7% of a severe natural-history cohort, PMID:35741019). - Intermediate form: progressive but slower — developmental delay, progressive vision/hearing loss, evolving hepatic and adrenal dysfunction over years; ~77% of children who survive the first year with a "non-progressive" trajectory reach school age (GeneReviews). - Mild form: slowly progressive, dominated by sensory (retinal, cochlear) degeneration over years-to-decades; cognition and mobility may remain largely preserved into adulthood, though hearing/vision loss is essentially universal and progressive even here. - Disease course is best described as chronic and progressive across the spectrum, with the rate of progression (not the presence of progression) distinguishing severity tiers; it is not classically relapsing-remitting.

Patterns: - No spontaneous remission is described; symptomatic/supportive treatments (e.g., cholic acid for cholestasis) can produce biochemical and some clinical improvement but do not reverse the underlying peroxisomal defect. - Critical periods: the neonatal/early-infancy window is the critical period for neuronal migration (in utero/early perinatal) — meaning the most severe structural brain malformations are fixed prenatally and not amenable to postnatal intervention, whereas ongoing myelination, retinal, cochlear, hepatic, and adrenal deterioration in milder patients represent a longer therapeutic window potentially targetable by early biochemical/gene-directed intervention (rationale behind newborn-screening-driven early diagnosis efforts, §10 and §13).

9. Inheritance and Population

Epidemiology: - US incidence: ~1/50,000 live births (historical estimate, now understood to likely undercount mild/atypical cases). - Recent New York state confirmed incidence (via newborn screening-adjacent surveillance): ~1/133,000 births. - Japan: ~1/500,000 births (absence of common European PEX1 founder alleles). - Saguenay–Lac-Saint-Jean, Quebec (French-Canadian founder population): ~1/12,000 births — one of the highest reported incidences worldwide, due to a PEX6 founder mutation (PMC3483250). - A 2025 population-genetics modeling paper specifically models PEX1-mediated ZSD births and population prevalence to refine these estimates (GIM Open 2025). - Roughly ~30% of ZSD patients carry null variants (nonfunctional PEX protein) with congenital brain malformations and infant lethality; the majority (~70%) have an intermediate-to-milder phenotype from residual PEX protein function.

Inheritance pattern: Autosomal recessive for all 13 PEX genes (with the rare functional-heterozygote exception noted for PEX6 p.Arg860Trp, §4).

Penetrance: Effectively complete/full penetrance for biallelic loss-of-function genotypes; expressivity (not penetrance per se) is the major source of variability.

Expressivity: Highly variable, driven primarily by residual peroxin activity from the specific allele combination (§4), ranging from neonatal-lethal to adult-onset sensory-predominant disease.

Genetic anticipation: Not applicable — ZSD is not a repeat-expansion disorder.

Germline mosaicism: Not specifically documented as a recurring feature of ZSD in the literature reviewed; standard autosomal-recessive recurrence risk counseling (25% affected, 50% carrier, 25% unaffected per sibling of two carrier parents) applies (GeneReviews).

Founder effects: PEX1 p.Gly843Asp and p.Ile700Tyrfs*42 (European founder alleles); PEX6 founder variant (French-Canadian/Quebec, and possibly Mixteco); population-specific allele spectra explain much of the observed geographic incidence variation.

Consanguinity role: Significant contributor in high-consanguinity populations (e.g., Saudi Arabia), where ZSD (along with many other autosomal-recessive diseases) is more frequently observed due to increased homozygosity.

Carrier frequency: Not precisely established as a single population-wide number in the sources reviewed, but individual founder-allele carrier frequencies can be substantial in specific populations (e.g., the French-Canadian PEX6 founder variant).

Population demographics: - No strong sex predilection is reported (autosomal recessive disease; consistent with a ~1:1 male:female ratio). - Geographic/ethnic variation is driven by founder-allele distribution (European vs. Japanese vs. French-Canadian vs. Middle Eastern/consanguineous populations) rather than intrinsic biological sex- or ancestry-linked susceptibility beyond allele frequency effects. - Age distribution of diagnosed individuals spans neonate through adult, reflecting the full severity spectrum, though the majority of historically diagnosed cases are neonatal/infantile because biochemical screening (VLCFA) is most sensitive in that group; milder/adult cases are increasingly recognized with molecular testing and newborn screening spillover (§10).

