RecruitingNCT01694940
Mitochondrial
Mitochondrial Complex IV Deficiency
Also known as cytochrome c oxidase deficiency, COX deficiency, complex IV deficiency
Mitochondrial complex IV deficiency is caused by mutations in genes encoding cytochrome c oxidase (COX) subunits or assembly factors, impairing electron transfer from cytochrome c to molecular oxygen and thereby reducing ATP synthesis. SURF
ORPHA:254905 ↗Gene SURF1Gene SCO1Gene SCO2Gene COX10Prevalence Second most common mitochondrial respiratory chain disorder; approximately 1 in 100,000–200,000Onset Neonatal to childhood
2
studies recruiting now
as of 7 Sept 2026
3
studies registered in total
as of 7 Sept 2026
3
countries with a recruiting site
as of 7 Sept 2026
15 Feb 2013
most recent study posted
among recruiting studies
Recruiting trials
RecruitingNCT01793168
Rare Disease Patient Registry & Natural History Study - Coordination of Rare Diseases at Sanford
Showing the 2 most recently updated recruiting studies, as recorded 7 Sept 2026. Live status on each study page.
Search all Mitochondrial Complex IV Deficiency studiesWhere recruiting studies are running
Countries with at least one recruiting site among the studies above, 7 Sept 2026. Tap a country to search trials there.
Keep watching
Get an email when a new Mitochondrial Complex IV Deficiency study opens.
One email a day at most. Unsubscribe with one click.
Used only for these alerts. Privacy.
Support
Patient organisations
Registry: North American Mitochondrial Disease Consortium (NAMDC) Registry · Join ↗. Registries connect patients to researchers and often hear about trials first.
About Mitochondrial Complex IV Deficiency
Mitochondrial complex IV deficiency is caused by mutations in genes encoding cytochrome c oxidase (COX) subunits or assembly factors, impairing electron transfer from cytochrome c to molecular oxygen and thereby reducing ATP synthesis. SURF1 mutations are the most common nuclear cause and are strongly associated with Leigh syndrome, while SCO2 mutations typically present with fatal infantile cardioencephalomyopathy. Clinical presentations are broad, reflecting both genotype and residual enzyme activity levels.
Common clinical features
Leigh syndrome features (SURF1-related)Hypertrophic cardiomyopathy (SCO2-related)Neonatal hypotonia and respiratory failureLactic acidosisLiver failure (neonatal hepatopathy)Encephalopathy and developmental regressionProximal myopathy and exercise intolerance
From Orphanet’s phenotype annotations (CC BY 4.0). Not a complete list.
Before you apply
Things trial teams commonly ask about for Mitochondrial Complex IV Deficiency. Not eligibility rules; those are set by each study.
- Tissue-specific COX enzyme activity assay (in muscle or liver) is required for biochemical diagnosis; specify the tissue analysed when applying, as activity levels vary between tissues.
- SURF1 mutation status is a common stratification variable given its strong Leigh syndrome association; ensure full sequencing of the SURF1 gene is performed.
- Cardiac assessment including echocardiography is often a prerequisite given the risk of cardiomyopathy, particularly in SCO2-related disease; have recent cardiac imaging available.
Related conditions
Information, not medical advice. Trial listings are shown as recorded on ClinicalTrials.gov; whether any study is right for you is a decision for you and your clinicians, and eligibility is decided by each research team. Disease information from Orphanet (CC BY 4.0).