Traits

Traits linked to TMTC3

transmembrane O-mannosyltransferase targeting cadherins 3

The Human Phenotype Ontology links 51 traits to TMTC3, 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
Delayed fine motor development	Always
Delayed motor skills	Always
Delayed social development	Always
Delayed speech and language development	Always
Global developmental delay	Always
Intellectual disability	Always
Abnormal cerebral white matter morphology	Often (30–79%)
Abnormal myelination	Often (30–79%)
Abnormal shape of nervous system	Often (30–79%)
Agyria	Often (30–79%)
Autism spectrum disorder	Often (30–79%)
Dysgyria	Often (30–79%)
Epilepsy	Often (30–79%)
Gray matter heterotopia	Often (30–79%)
Periventricular heterotopia	Often (30–79%)
Seizure affecting one half of brain	Often (30–79%)
Severe global developmental delay	Often (30–79%)
Small brainstem	Often (30–79%)
Small cerebellum	Often (30–79%)
Too much cerebrospinal fluid in the brain	Often (30–79%)
Type II lissencephaly	Often (30–79%)
Underdevelopment of part of brain called corpus callosum	Often (30–79%)
Ventriculomegaly	Often (30–79%)
Absent speech development	Sometimes (5–29%)
Cerebral hypomyelination	Sometimes (5–29%)
More grooves in brain	Sometimes (5–29%)
Retrocerebellar cyst	Sometimes (5–29%)
Delayed ability to walk	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Appendicular spasticity	Always
Low muscle tone in trunk	Always
Hernia	Very often (80–99%)
Scoliosis	Very often (80–99%)
Double-Jointed	Often (30–79%)
Shoulder dislocation	Sometimes (5–29%)
EMG abnormality	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal heart valve morphology	Often (30–79%)
Aortic regurgitation	Often (30–79%)
Patent ductus arteriosus	Often (30–79%)
Bulge in wall of large artery that carries blood away from heart	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Optic atrophy	Often (30–79%)
Abnormally small eyeball	Sometimes (5–29%)
Clouding of the lens of the eye	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Brain tissue sticks out through back of skull	Often (30–79%)
Abnormally small head	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Club feet	Often (30–79%)
Dislocated kneecap	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Very often (80–99%)
Pyloric stenosis	Very often (80–99%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Bleeding tendency	Very often (80–99%)

Abnormality of the integument

Trait	How often it is seen
Thin skin	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
Elevated blood creatine phosphokinase	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 TMTC3 and how often each is seen. Find out more at hpo.jax.org.

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