SCO1-Related COX Deficiency

Mendelian MONDO:0033636 Pathograph 8 Show in embeddings browser Mitochondrial Disease Inborn Error of Metabolism

SCO1-related COX deficiency (mitochondrial complex IV deficiency nuclear type 4, MC4DN4) is a nuclear form of isolated cytochrome c oxidase (COX, Complex IV) deficiency caused by biallelic variants in SCO1, a copper-delivery metallochaperone. The classic presentation is neonatal-onset hepatic failure and encephalopathy with lactic acidosis; the phenotypic spectrum has been expanded to include developmental and epileptic encephalopathy with progressive hypopituitarism. It conforms to the conserved Complex IV assembly deficiency mechanism, with the assembly defect localized to copper delivery and dominant hepatic, neurologic, and endocrine involvement.

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2
Pathophys.
5
Phenotypes
8
Pathograph
1
Genes
1
Medical Actions
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE ENDOCRINOLOGY METABOLISM
Mechanistic Nosology
mitochondrial disease
ICIMD (Inherited Metabolic Disorders)
complex iv subunits and assembly factors
⚙

Pathophysiology

2
SCO1 Loss and Defective Copper Delivery to COX
Biallelic SCO1 variants impair copper delivery to the COX CuA center, preventing assembly of a functional Complex IV holoenzyme.
SCO1 hgnc:10603 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves SCO1 (hgnc:10603). hgnc:10603 is a gene from the HUGO Gene Nomenclature Committee.
copper ion transport GO:0006825 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased copper ion transport (GO:0006825). GO:0006825 is a biological process from the Gene Ontology. ↓ DECREASED mitochondrial respiratory chain complex IV assembly GO:0033617 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased mitochondrial respiratory chain complex IV assembly (GO:0033617). GO:0033617 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Terminal Electron Transfer and ATP Synthesis Failure of CuA assembly yields a catalytically inactive enzyme.
Show evidence (1 reference)
PMID:39214134 SUPPORT Human Clinical
"Mitochondrial complex IV deficiency nuclear type 4 (MC4DN4) is a form of COX deficiency associated with pathogenic variants in the SCO1 gene."
Confirms SCO1 variants cause MC4DN4, a nuclear copper-delivery COX deficiency.
Impaired Terminal Electron Transfer and ATP Synthesis
Loss of functional COX blocks electron transfer from cytochrome c to oxygen and proton pumping, collapsing oxidative ATP synthesis, with prominent hepatic and neurologic involvement.
hepatocyte CL:0000182 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves hepatocyte (CL:0000182). CL:0000182 is a cell type from the Cell Ontology.
mitochondrial electron transport, cytochrome c to oxygen GO:0006123 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased mitochondrial electron transport, cytochrome c to oxygen (GO:0006123). GO:0006123 is a biological process from the Gene Ontology. ↓ DECREASED ATP synthesis coupled electron transport GO:0042775 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased ATP synthesis coupled electron transport, annotated with mitochondrial ATP synthesis coupled electron transport (GO:0042775). GO:0042775 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Hepatic failure Energy failure in hepatocytes drives neonatal hepatic failure. Note that the PMID:11013136 abstract states the hepatic presentation only in its title, so no exact-quote snippet from the cached abstract supports this edge; evidence is deliberately omitted rather than sourced from a title.
Encephalopathy Energy deficit in the CNS produces encephalopathy.
Seizures CNS energy failure in the developmental and epileptic encephalopathy phenotype contributes to seizures.
Hypopituitarism Multisystem mitochondrial energy failure can involve the hypothalamic-pituitary axis, producing hypopituitarism.
Lactic acidosis Impaired oxidative phosphorylation shifts pyruvate metabolism toward lactate accumulation, producing lactic acidosis.
Show evidence (1 reference)
PMID:10545952 SUPPORT Human Clinical
"Mammalian cytochrome c oxidase (COX) catalyses the transfer of reducing equivalents from cytochrome c to molecular oxygen and pumps protons across the inner mitochondrial membrane."
Defines the terminal electron-transfer and proton-pumping function lost in SCO1-related COX deficiency.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for SCO1-Related COX Deficiency Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

