Traits

Traits linked to MT-TT

mitochondrially encoded tRNA-Thr (ACN)

The Human Phenotype Ontology links 38 traits to MT-TT, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Severe global developmental delay	Often (30–79%)
Abnormal autonomic nervous system physiology	Sometimes (5–29%)
Absent reflexes	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Hallucinations	Sometimes (5–29%)
Lethargy	Sometimes (5–29%)
Balance impairment	Not recorded
Dementia	Not recorded
Depression	Not recorded
Difficulty articulating speech	Not recorded
Difficulty sleeping	Not recorded
Dystonia	Not recorded
Lewy bodies	Not recorded
Loss of brain cells	Not recorded
Micrographia	Not recorded
Parkinsonism	Not recorded
Personality changes	Not recorded
Resting tremor	Not recorded
Short stepped shuffling walk	Not recorded
Slow movements	Not recorded
Substantia nigra gliosis	Not recorded
Tremor	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Generalized low muscle tone in neonate	Sometimes (5–29%)
Lethal infantile mitochondrial myopathy	Not recorded
Muscle tissue disease	Not recorded
Rigidity	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Fatal liver failure in infancy	Sometimes (5–29%)
Constipation	Not recorded
Poor swallowing	Not recorded

Abnormality of the genitourinary system

Trait	How often it is seen
Renal failure	Often (30–79%)
Urinary urgency	Not recorded

Laboratory abnormality

Trait	How often it is seen
Severe lactic acidosis	Often (30–79%)
Increased lactate in body	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Expressionless face	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Disease of the heart muscle	Often (30–79%)

Abnormality of the eye

Trait	How often it is seen
Progressive external ophthalmoplegia	Often (30–79%)

Abnormality of the respiratory system

Trait	How often it is seen
Neonatal respiratory distress	Sometimes (5–29%)

Abnormality of the voice

Trait	How often it is seen
Weak voice	Not recorded

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

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