10. Diagnostics

Biochemical/clinical laboratory tests: - Plasma/serum very-long-chain fatty acids (VLCFA) — elevated; the classic first-line screening test, though normal/equivocal in some mild cases, a key diagnostic pitfall. - Erythrocyte plasmalogen levels (RBC C16/C18 plasmalogens) — reduced. - Phytanic acid and pristanic acid — elevated. - Pipecolic acid (plasma/urine) — elevated. - Bile acid intermediates (DHCA/THCA) — elevated in plasma and urine. - C26:0-lysophosphatidylcholine (C26:0-LPC) and C26:0-carnitine — newer, more sensitive/specific dried-blood-spot biomarkers, notably validated as secondary findings from X-ALD newborn screening programs: in California's X-ALD NBS program (screening via C26:0-LPC since 2016), 9 patients screened positive for elevated C26:0-LPC between 2016–2022 who did not have X-ALD, of whom 7 were subsequently diagnosed with ZSD via biallelic PEX variants — demonstrating C26:0-LPC's utility as an incidental ZSD-detection tool within an ALD-focused screening program (2024 publication, PMC11275617; Klouwer/Waterham C26:0-LPC and C26:0-carnitine evaluation, PMID:28677031). - Plasma C24:0- and C26:0-lysophosphatidylcholines more broadly proposed as reliable biomarkers for peroxisomal β-oxidation disorders generally (PMC10910329).

Genetic testing: - Multigene PEX panel sequencing is the recommended first-tier molecular approach (rather than single-gene sequential testing), given 13 causal genes. - Sequence analysis detects ~98% of PEX1 variants; deletion/duplication (CNV) analysis captures most of the remainder. - Exome/genome sequencing is appropriate when the clinical presentation does not clearly localize to ZSD (e.g., an atypical/mild presentation overlapping with Usher syndrome or other conditions). - Diagnosis is established by biallelic pathogenic/likely-pathogenic variants in a single PEX gene in the appropriate biochemical/clinical context.

Imaging: - Brain MRI — neuronal migration defects (polymicrogyria, pachygyria) in severe neonatal form; progressive white-matter changes (leukodystrophy) in intermediate/childhood forms. - Renal ultrasound — cortical microcysts. - Skeletal radiography — chondrodysplasia punctata (stippled epiphyses). - Liver ultrasound/elastography (fibroscan) — for ongoing hepatic surveillance.

Functional/electrophysiologic tests: - EEG — abnormal in virtually all severe-category patients. - Audiometry — for sensorineural hearing loss surveillance (annual, per GeneReviews management recommendations). - Electroretinography (ERG) — documents progressive retinal dystrophy.

Biopsy/pathology: Historically, cultured skin fibroblasts were used for biochemical complementation/functional studies (peroxisome import assays, immunofluorescence for peroxisomal marker proteins) — now largely supplanted by molecular sequencing but still useful for variant functional characterization (e.g., confirming pathogenicity of novel PEX1/PEX13 missense variants).

Clinical diagnostic criteria: No formal DSM/ICD-style operational criteria beyond the recognized triad of biochemical abnormality + compatible clinical phenotype + confirmatory biallelic PEX genotype (GeneReviews-based diagnostic algorithm).

Differential diagnosis: - Neonatal hypotonic/dysmorphic infant: trisomy 21, Prader-Willi syndrome, congenital myopathies (spinal muscular atrophy, congenital myotonic dystrophy type 1, X-linked myotubular myopathy, multiminicore myopathy). - Later/milder presentation (progressive sensory loss + mild developmental delay): Usher syndrome types I/II, Leber congenital amaurosis, Cockayne syndrome, other congenital leukodystrophies — importantly, "mild forms of PBD can be a differential diagnosis of Usher syndrome," and comprehensive mutation screening including PEX genes is recommended in patients with combined cognitive/visual/hearing impairment of uncertain cause (search synthesis; GeneReviews). - Distinct related peroxisomal disorders that must be distinguished biochemically/molecularly: rhizomelic chondrodysplasia punctata type 1 (RCDP1, PEX7) — a peroxisomal assembly defect restricted to PTS2-pathway matrix proteins (AGPS, PHYH), with a biochemically, cellularly, and clinically distinct phenotype from classic ZSD, despite shared plasmalogen deficiency; X-linked adrenoleukodystrophy (ABCD1) — a peroxisomal transporter (not biogenesis) defect causing VLCFA accumulation without global peroxisome loss.

