Traits

Traits linked to STT3A

STT3 oligosaccharyltransferase complex catalytic subunit A

The Human Phenotype Ontology links 36 traits to STT3A, 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
Degeneration of cerebellum	Always
Epilepsy	Always
Global developmental delay	Always
Intellectual disability	Always
Cavum septum pellucidum	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Motor delay	Often (30–79%)
Aggressive behavior	Sometimes (5–29%)
Fluid-filled sac located in membrane surrounding brain or spinal cord	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Abnormally small head	Always
Big lower jaw	Often (30–79%)
High frontal hairline	Often (30–79%)
Short opening between the eyelids	Often (30–79%)
Thin red part of the upper lip	Often (30–79%)
Wide nasal bridge	Often (30–79%)
Big calvaria	Sometimes (5–29%)
Long face	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Generalized decreased muscle tone	Always
Low muscle tone	Always
Muscle spasm	Often (30–79%)
Spasticity and rigidity of muscles	Often (30–79%)
Degenerative joint disease	Sometimes (5–29%)
Increased skeletal muscle cells	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Short penis	Often (30–79%)
Smaller than typical growth of scrotum	Often (30–79%)
Undescended testes	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Always
Prenatal growth deficiency	Sometimes (5–29%)
Short stature	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Impaired smooth pursuit	Often (30–79%)
Cross-eyed	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Subdural hemorrhage	Sometimes (5–29%)

Abnormality of the breast

Trait	How often it is seen
Inverted nipples	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties	Always

Abnormality of the ear

Trait	How often it is seen
Long ear	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Abnormal glycosylation	Always

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 STT3A and how often each is seen. Find out more at hpo.jax.org.

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