5
Digestive 1
Hepatic failure HP:0001399 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hepatic failure (HP:0001399). HP:0001399 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11013136 SUPPORT Human Clinical
"neonatal-onset hepatic failure and encephalopathy"
The report describes SCO1 mutations in COX deficiency presenting with neonatal-onset hepatic failure.
Metabolism 1
Lactic acidosis HP:0003128 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Lactic acidosis (HP:0003128). HP:0003128 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19682572 SUPPORT Other
"Human diseases associated with COX deficiency including encephalomyopathies, Leigh syndrome, hypertrophic cardiomyopathies, and fatal lactic acidosis are caused by mutations in COX subunits or assembly factors."
Lactic acidosis is a recognized manifestation of COX deficiency.
Nervous System 2
Encephalopathy HP:0001298 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Encephalopathy (HP:0001298). HP:0001298 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11013136 SUPPORT Human Clinical
"neonatal-onset hepatic failure and encephalopathy"
Encephalopathy is a core feature of SCO1-related COX deficiency.
Seizures HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizures, annotated with Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39214134 SUPPORT Human Clinical
"We describe three patients with MC4DN4 with developmental and epileptic encephalopathy (DEE), hypopituitarism, and SCO1 pathogenic variants."
Documents developmental and epileptic encephalopathy in SCO1/MC4DN4.
Other 1
Hypopituitarism HP:0040075 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypopituitarism (HP:0040075). HP:0040075 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39214134 SUPPORT Human Clinical
"We describe three patients with MC4DN4 with developmental and epileptic encephalopathy (DEE), hypopituitarism, and SCO1 pathogenic variants."
Documents progressive hypopituitarism in the expanded SCO1/MC4DN4 phenotype.
🧬

Genetic Associations

1
SCO1 pathogenic variants causing MC4DN4
Gene: SCO1 hgnc:10603 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SCO1 (hgnc:10603). hgnc:10603 is a gene from the HUGO Gene Nomenclature Committee.
Autosomal recessive
Show evidence (1 reference)
PMID:39214134 SUPPORT Human Clinical
"Mitochondrial complex IV deficiency nuclear type 4 (MC4DN4) is a form of COX deficiency associated with pathogenic variants in the SCO1 gene."
Identifies SCO1 as the causal gene for MC4DN4.
💊

Medical Actions

1
Supportive and Metabolic Care
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
No curative therapy; supportive management of hepatic failure, seizures, endocrine deficits, and lactic acidosis.
{ }

