Traits

Traits linked to TEFM

transcription elongation factor, mitochondrial

The Human Phenotype Ontology links 45 traits to TEFM, 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
Ataxia	Always
CNS demyelination	Always
Degeneration of cerebellum	Always
Delayed speech and language development	Always
Elevated brain lactate level by MRS	Always
Gliosis	Always
Global developmental delay	Always
Thin corpus callosum	Always
Intellectual disability	Very often (80–99%)
Abnormal gait	Often (30–79%)
Grand mal seizures	Often (30–79%)
Epilepsia partialis continua	Sometimes (5–29%)
Exaggerated startle response	Sometimes (5–29%)
Inability to coordinate movements when walking	Sometimes (5–29%)
Jerking	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Visual fixation instability	Always
Visual loss	Always
Weakness of muscles controlling eye movement	Always
Cross-eyed	Often (30–79%)
Drooping upper eyelid	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Optic atrophy	Often (30–79%)
Decreased clarity of vision	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
EMG: decremental response of compound muscle action potential to repetitive nerve stimulation	Always
Appendicular spasticity	Often (30–79%)
Low muscle tone in trunk	Often (30–79%)
Muscle weakness	Often (30–79%)
Ragged-red muscle fibers	Often (30–79%)
Appendicular hypotonia	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Elevated alkaline phosphatase	Always
High urine lactic acid levels	Always
Higher than normal levels of lactate in blood	Always
Hyperprolinemia	Always
Increased blood alanine	Always
Low blood sugar	Always

Abnormality of head or neck

Trait	How often it is seen
Abnormally small head	Always
Eye folds	Often (30–79%)
Low insertion of columella	Often (30–79%)
Prominent nasal bridge	Sometimes (5–29%)

Abnormal cellular phenotype

Trait	How often it is seen
Decreased activity of mitochondrial complex I	Always
Decreased activity of mitochondrial complex IV	Always

Abnormality of the digestive system

Trait	How often it is seen
Vomiting	Always
Feeding difficulties	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Respiratory failure requiring assisted ventilation	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 TEFM and how often each is seen. Find out more at hpo.jax.org.

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