Traits

Traits linked to COL1A2

collagen type I alpha 2 chain

The Human Phenotype Ontology links 135 traits to COL1A2, by body system: features seen in people with one of the gene's rare conditions.

COL1A2

Abnormality of the musculoskeletal system

Trait	How often it is seen
Bell-shaped thorax	Always
Crumpled long bones	Always
Double-Jointed	Always
Multiple fractures present at birth	Always
Multiple rib fractures	Always
Small chest	Always
Thin ribs	Always
Abnormal formation of the hip	Very often (80–99%)
Hypermobility of all joints	Very often (80–99%)
Multiple joint dislocation	Very often (80–99%)
Recurrent fractures	Very often (80–99%)
Funnel chest	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Hernia	Often (30–79%)
Increased mobility of outermost hinge joint	Often (30–79%)
Increased susceptibility to fractures	Often (30–79%)
Joint dislocation	Often (30–79%)
Low muscle tone	Often (30–79%)
Popcorn calcification	Often (30–79%)
Scoliosis	Often (30–79%)
Kyphoscoliosis	Sometimes (5–29%)
Multiple shoulder dislocation	Sometimes (5–29%)
Osteopenia	Sometimes (5–29%)
Tendon rupture	Sometimes (5–29%)
Tendon thickening	Sometimes (5–29%)
Thoracolumbar scoliosis	Sometimes (5–29%)
Abnormal shape of pelvic girdle bone	Not recorded
Biconcave flattened vertebrae	Not recorded
Biconcave vertebral bodies	Not recorded
Bowing of limbs due to multiple fractures	Not recorded
Broad long bones	Not recorded
Flattened vertebrae	Not recorded
Hunched back	Not recorded
Joint subluxation	Not recorded
Low solidness and mass of the bones	Not recorded
Osteoporosis	Not recorded
Prominent swayback	Not recorded
Severe generalized osteoporosis	Not recorded
Slender long bone	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Absent bone maturation of skullcap	Always
Dental crowding	Often (30–79%)
Depressed nasal bridge	Often (30–79%)
Eye folds	Often (30–79%)
Frontal bossing	Often (30–79%)
Little lower jaw	Often (30–79%)
Receding chin	Often (30–79%)
Wide fontanelles	Often (30–79%)
Bulbous nose	Sometimes (5–29%)
Cleft lip	Sometimes (5–29%)
Cleft palate	Sometimes (5–29%)
Dentinogenesis imperfecta	Sometimes (5–29%)
Extra bones within cranial sutures	Sometimes (5–29%)
High palate	Sometimes (5–29%)
Midface retrusion	Sometimes (5–29%)
Thick eyebrow	Sometimes (5–29%)
Basilar impression	Not recorded
Beaked nose	Not recorded
Flattening of the skull base	Not recorded
Soft skullcap	Not recorded
Triangular face	Not recorded
Wider-than-typical soft spot of skull	Not recorded

Abnormality of limbs

Trait	How often it is seen
Hip dislocation	Always
Limb undergrowth	Always
Avascular necrosis of the capital femoral epiphysis	Very often (80–99%)
Congenital bilateral hip dislocation	Very often (80–99%)
Abnormal feet structure	Often (30–79%)
Absent phalangeal crease	Often (30–79%)
Back knee	Often (30–79%)
Bunion	Often (30–79%)
Dropped arches	Often (30–79%)
Knock knees	Often (30–79%)
Long fingers	Often (30–79%)
Talipes	Often (30–79%)
Foot and ankle bend up toward shin of leg	Sometimes (5–29%)
Gap between 1st and 2nd toes	Sometimes (5–29%)
Swan neck-like deformities of the fingers	Sometimes (5–29%)
Club feet	Rarely (1–4%)
Abnormally indented hip sockets	Not recorded
Bowed shankbone	Not recorded
Bowing of thighbone at birth, straightening with time	Not recorded
Finger joint hyperextensibility	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal heart valve morphology	Very often (80–99%)
Mitral regurgitation	Very often (80–99%)
Aortic regurgitation	Often (30–79%)
Bulge in wall of root of large artery that carries blood away from heart	Often (30–79%)
Tricuspid regurgitation	Often (30–79%)
An opening in the wall separating the top two chambers of the heart	Sometimes (5–29%)
Arterial rupture	Sometimes (5–29%)
Left ventricular hypertrophy	Sometimes (5–29%)
Mitral valve prolapse	Sometimes (5–29%)
Pulmonic regurgitation	Sometimes (5–29%)
Cardiac failure	Not recorded
Increased blood pressure in blood vessels of lungs	Not recorded

Abnormality of the integument

Trait	How often it is seen
Dermal translucency	Always
Hyperelastic skin	Always
Thin skin	Very often (80–99%)
Fragile skin	Often (30–79%)
Poor wound healing	Often (30–79%)
Soft skin	Often (30–79%)
Soft, doughy skin	Often (30–79%)
Sunken or indented skin due to damage	Often (30–79%)

Abnormality of the eye

Trait	How often it is seen
Blue outer white part of eyeball	Always
Close sighted	Often (30–79%)
Cross-eyed	Often (30–79%)
Drooping upper eyelid	Often (30–79%)
Wide-set eyes	Often (30–79%)
Myopic astigmatism	Sometimes (5–29%)

Abnormality of the nervous system

Trait	How often it is seen
Delayed ability to walk	Very often (80–99%)
Motor delay	Very often (80–99%)
Epilepsy	Sometimes (5–29%)
Global developmental delay	Sometimes (5–29%)
IQ between 34 and 49	Sometimes (5–29%)
Delayed motor skills	Not recorded

Abnormality of prenatal development or birth

Trait	How often it is seen
Feet or buttocks of fetus positioned near opening of uterus	Sometimes (5–29%)
High levels of amniotic fluid	Sometimes (5–29%)
Less than 10 fetal movements in 12 hours	Sometimes (5–29%)
Premature rupture of membranes	Sometimes (5–29%)
Premature birth	Not recorded

Growth abnormality

Trait	How often it is seen
Short stature	Often (30–79%)
Disproportionate tall stature	Sometimes (5–29%)
Disproportionate short-limb short stature	Not recorded
Neonatal short-limb short stature	Not recorded
Small for gestational age	Not recorded

Abnormality of the ear

Trait	How often it is seen
Severe conductive hearing impairment	Sometimes (5–29%)
Hearing impairment	Not recorded
Otosclerosis	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Inguinal hernia	Often (30–79%)
Femoral hernia	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Breathing difficulty	Sometimes (5–29%)
Respiratory function loss	Not recorded

Constitutional symptom

Trait	How often it is seen
Joint pain	Often (30–79%)
Fatigue	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Bruising susceptibility	Always

Abnormality of the genitourinary system

Trait	How often it is seen
Bladder diverticulum	Rarely (1–4%)

Laboratory abnormality

Trait	How often it is seen
Nonimmune hydrops fetalis	Not recorded

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 COL1A2 and how often each is seen. Find out more at hpo.jax.org.

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