Screening: - Newborn screening: ZSD is not yet a primary RUSP (Recommended Uniform Screening Panel) condition in the US, but is being incidentally detected via X-ALD newborn screening (C26:0-LPC), an important and expanding secondary-finding pathway (California data above). - Carrier/prenatal/preimplantation genetic screening: Offered to at-risk families once biallelic familial variants are known; prenatal diagnosis is possible by DNA testing (if variants known) or biochemical testing in cultured amniocytes/chorionic villi (if biochemical defect previously confirmed in an affected relative's fibroblasts). Preimplantation genetic diagnosis for Zellweger syndrome has been reported (ScienceDirect PGD reference).

11. Outcome/Prognosis

Survival and mortality: - Severe form: mortality before age 2 in 95.7% of a natural-history cohort (n=23); classically described as death within the first year of life without significant developmental progress. - Intermediate and mild forms: substantially better survival; ~77% of children surviving the first year with a non-progressive course reach school age (GeneReviews). Survival differences across severe/intermediate/mild categories were statistically significant (log-rank p<0.001) in the largest meta-analysis/chart-review study (PMID:35741019). - Some mildly affected individuals survive into adulthood, though with progressive sensory deficits and other systemic complications (Klouwer 2015 "adulthood" cohort, PMC4710674).

Morbidity/functional outcomes: - Even among longer-surviving (intermediate/mild) patients, near-universal progressive vision and hearing loss is the dominant chronic morbidity. - Developmental delay is common in intermediate disease (97.5%) but much less so (16.3% seizure rate as a proxy) in mild disease, where most patients achieve independent ambulation (87.8%) and full-sentence speech (71.7%). - Adrenal insufficiency, if undiagnosed, poses an ongoing acute-decompensation/mortality risk across the spectrum and is likely underdiagnosed in adolescents/adults. - Hepatic disease can progress to fibrosis/portal hypertension in surviving patients; hepatocellular carcinoma has been reported as a rare late complication in adults.

Complications: Recurrent infections/aspiration (from hypotonia/feeding dysfunction), fractures (from osteopenia), bleeding (vitamin-K-responsive coagulopathy from cholestasis), adrenal crisis, progressive blindness/deafness.

Prognostic factors: The single strongest prognostic determinant is genotype/residual peroxin activity (null vs. hypomorphic allele combination), which directly predicts which severity tier (and hence survival/functional trajectory) a patient falls into (§4, §9).

12. Treatment

There is no disease-modifying/curative therapy approved for ZSD; management is supportive/symptomatic, organ-system-directed, with active experimental gene-therapy research.

Pharmacotherapy: - Cholic acid (Cholbam™, FDA-approved for bile acid synthesis disorders including peroxisomal disorders) — oral primary bile acid that restores physiologic feedback inhibition on hepatic bile-acid synthesis, thereby suppressing production of hepatotoxic C27 bile-acid intermediates. Clinical trials/case series show reduced AST/ALT, reduced plasma/urinary bile-acid intermediates, improved weight gain, and improved survival in treated patients, though caution is needed in advanced liver disease due to potential hepatotoxicity of the therapy itself in that setting (PMID:27469511; long-term case reports in Case Reports in Gastroenterology). A long-term personalized-dosing safety study is ongoing (planned through Dec 2027). - Docosahexaenoic acid (DHA) supplementation — rationale: peroxisomal DHA-synthesis deficiency. A randomized, double-blind, placebo-controlled trial (100 mg/kg/day, 50 patients enrolled) found DHA supplementation did not reduce C26:0 levels and had inconsistent effects on visual outcomes, despite earlier small-cohort reports suggesting improved muscle tone/visual function in newborns (PMC3013498; PMID:8729110). Net evidence is not strongly supportive of DHA as an effective disease-modifying agent, though it remains used empirically in some clinical settings. - Betaine — investigated in a clinical trial context for peroxisome biogenesis disorders (NCT01838941), rationale/results not detailed in sources reviewed here. - Anti-seizure medications — standard symptomatic management for the seizure phenotype. - Glucocorticoid/mineralocorticoid replacement — for confirmed adrenal insufficiency. - Fat-soluble vitamin supplementation (A, D, E, K) — for malabsorption secondary to cholestasis. - Bisphosphonates/vitamin D — considered for osteopenia management.

