Traits

Traits linked to MT-TL2

mitochondrially encoded tRNA-Leu (CUN) 2

The Human Phenotype Ontology links 104 traits to MT-TL2, by body system: features seen in people with one of the gene's rare conditions.

MT-TL2

Abnormality of the nervous system

Trait	How often it is seen
Episodic hemiplegia	Very often (80–99%)
Abnormal autonomic nervous system physiology	Often (30–79%)
Ataxia	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Brisk reflexes	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Dystonia	Often (30–79%)
Epilepsy	Often (30–79%)
Intellectual disability	Often (30–79%)
Neurodevelopmental delay	Often (30–79%)
Tetraparesis	Often (30–79%)
Abnormal pyramidal sign	Sometimes (5–29%)
Absent reflexes	Sometimes (5–29%)
Aggressive behavior	Sometimes (5–29%)
Bulbar signs	Sometimes (5–29%)
Can't control feelings	Sometimes (5–29%)
Chorea	Sometimes (5–29%)
Choreoathetosis	Sometimes (5–29%)
Depression	Sometimes (5–29%)
Difficulty articulating speech	Sometimes (5–29%)
Focal motor seizure	Sometimes (5–29%)
Grand mal seizures	Sometimes (5–29%)
Headache	Sometimes (5–29%)
Impulsivity	Sometimes (5–29%)
Increased reflexes	Sometimes (5–29%)
Intellectual disability, mild	Sometimes (5–29%)
Paroxysmal dyskinesia	Sometimes (5–29%)
Repeated seizures without recovery between them	Sometimes (5–29%)
Tremor	Sometimes (5–29%)
Worsening neurological symptoms	Sometimes (5–29%)
Brain imaging abnormality	Not recorded
Dementia	Not recorded
EEG abnormality	Not recorded
Encephalopathy	Not recorded
Migraine	Not recorded
Weakness of one side of body	Not recorded

Abnormality of the eye

Trait	How often it is seen
Progressive external ophthalmoplegia	Very often (80–99%)
Abnormal involuntary eye movements	Often (30–79%)
Dilated pupil	Often (30–79%)
Drooping upper eyelid	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Inward turning cross eyed	Often (30–79%)
Outward facing eye ball	Often (30–79%)
Ocular flutter	Sometimes (5–29%)
Oculomotor apraxia	Sometimes (5–29%)
Cerebral visual impairment	Not recorded
Clouding of the lens of the eye at birth	Not recorded
Double vision	Not recorded
Eye muscle paralysis	Not recorded
Hemianopia	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal T-wave	Sometimes (5–29%)
Cardiac conduction abnormality	Sometimes (5–29%)
Abnormal heart rate	Rarely (1–4%)
Disease of the heart muscle	Rarely (1–4%)
Abnormal left ventricular function	Not recorded
Cardiac failure	Not recorded
High blood pressure	Not recorded
Left ventricular hypertrophy	Not recorded
Stroke-like episode	Not recorded
Wolff-Parkinson-White syndrome	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Abnormality of the gastrointestinal tract	Very often (80–99%)
Gastrointestinal dysmotility	Very often (80–99%)
Abdominal bloating	Often (30–79%)
Anorexia	Often (30–79%)
Constipation	Often (30–79%)
Diarrhea	Often (30–79%)
Oral-pharyngeal dysphagia	Often (30–79%)
Poor swallowing	Often (30–79%)
Vomiting	Often (30–79%)
Episodic vomiting	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Muscle abnormality related to mitochondrial dysfunction	Very often (80–99%)
Axial muscle weakness	Often (30–79%)
Decreased lung function due to weak breathing muscles	Often (30–79%)
EMG abnormality	Often (30–79%)
Progressive proximal muscle weakness	Often (30–79%)
Ragged-red muscle fibers	Often (30–79%)
Low muscle tone	Sometimes (5–29%)
Rigidity	Sometimes (5–29%)
Mitochondrial myopathy	Not recorded
Muscle tissue disease	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Decreased facial muscle tone	Sometimes (5–29%)
Downturned corners of mouth	Sometimes (5–29%)
Exaggerated cupid's bow	Sometimes (5–29%)
High forehead	Sometimes (5–29%)
Thin eyebrow	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Higher than normal levels of lactate in blood	Often (30–79%)
Mildly elevated creatine kinase	Often (30–79%)
Dehydration	Sometimes (5–29%)
Diabetes mellitus	Not recorded
Increased lactate in body	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Stiff lung or chest wall causing decreased lung volume	Often (30–79%)
Apnea	Sometimes (5–29%)
Aspiration	Sometimes (5–29%)
Breathing difficulties	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Flushing	Often (30–79%)
Paleness	Often (30–79%)
Excessive sweating	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Bilateral sensorineural hearing impairment	Not recorded
Progressive sensorineural hearing impairment	Not recorded

Growth abnormality

Trait	How often it is seen
Faltering weight	Often (30–79%)
Growth abnormality	Not recorded

Abnormal cellular phenotype

Trait	How often it is seen
Abnormal mitochondria in muscle tissue	Often (30–79%)

Abnormality of limbs

Trait	How often it is seen
Skewfoot	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Underactive thyroid	Often (30–79%)

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-TL2 and how often each is seen. Find out more at hpo.jax.org.

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