Traits

Traits linked to EXT2

exostosin glycosyltransferase 2

The Human Phenotype Ontology links 136 traits to EXT2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of limbs

Trait	How often it is seen
Abnormal shape of bones of the lower limbs	Often (30–79%)
Abnormality of the knee	Often (30–79%)
Abnormality of the thighbone	Often (30–79%)
Deformed forearm bones	Often (30–79%)
Overlapping toe	Often (30–79%)
Abnormal morphology of ulna	Sometimes (5–29%)
Abnormal shape of hand	Sometimes (5–29%)
Abnormality of the calf bone	Sometimes (5–29%)
Abnormality of the shankbone	Sometimes (5–29%)
Bowing of the long bones	Sometimes (5–29%)
Broad wide portion of long bone	Sometimes (5–29%)
Coxa valga	Sometimes (5–29%)
Deformed radius	Sometimes (5–29%)
Femoroacetabular impingement	Sometimes (5–29%)
Forearm undergrowth	Sometimes (5–29%)
Knock knees	Sometimes (5–29%)
Left and right leg differ in length or width	Sometimes (5–29%)
Limb undergrowth	Sometimes (5–29%)
Limitation of knee mobility	Sometimes (5–29%)
Short lower limbs	Sometimes (5–29%)
Shortened long bone of hand	Sometimes (5–29%)
Abnormal ankle bones	Rarely (1–4%)
Abnormal wrist bones	Rarely (1–4%)
Talipes valgus	Rarely (1–4%)
Coxa vara	Not recorded
Curvature of little finger	Not recorded
Dropped arches	Not recorded
Madelung-like forearm deformities	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Always
Multiple exostoses	Always
Osteochondroma	Always
Scoliosis	Always
Formation of new noncancerous bone on top of existing bone	Very often (80–99%)
Low solidness and mass of the bones	Very often (80–99%)
Abnormal bone structure	Often (30–79%)
Abnormal shape of cartilage	Often (30–79%)
Functional motor deficit	Often (30–79%)
Limitation of joint mobility	Often (30–79%)
Arthritis	Sometimes (5–29%)
Bursitis	Sometimes (5–29%)
Chondrosarcoma	Sometimes (5–29%)
Limited hip movement	Sometimes (5–29%)
Short long bone	Sometimes (5–29%)
Abnormal shape of pelvis bone	Rarely (1–4%)
Bone fracture	Rarely (1–4%)
Neuropathic spinal arthropathy	Rarely (1–4%)
Rib exostoses	Rarely (1–4%)
Scapular exostoses	Rarely (1–4%)
Pelvic bone exostoses	Not recorded
Protuberances at ends of long bones	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Epilepsy	Always
Global developmental delay	Always
IQ between 34 and 49	Always
Delayed speech and language development	Very often (80–99%)
Autism	Often (30–79%)
Intellectual disability, mild	Often (30–79%)
Unsteady walk	Often (30–79%)
Wide based walk	Often (30–79%)
Intellectual disability	Sometimes (5–29%)
Intellectual disability, severe	Sometimes (5–29%)
Loss of ability to walk	Sometimes (5–29%)
Pauses in breathing while sleeping	Sometimes (5–29%)
Somatic sensory dysfunction	Sometimes (5–29%)
Cervical myelopathy	Rarely (1–4%)
Fluid-filled cyst in spinal cord	Rarely (1–4%)
Peripheral nerve compression	Rarely (1–4%)
Pressure on spinal cord	Rarely (1–4%)
Tethered cord	Rarely (1–4%)
Autism spectrum disorder	Not recorded
Motor delay	Not recorded
Poor speech	Not recorded
Repetitive movements	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Big calvaria	Always
Broad head shape	Very often (80–99%)
Broad nasal tip	Very often (80–99%)
Decreased bone formation of skull	Very often (80–99%)
Depressed nasal tip	Very often (80–99%)
Eye folds	Very often (80–99%)
Little lower jaw	Very often (80–99%)
Prominent nasal bridge	Very often (80–99%)
Underdeveloped tissue around nostril	Very often (80–99%)
Bulbous nose	Often (30–79%)
Downturned corners of mouth	Often (30–79%)
Holes in parietal bones	Often (30–79%)
Long philtrum	Often (30–79%)
Short philtrum	Often (30–79%)
Abnormally small head	Sometimes (5–29%)
Flat forehead	Sometimes (5–29%)
High forehead	Sometimes (5–29%)
Prominent forehead	Sometimes (5–29%)
Coarse facial features	Not recorded
Hypoplastic philtrum	Not recorded
Skin tag in front of the ear	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Often (30–79%)
Constipation	Often (30–79%)
Intestinal malrotation	Often (30–79%)
Nausea	Often (30–79%)
Stomach hernia	Sometimes (5–29%)
Stool holding	Sometimes (5–29%)
Volvulus	Sometimes (5–29%)
Intestinal obstruction	Rarely (1–4%)
Poor swallowing	Rarely (1–4%)
Feeding difficulties	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Often (30–79%)
Hole in heart wall separating two lower heart chambers	Often (30–79%)
An opening in the wall separating the top two chambers of the heart	Sometimes (5–29%)
High blood pressure	Sometimes (5–29%)
Patent ductus arteriosus	Rarely (1–4%)
Pseudoaneurysm	Rarely (1–4%)

Abnormality of the genitourinary system

Trait	How often it is seen
Undescended testes	Always
Abnormality of the kidney	Often (30–79%)
Short penis	Often (30–79%)
Nephroblastoma	Sometimes (5–29%)
Urinary retention	Rarely (1–4%)

Constitutional symptom

Trait	How often it is seen
Pain	Often (30–79%)
Muscle ache	Sometimes (5–29%)
Tendon pain	Sometimes (5–29%)
Chest pain	Rarely (1–4%)

Abnormality of the endocrine system

Trait	How often it is seen
Delayed puberty	Sometimes (5–29%)
Early onset of puberty	Sometimes (5–29%)
Underactive thyroid	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Wide-set eyes	Often (30–79%)

Abnormality of the integument

Trait	How often it is seen
Abnormality of the skin	Often (30–79%)
Atypical nail growth	Not recorded
Sparse hair	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Bleeding in brain	Often (30–79%)
Low number of red blood cells or hemoglobin	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Collapsed lung	Rarely (1–4%)
Hemothorax	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Short stature	Often (30–79%)
Uneven or disproportionate growth of one body part compared to another	Sometimes (5–29%)

Abnormality of prenatal development or birth

Trait	How often it is seen
High levels of amniotic fluid	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Abnormality of the outer ear	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
High urine protein levels	Often (30–79%)

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 EXT2 and how often each is seen. Find out more at hpo.jax.org.

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