Advanced/experimental therapeutics (gene therapy — active research, not yet clinically approved): - AAV8-mediated PEX1 gene augmentation (retinal-directed) in the PEX1-p.Gly844Asp mouse model improved visual function, retinal structure/response, and biochemical metabolites — "the first testing of gene therapy to treat a peroxisome biogenesis disorder," providing proof-of-concept for gene-augmentation approaches; this program had progressed enough by 2024 to attract venture investment and move toward clinical translation (Mol Ther Methods Clin Dev, PMC8516995; scientist.com webinar). - In vivo gene editing (CRISPR-based correction of a PEX1 mutation) — a 2025–2026 preclinical program corrected the disease-causing mutation in mouse models and human patient cells, returning liver tissue to near-normal function; this used the same base-editing/gene-editing platform later adapted for the high-profile "Baby KJ" personalized gene-editing case reported in 2025, and researchers are now exploring delivery modalities that extend beyond liver to the CNS for broader multi-organ benefit (hearing, vision) (JAX news, April 2026; biorxiv 2026 preprint). - No RNA-based (ASO/siRNA), cell-therapy, or approved small-molecule targeted therapy for ZSD itself was identified in this search (as distinct from the ASO-based therapies used in unrelated peroxisomal-transporter disease X-ALD, which is molecularly distinct — ABCD1, not a PEX biogenesis gene).

Surgical/interventional: Cataract extraction; gastrostomy tube placement for feeding difficulty/dysphagia; occasional orthopedic intervention for skeletal complications.

Supportive/rehabilitative care: - Hearing aids/cochlear implantation consideration for sensorineural hearing loss. - Physical, occupational, and speech therapy. - Nutritional support/feeding therapy. - Dental surveillance/intervention for amelogenesis imperfecta (every 6 months per management guidelines).

Surveillance schedule (per GeneReviews management recommendations): growth/nutrition at each visit; annual audiology; annual ophthalmology; annual liver function tests + ultrasound/fibroscan; ACTH/cortisol by age 1 year then annually; dental every 6 months; annual urine oxalate-to-creatinine ratio; head MRI as clinically indicated.

Suggested MAXO terms: MAXO:0000004 (surgical procedure — cataract extraction), MAXO:0000011 (physical therapy), MAXO:0000088 (dietary intervention — DHA/vitamin supplementation), MAXO:0000950 (supportive care); pharmacotherapy of cholic acid would use the generic NCIT:C15986 (Pharmacotherapy) treatment-term pattern with therapeutic_agent bound to the specific compound (cholic acid; CHEBI:16359).

Treatment strategy/personalized medicine: Management is explicitly organ-system-by-organ-system and severity-tiered — i.e., a personalized surveillance/intervention algorithm keyed to where a given patient falls on the severity spectrum, rather than a single uniform treatment algorithm, reflecting the absence of a disease-modifying therapy.

13. Prevention

Primary prevention: Not possible in the traditional sense (no modifiable risk factor); the only "primary prevention" avenue is reproductive, via carrier screening and reproductive decision-making (prenatal diagnosis, preimplantation genetic diagnosis) in families with a known PEX pathogenic variant, or in populations with elevated carrier frequency (e.g., pre-conception expanded carrier screening in consanguineous populations, as illustrated by an Afghan-descent consanguineous cohort study referenced in this search — PMC12167801).
Secondary prevention (early detection): Incidental detection through X-ALD newborn screening (C26:0-LPC, C26:0-carnitine) is an emerging, real-world secondary-prevention pathway that identifies ZSD before overt clinical presentation, enabling earlier initiation of supportive therapy (cholic acid, endocrine/audiology/ophthalmology surveillance) and more accurate genetic counseling.
Tertiary prevention: The entire structured surveillance program described in §12 (annual audiology, ophthalmology, hepatic, endocrine, renal, dental monitoring) functions as tertiary prevention — aiming to catch and manage organ-specific complications before they cause irreversible harm (e.g., catching adrenal insufficiency before crisis, catching hearing/vision loss early enough for assistive intervention).
Genetic counseling: Recommended for affected individuals, known carriers, and at-risk relatives, covering recurrence risk (25%/50%/25% per sibling for AR inheritance), reproductive options, and prenatal/preimplantation testing availability once familial variants are known.
No immunization/vaccine strategy is applicable (non-infectious, genetic disease).
No specific environmental/public-health intervention applies beyond population-level carrier-screening programs in high-risk/consanguineous communities.