Source YAML

click to show 
name: SCO1-Related COX Deficiency
category: Mendelian
creation_date: "2026-05-30T00:00:00Z"
synonyms:
- SCO1 deficiency
- Mitochondrial complex IV deficiency, nuclear type 4
- MC4DN4
- SCO1-related cytochrome c oxidase deficiency
description: >
  SCO1-related COX deficiency (mitochondrial complex IV deficiency nuclear type
  4, MC4DN4) is a nuclear form of isolated cytochrome c oxidase (COX, Complex
  IV) deficiency caused by biallelic variants in SCO1, a copper-delivery
  metallochaperone. The classic presentation is neonatal-onset hepatic failure
  and encephalopathy with lactic acidosis; the phenotypic spectrum has been
  expanded to include developmental and epileptic encephalopathy with
  progressive hypopituitarism. It conforms to the conserved Complex IV assembly
  deficiency mechanism, with the assembly defect localized to copper delivery
  and dominant hepatic, neurologic, and endocrine involvement.
disease_term:
  preferred_term: SCO1-related COX deficiency (MC4DN4)
  term:
    id: MONDO:0033636
    label: mitochondrial complex IV deficiency, nuclear type 4
parents:
- Mitochondrial Disease
- Inborn Error of Metabolism
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      Mendelian, autosomal recessive nuclear-gene mitochondrial disorder; Harrison's
      covers primary mitochondrial disease under the genetics/environment Part.
  - classification_value: ENDOCRINOLOGY_METABOLISM
    notes: >-
      An inborn error of energy metabolism presenting with lactic acidosis, and
      with progressive hypopituitarism in the expanded MC4DN4 spectrum.
  mechanistic_category:
  - classification_value: mitochondrial disease
    notes: >-
      Nuclear-encoded defect of mitochondrial respiratory chain Complex IV
      biogenesis; a primary mitochondrial disease.
  icimd_category:
  - classification_value: complex_iv_subunits_and_assembly_factors
    notes: >-
      ICIMD (Ferreira et al. 2021, PMID:33340416): group "Nuclear-encoded complex IV
      subunit and assembly factor defects" under category "Disorders of
      nuclear-encoded oxidative phosphorylation". SCO1 is a nuclear-encoded copper
      metallochaperone required for metallation of the COX CuA centre.
pathophysiology:
- name: SCO1 Loss and Defective Copper Delivery to COX
  conforms_to: "complex_iv_assembly_deficiency#Complex IV Biogenesis Failure"
  description: >
    Biallelic SCO1 variants impair copper delivery to the COX CuA center,
    preventing assembly of a functional Complex IV holoenzyme.
  genes:
  - preferred_term: SCO1
    term:
      id: hgnc:10603
      label: SCO1
  biological_processes:
  - preferred_term: copper ion transport
    term:
      id: GO:0006825
      label: copper ion transport
    modifier: DECREASED
  - preferred_term: mitochondrial respiratory chain complex IV assembly
    term:
      id: GO:0033617
      label: mitochondrial respiratory chain complex IV assembly
    modifier: DECREASED
  evidence:
  - reference: PMID:39214134
    reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mitochondrial complex IV deficiency nuclear type 4 (MC4DN4) is a form of COX deficiency associated with pathogenic variants in the SCO1 gene.
    explanation: Confirms SCO1 variants cause MC4DN4, a nuclear copper-delivery COX deficiency.
  downstream:
  - target: Impaired Terminal Electron Transfer and ATP Synthesis
    causal_link_type: DIRECT
    description: Failure of CuA assembly yields a catalytically inactive enzyme.
    evidence:
    - reference: PMID:11013136
      reference_title: "Mutations of the SCO1 gene in mitochondrial cytochrome c oxidase deficiency with neonatal-onset hepatic failure and encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: This proline, adjacent to the CxxxC copper-binding domain of SCO1, is likely to play a crucial role in the tridimentional structure of the domain.
      explanation: Locates the pathogenic SCO1 missense change in the copper-binding domain, tying loss of copper delivery to the resulting isolated COX deficiency.
- name: Impaired Terminal Electron Transfer and ATP Synthesis
  conforms_to: "complex_iv_assembly_deficiency#Impaired Terminal Electron Transfer and ATP Synthesis"
  description: >
    Loss of functional COX blocks electron transfer from cytochrome c to oxygen
    and proton pumping, collapsing oxidative ATP synthesis, with prominent
    hepatic and neurologic involvement.
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  biological_processes:
  - preferred_term: mitochondrial electron transport, cytochrome c to oxygen
    term:
      id: GO:0006123
      label: mitochondrial electron transport, cytochrome c to oxygen
    modifier: DECREASED
  - preferred_term: ATP synthesis coupled electron transport
    term:
      id: GO:0042775
      label: mitochondrial ATP synthesis coupled electron transport
    modifier: DECREASED
  evidence:
  - reference: PMID:10545952
    reference_title: "Fatal infantile cardioencephalomyopathy with COX deficiency and mutations in SCO2, a COX assembly gene."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mammalian cytochrome c oxidase (COX) catalyses the transfer of reducing equivalents from cytochrome c to molecular oxygen and pumps protons across the inner mitochondrial membrane.
    explanation: Defines the terminal electron-transfer and proton-pumping function lost in SCO1-related COX deficiency.
  downstream:
  - target: Hepatic failure
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Energy failure in hepatocytes drives neonatal hepatic failure. Note that the
      PMID:11013136 abstract states the hepatic presentation only in its title, so
      no exact-quote snippet from the cached abstract supports this edge; evidence
      is deliberately omitted rather than sourced from a title.
  - target: Encephalopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Energy deficit in the CNS produces encephalopathy.
    evidence:
    - reference: PMID:39214134
      reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We describe three patients with MC4DN4 with developmental and epileptic encephalopathy (DEE), hypopituitarism, and SCO1 pathogenic variants.
      explanation: Reports encephalopathy in three genetically confirmed MC4DN4 patients, downstream of the SCO1 Complex IV defect.
  - target: Seizures
