Traits

Traits linked to EXT1

exostosin glycosyltransferase 1

The Human Phenotype Ontology links 97 traits to EXT1, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of limbs

Trait	How often it is seen
Cone-shaped end part of finger bones	Very often (80–99%)
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%)
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%)
Avascular necrosis of the capital femoral epiphysis	Sometimes (5–29%)
Bilateral single transverse palmar creases	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 fingers or toes	Sometimes (5–29%)
Short lower limbs	Sometimes (5–29%)
Shortened long bone of hand	Sometimes (5–29%)
Talipes	Sometimes (5–29%)
Abnormal ankle bones	Rarely (1–4%)
Abnormal wrist bones	Rarely (1–4%)
Talipes valgus	Rarely (1–4%)
Coxa vara	Not recorded
Madelung-like forearm deformities	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Multiple exostoses	Always
Osteochondroma	Always
Bone pain	Very often (80–99%)
Delayed bone maturation	Very often (80–99%)
Formation of new noncancerous bone on top of existing bone	Very often (80–99%)
Multiple long-bone exostoses	Very often (80–99%)
Abnormal bone structure	Often (30–79%)
Abnormal shape of cartilage	Often (30–79%)
Double-Jointed	Often (30–79%)
Functional motor deficit	Often (30–79%)
Joint dislocation	Often (30–79%)
Limitation of joint mobility	Often (30–79%)
Abnormal formation of the hip	Sometimes (5–29%)
Arthritis	Sometimes (5–29%)
Bursitis	Sometimes (5–29%)
Chondrosarcoma	Sometimes (5–29%)
Limited hip movement	Sometimes (5–29%)
Low muscle tone	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 head or neck

Trait	How often it is seen
Bulbous nose	Very often (80–99%)
Deep philtrum	Very often (80–99%)
Long philtrum	Very often (80–99%)
Sparse scalp hair	Very often (80–99%)
Thin red part of the upper lip	Very often (80–99%)
Aplasia/Hypoplasia of the mandible	Often (30–79%)
Thick eyebrow	Often (30–79%)
Abnormal dentition	Sometimes (5–29%)
Abnormality of the palate	Sometimes (5–29%)
Abnormally small head	Sometimes (5–29%)
Extra teeth	Sometimes (5–29%)
Thick nasal alae	Sometimes (5–29%)
Wide nasal bridge	Sometimes (5–29%)

Abnormality of the nervous system

Trait	How often it is seen
Intellectual disability	Often (30–79%)
Somatic sensory dysfunction	Sometimes (5–29%)
Ventriculomegaly	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%)

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 ear

Trait	How often it is seen
Ears rotated toward back of head	Very often (80–99%)
Prominent ear	Very often (80–99%)
Conductive deafness	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Frequent urinary tract infections	Sometimes (5–29%)
Vesicoureteral reflux	Sometimes (5–29%)
Urinary retention	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Short stature	Very often (80–99%)
Growth delay	Sometimes (5–29%)
Uneven or disproportionate growth of one body part compared to another	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Sometimes (5–29%)
Pseudoaneurysm	Rarely (1–4%)

Abnormality of the digestive system

Trait	How often it is seen
Intestinal obstruction	Rarely (1–4%)
Poor swallowing	Rarely (1–4%)

Abnormality of the respiratory system

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

Abnormality of the integument

Trait	How often it is seen
Loose redundant skin	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 EXT1 and how often each is seen. Find out more at hpo.jax.org.

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