14. Other Species / Natural Disease

Taxonomy: No well-documented naturally occurring (spontaneous) Zellweger-spectrum-equivalent disease was identified in companion animals (dogs/cats) or livestock in the sources reviewed here; OMIA (Online Mendelian Inheritance in Animals) was not directly queryable in this search session, and general veterinary-genetics sources referenced in the search did not specifically document a natural PEX-gene disease in domestic species. This should be treated as absence of evidence found, not confirmed absence — a direct OMIA database query is recommended before asserting no natural animal disease exists.
Gene orthologs: PEX1, PEX6, PEX5, PEX2, PEX7, etc. are broadly conserved across vertebrates and even into yeast (where PEX gene biology was originally characterized), reflected in the extensive use of mouse, zebrafish, and even Drosophila/yeast models (below) — i.e., the mechanism is deeply evolutionarily conserved even though naturally occurring veterinary disease is not well documented.
Comparative biology: The core peroxisomal biogenesis/import pathway (PTS1/PTS2 receptors, RING-peroxin ubiquitination, AAA-ATPase recycling) is conserved from yeast to humans, which is precisely why yeast and Drosophila genetics originally defined much of PEX gene function before human disease genes were identified.
Zoonotic potential/transmission: Not applicable — ZSD is a non-transmissible monogenic disease.

15. Model Organisms

Mouse models: - Constitutive knockouts of Pex5, Pex2, and Pex11β recapitulate the severe end of the spectrum but die shortly after birth due to profound hypotonia/respiratory failure, which has historically limited postnatal disease-progression studies (Nature Genetics 1997, "A mouse model for Zellweger syndrome"). - PEX1-G844D (Gly844Asp) knock-in mouse — models the mild end of the human spectrum (analogous to the common human p.Gly843Asp hypomorphic allele) and is viable long-term, recapitulating growth retardation, fatty liver, retinopathy, cochlear hair-cell degeneration, and hearing loss — making it "a robust pre-clinical model for mild Zellweger spectrum disorder" used in longitudinal natural-history and therapeutic (AAV gene-therapy) studies (ScienceDirect longitudinal study; AAV-PEX1 gene augmentation study, PMC8516995; 2024 RPE lipidomics biorxiv; 2025 liver-disease-progression biorxiv). - A Pex7-deficient mouse series exists for the related but distinct disorder RCDP1 (not classic ZSD), correlating biochemical/neurobehavioral markers with genotype severity (PMC9310236).

Zebrafish models: - A Pex1 loss-of-function zebrafish model was recently shown to be viable (unlike the severe mouse knockouts) and to recapitulate hallmarks of ZSD, offering a tractable, higher-throughput vertebrate system for mechanistic and drug-screening studies (Frontiers in Molecular Neuroscience 2025, PMC12626956).

Invertebrate/cellular models: - Drosophila models have been used to dissect substrate-channeling effects on phospholipids and sphingolipids in peroxisomal biogenesis disorders, complementing vertebrate models for specific lipidomic mechanism questions (PMC12157166); Drosophila and mouse models have also been used to show that peroxisomal biogenesis is genetically and biochemically linked to carbohydrate metabolism (PMC5480855). - Patient-derived fibroblasts remain a standard cellular model for functional variant classification (e.g., confirming the ~15% residual activity of PEX1 p.Gly843Asp) and for studying secondary mechanisms such as MAPK pathway activation and impaired autophagy (PMC10652488). - Yeast (historically Saccharomyces cerevisiae, Pichia pastoris) was the original discovery system for most PEX genes and remains used for basic peroxin biochemistry (e.g., PEX14 phosphorylation and matrix-protein import studies).

Phenotype recapitulation and limitations: - Severe-knockout mice (Pex5/Pex2/Pex11β) faithfully model lethality and hypotonia but cannot be used to study chronic, progressive organ pathology because of neonatal death — a key model limitation. - The PEX1-G844D mouse is currently the best-characterized long-term model, closely recapitulating the human mild ZSD phenotype (hearing loss, retinopathy, liver disease) and serving as the primary preclinical platform for the AAV-gene-therapy and gene-editing programs described in §12. - The new viable zebrafish Pex1 model is positioned as a complementary, more scalable system for hallmark-recapitulation and prospective drug/gene-therapy screening. - No model fully recapitulates the entire human severity spectrum in one organism; researchers instead use different models for different severity tiers (severe knockout mice for the lethal end; PEX1-G844D mice and the new zebrafish model for the mild/intermediate end).

Model databases/resources: MGI (Mouse Genome Informatics) for Pex-gene mouse alleles; ZFIN for the zebrafish Pex1 model; FlyBase for the Drosophila peroxisomal-biogenesis lines referenced above.

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References

Deep Research

Zellweger Spectrum Disorder (ZSD): Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

Neurological

Craniofacial / Dysmorphic

Hepatic

Endocrine

Ocular

Auditory

Skeletal

Renal

Cardiac

Gastrointestinal/Growth

Functional/Behavioral (milder end of spectrum)

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

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