Traits

Traits linked to TBR1

T-box brain transcription factor 1

The Human Phenotype Ontology links 38 traits to TBR1, 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
Intellectual disability, severe	Always
Behavioral abnormality	Very often (80–99%)
Epilepsy	Very often (80–99%)
Global developmental delay	Very often (80–99%)
Intellectual disability	Very often (80–99%)
Severe global developmental delay	Very often (80–99%)
Autism spectrum disorder	Often (30–79%)
Fewer and broader ridges in brain	Rarely (1–4%)
Autism	Not recorded
Delayed ability to walk	Not recorded
Delayed speech and language development	Not recorded
Inability to walk	Not recorded
Poor social interactions	Not recorded
Repetitive movements	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Cleft palate	Very often (80–99%)
Downward slanting of the opening between the eyelids	Very often (80–99%)
Short neck	Very often (80–99%)
Abnormal oral frenulum morphology	Often (30–79%)
Short philtrum	Often (30–79%)
Small face	Often (30–79%)

Abnormality of limbs

Trait	How often it is seen
Bullet-shaped outermost bone of big toe	Very often (80–99%)
Fused toes	Very often (80–99%)
Hand clenching	Very often (80–99%)
Long fingers	Very often (80–99%)
Permanent flexion of the finger	Very often (80–99%)

Abnormality of the eye

Trait	How often it is seen
Abnormality of the iris	Very often (80–99%)
Abnormally small eyeball	Often (30–79%)
Clouding of the lens of the eye	Often (30–79%)
Notched pupil	Often (30–79%)
Wide-set eyes	Often (30–79%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone, in neonatal onset	Very often (80–99%)
Double-Jointed	Rarely (1–4%)
Generalized decreased muscle tone	Not recorded

Growth abnormality

Trait	How often it is seen
Faltering weight	Very often (80–99%)
Growth delay	Very often (80–99%)
Small for gestational age	Very often (80–99%)

Abnormality of the ear

Trait	How often it is seen
Ears rotated toward back of head	Very often (80–99%)

Abnormality of the respiratory system

Trait	How often it is seen
Central apnea	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 TBR1 and how often each is seen. Find out more at hpo.jax.org.

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