Traits

Traits linked to MT-CO2

mitochondrially encoded cytochrome c oxidase II

The Human Phenotype Ontology links 101 traits to MT-CO2, by body system: features seen in people with one of the gene's rare conditions.

MT-CO2

Abnormality of the nervous system

Trait	How often it is seen
Absent/small cerebral white matter	Very often (80–99%)
Dementia	Very often (80–99%)
Difficulty finding words	Very often (80–99%)
EEG abnormality	Very often (80–99%)
Epilepsy	Very often (80–99%)
Migraine	Very often (80–99%)
Widened cerebral subarachnoid space	Very often (80–99%)
Abnormal gait	Often (30–79%)
Anxiety	Often (30–79%)
Ataxia	Often (30–79%)
Depression	Often (30–79%)
Encephalopathy	Often (30–79%)
Fluctuations in consciousness	Often (30–79%)
Grand mal seizures	Often (30–79%)
Impaired visuospatial constructive cognition	Often (30–79%)
Jerking	Often (30–79%)
Memory impairment	Often (30–79%)
Peripheral neuropathy	Often (30–79%)
Psychosis	Often (30–79%)
Recurrent paroxysmal headache	Often (30–79%)
Seizure affecting one half of brain	Often (30–79%)
Short attention span	Often (30–79%)
Specific learning disability	Often (30–79%)
Weakness of one side of body	Often (30–79%)
Abnormal central motor function	Sometimes (5–29%)
Agenesis of corpus callosum	Sometimes (5–29%)
Bipolar disorder	Sometimes (5–29%)
Brain degeneration	Sometimes (5–29%)
Decrease in size of the outer layer of the brain due to loss of brain cells	Sometimes (5–29%)
Distal peripheral sensory neuropathy	Sometimes (5–29%)
Disturbances of consciousness	Sometimes (5–29%)
Elevated brain lactate level by MRS	Sometimes (5–29%)
Global developmental delay	Sometimes (5–29%)
Mixed demyelinating and axonal polyneuropathy	Sometimes (5–29%)
Motor delay	Sometimes (5–29%)
Nerve damage causing decreased feeling and movement	Sometimes (5–29%)
Peripheral axonal neuropathy	Sometimes (5–29%)
Personality changes	Sometimes (5–29%)
Psychotic mentation	Sometimes (5–29%)
Stuttering	Sometimes (5–29%)
Underdevelopment of part of brain called corpus callosum	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Stroke-like episode	Very often (80–99%)
Cardiac conduction abnormality	Sometimes (5–29%)
Concentric hypertrophic cardiomyopathy	Sometimes (5–29%)
Disease of the heart muscle	Sometimes (5–29%)
Enlarged and thickened heart muscle	Sometimes (5–29%)
Increased blood pressure in blood vessels of lungs	Sometimes (5–29%)
Redness of skin or mucous membrane	Sometimes (5–29%)
Stretched and thinned heart muscle	Sometimes (5–29%)
Wolff-Parkinson-White syndrome	Sometimes (5–29%)
Abnormal heart rate	Not recorded
Abnormal left ventricular function	Not recorded
Cardiac failure	Not recorded
High blood pressure	Not recorded
Left ventricular hypertrophy	Not recorded

Laboratory abnormality

Trait	How often it is seen
Higher than normal levels of lactate in blood	Very often (80–99%)
Increased lactate in body	Very often (80–99%)
Diabetes mellitus	Often (30–79%)
Increased CSF lactate	Often (30–79%)
Increased CSF protein concentration	Often (30–79%)
Fever	Sometimes (5–29%)
High urine protein levels	Sometimes (5–29%)
Noninsulin-dependent diabetes	Sometimes (5–29%)
Type 1 diabetes	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Visual loss	Often (30–79%)
Optic atrophy	Sometimes (5–29%)
Pigmentary retinopathy	Sometimes (5–29%)
Progressive external ophthalmoplegia	Sometimes (5–29%)
Cerebral visual impairment	Not recorded
Clouding of the lens of the eye at birth	Not recorded
Eye muscle paralysis	Not recorded
Hemianopia	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Vomiting	Often (30–79%)
Constipation	Sometimes (5–29%)
Diarrhea	Sometimes (5–29%)
Gastrointestinal dysmotility	Sometimes (5–29%)
Intestinal pseudo-obstruction	Sometimes (5–29%)
Recurring pancreas inflammation	Sometimes (5–29%)
Episodic vomiting	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Muscle weakness	Very often (80–99%)
Ragged-red muscle fibers	Very often (80–99%)
Basal ganglia calcification	Often (30–79%)
Muscle tissue disease	Often (30–79%)
Mitochondrial myopathy	Not recorded

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Often (30–79%)
Bilateral sensorineural hearing impairment	Not recorded
Progressive sensorineural hearing impairment	Not recorded

Abnormality of the endocrine system

Trait	How often it is seen
Decreased parathyroid hormone secretion	Rarely (1–4%)
Hypogonadotropic hypogonadism	Rarely (1–4%)
Underactive thyroid	Rarely (1–4%)

Abnormality of the genitourinary system

Trait	How often it is seen
Focal segmental glomerulosclerosis	Sometimes (5–29%)
Kidney damage	Sometimes (5–29%)
Proximal tubulopathy	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Short stature	Often (30–79%)
Faltering weight	Sometimes (5–29%)
Growth abnormality	Not recorded

Abnormality of the integument

Trait	How often it is seen
Blotchy loss of skin color	Sometimes (5–29%)
Excessive hair growth	Sometimes (5–29%)

Abnormal cellular phenotype

Trait	How often it is seen
Abnormal mitochondria in muscle tissue	Very often (80–99%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Low number of red blood cells or hemoglobin	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Decreased ability to exercise	Sometimes (5–29%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to MT-CO2 and how often each is seen. Find out more at hpo.jax.org.

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