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Start free with EleplanIsolated complex I deficiency
ORPHA:2609Disease
Also called Isolated NADH-CoQ reductase deficiency · Isolated NADH-coenzyme Q reductase deficiency · Isolated NADH-ubiquinone reductase deficiency · Isolated mitochondrial respiratory chain complex I deficiency
What it is
Isolated complex I deficiency is a rare inborn error of metabolism due to mutations in nuclear or mitochondrial genes encoding subunits or assembly factors of the human mitochondrial complex I (NADH: ubiquinone oxidoreductase) and is characterized by a wide range of manifestations including marked and often fatal lactic acidosis, cardiomyopathy, leukoencephalopathy, pure myopathy and hepatopathy with tubulopathy. Among the numerous clinical phenotypes observed are Leigh syndrome, Leber hereditary optic neuropathy and MELAS syndrome.
Key facts
- Age of onset
- All ages
- Inheritance
- Autosomal recessive, Mitochondrial inheritance, X-linked dominant
- Classified as
- Disease
Signs and symptoms
Very common80–99%
31- Abnormal mitochondria in muscle tissue
- Ataxia
- Encephalopathy
- Failure to thrive
- Focal T2 hyperintense brainstem lesion
- Global developmental delay
- Hepatomegaly
- Hypertrophic cardiomyopathy
- Hypoglycemia
- Hypotonia
- Increased circulating pyruvate concentration
- Increased CSF lactate
- Intrauterine growth retardation
- Lactic acidosis
- Lethargy
- Leukodystrophy
- Leukoencephalopathy
- Mitochondrial myopathy
- Muscle weakness
- Nystagmus
- Optic disc pallor
- Optic neuropathy
- Paroxysmal involuntary eye movements
- Poor head control
- Proximal tubulopathy
- Ptosis
- Reduced eye contact
- Respiratory insufficiency
- Sensorineural hearing impairment
- Strabismus
- Vomiting
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Benefit programs to look at
Programs whose eligibility touches the same ICD-10 categories. Eligibility is decided by the administering agency, never by this page.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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