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: CNS energy failure in the developmental and epileptic encephalopathy phenotype contributes to seizures.
    evidence:
    - reference: PMID:39214134
      reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Our findings expand knowledge of phenotypic variability in MC4DN4 and suggest that SCO1 is a candidate gene for genetic hypopituitarism and DEE.
      explanation: Names SCO1 as a candidate gene for developmental and epileptic encephalopathy, supporting the edge to seizures.
  - target: Hypopituitarism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Multisystem mitochondrial energy failure can involve the hypothalamic-pituitary axis, producing hypopituitarism.
    evidence:
    - reference: PMID:39214134
      reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Pituitary deficiency in these patients progressively worsened and mainly involved growth hormone secretion and thyroid function.
      explanation: Documents progressive pituitary failure in MC4DN4 patients, supporting the hypothalamic-pituitary arm of the multisystem energy failure.
  - target: Lactic acidosis
    causal_link_type: DIRECT
    description: Impaired oxidative phosphorylation shifts pyruvate metabolism toward lactate accumulation, producing lactic acidosis.
    evidence:
    - reference: PMID:19682572
      reference_title: "Cytochrome c oxidase deficiency: patients and animal models."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Human diseases associated with COX deficiency including encephalomyopathies, Leigh syndrome, hypertrophic cardiomyopathies, and fatal lactic acidosis are caused by mutations in COX subunits or assembly factors.
      explanation: Review places lactic acidosis downstream of COX deficiency caused by assembly-factor mutations, the lesion class SCO1 belongs to.
phenotypes:
- name: Hepatic failure
  description: Neonatal-onset hepatic failure, a classic feature of SCO1-related COX deficiency.
  phenotype_term:
    preferred_term: Hepatic failure
    term:
      id: HP:0001399
      label: Hepatic failure
  evidence:
  - reference: PMID:11013136
    reference_title: "Mutations of the SCO1 gene in mitochondrial cytochrome c oxidase deficiency with neonatal-onset hepatic failure and encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: neonatal-onset hepatic failure and encephalopathy
    explanation: The report describes SCO1 mutations in COX deficiency presenting with neonatal-onset hepatic failure.
- name: Encephalopathy
  description: Encephalopathy, including developmental and epileptic encephalopathy in the expanded spectrum.
  phenotype_term:
    preferred_term: Encephalopathy
    term:
      id: HP:0001298
      label: Encephalopathy
  evidence:
  - reference: PMID:11013136
    reference_title: "Mutations of the SCO1 gene in mitochondrial cytochrome c oxidase deficiency with neonatal-onset hepatic failure and encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: neonatal-onset hepatic failure and encephalopathy
    explanation: Encephalopathy is a core feature of SCO1-related COX deficiency.
- name: Seizures
  description: Epileptic seizures in the developmental and epileptic encephalopathy phenotype.
  phenotype_term:
    preferred_term: Seizures
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:39214134
    reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We describe three patients with MC4DN4 with developmental and epileptic encephalopathy (DEE), hypopituitarism, and SCO1 pathogenic variants.
    explanation: Documents developmental and epileptic encephalopathy in SCO1/MC4DN4.
- name: Hypopituitarism
  description: Progressive hypopituitarism, an expansion of the SCO1/MC4DN4 phenotype.
  phenotype_term:
    preferred_term: Hypopituitarism
    term:
      id: HP:0040075
      label: Hypopituitarism
  evidence:
  - reference: PMID:39214134
    reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We describe three patients with MC4DN4 with developmental and epileptic encephalopathy (DEE), hypopituitarism, and SCO1 pathogenic variants.
    explanation: Documents progressive hypopituitarism in the expanded SCO1/MC4DN4 phenotype.
- name: Lactic acidosis
  description: Elevated lactate from impaired oxidative metabolism.
  phenotype_term:
    preferred_term: Lactic acidosis
    term:
      id: HP:0003128
      label: Lactic acidosis
  evidence:
  - reference: PMID:19682572
    reference_title: "Cytochrome c oxidase deficiency: patients and animal models."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Human diseases associated with COX deficiency including encephalomyopathies, Leigh syndrome, hypertrophic cardiomyopathies, and fatal lactic acidosis are caused by mutations in COX subunits or assembly factors.
    explanation: Lactic acidosis is a recognized manifestation of COX deficiency.
genetic:
- name: SCO1 pathogenic variants causing MC4DN4
  gene_term:
    preferred_term: SCO1
    term:
      id: hgnc:10603
      label: SCO1
  inheritance:
  - name: Autosomal recessive
    evidence:
    - reference: PMID:11013136
      reference_title: "Mutations of the SCO1 gene in mitochondrial cytochrome c oxidase deficiency with neonatal-onset hepatic failure and encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Mutation screening revealed compound heterozygosity for SCO1 gene mutations in the patients.
      explanation: Compound heterozygous SCO1 variants indicate autosomal recessive inheritance.
  features: >
    Biallelic SCO1 variants impair copper delivery to the COX CuA center,
    causing MC4DN4 with hepatic, neurologic, and endocrine involvement.
  evidence:
  - reference: PMID:39214134
    reference_title: "Endocrinological features and epileptic encephalopathy in COX deficiency due to SCO1 mutations: case series and review of literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mitochondrial complex IV deficiency nuclear type 4 (MC4DN4) is a form of COX deficiency associated with pathogenic variants in the SCO1 gene.
    explanation: Identifies SCO1 as the causal gene for MC4DN4.
treatments:
- name: Supportive and Metabolic Care
  description: >
    No curative therapy; supportive management of hepatic failure, seizures,
    endocrine deficits, and lactic acidosis.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care