Traits

Traits linked to SYT1

synaptotagmin 1

The Human Phenotype Ontology links 70 traits to SYT1, 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 ability to walk	Always
Absent speech development	Very often (80–99%)
Autism spectrum disorder	Very often (80–99%)
EEG abnormality	Very often (80–99%)
Motor delay	Very often (80–99%)
Self-injurious behavior	Very often (80–99%)
Severe global developmental delay	Very often (80–99%)
Difficulty sleeping	Often (30–79%)
Hyperactive movements	Often (30–79%)
Intellectual disability	Often (30–79%)
Poor eye contact	Often (30–79%)
Repetitive compulsive behavior	Often (30–79%)
Repetitive movements	Often (30–79%)
Agitation	Sometimes (5–29%)
Anxiety	Sometimes (5–29%)
Ataxia	Sometimes (5–29%)
Athetoid cerebral palsy	Sometimes (5–29%)
Chorea	Sometimes (5–29%)
Choreoathetosis	Sometimes (5–29%)
Delayed myelination	Sometimes (5–29%)
Dystonia	Sometimes (5–29%)
EEG with focal sharp waves	Sometimes (5–29%)
EEG with series of focal spikes	Sometimes (5–29%)
EEG with spike-wave complexes	Sometimes (5–29%)
Hemiballismus	Sometimes (5–29%)
Pauses in breathing while sleeping	Sometimes (5–29%)
Poor speech	Sometimes (5–29%)
Self-biting	Sometimes (5–29%)
Self-mutilation	Sometimes (5–29%)
Disorder of involuntary muscle movements	Not recorded
Global developmental delay	Not recorded
Inability to walk	Not recorded
Involuntary movements	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Abnormal location of the eyebrow	Sometimes (5–29%)
Almond shaped eyes	Sometimes (5–29%)
Eye folds	Sometimes (5–29%)
High, prominent forehead	Sometimes (5–29%)
Horizontal eyebrow	Sometimes (5–29%)
Prominent nasal tip	Sometimes (5–29%)
Short nose	Sometimes (5–29%)
Smooth philtrum	Sometimes (5–29%)
Thin red part of the upper lip	Sometimes (5–29%)
Widow's peak	Sometimes (5–29%)
High forehead	Not recorded

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Inward turning cross eyed	Often (30–79%)
Poor visual behavior for age	Often (30–79%)
Farsightedness	Sometimes (5–29%)
Visual impairment	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Decreased muscle tone in infant	Very often (80–99%)
Double-Jointed	Sometimes (5–29%)
Excessive inward curvature of lower spine	Sometimes (5–29%)
Progressive flexion contractures	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)
Low muscle tone, in neonatal onset	Not recorded

Abnormality of limbs

Trait	How often it is seen
Club foot on both sides	Sometimes (5–29%)
Equinus calcaneus	Sometimes (5–29%)
Pes valgus	Sometimes (5–29%)
Webbed 2nd and 3rd toes	Sometimes (5–29%)
Abnormal feet structure	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Central apnea	Sometimes (5–29%)
Intermittent overbreathing	Sometimes (5–29%)
Rapid breathing	Sometimes (5–29%)
Softening of voice box tissue	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Often (30–79%)
Vomiting	Often (30–79%)
Feeding difficulties	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
An opening in the wall separating the top two chambers of the heart	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Dermoid cyst	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 SYT1 and how often each is seen. Find out more at hpo.jax.org.

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