Traits

Traits linked to COL18A1

collagen type XVIII alpha 1 chain

The Human Phenotype Ontology links 71 traits to COL18A1, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the eye

Trait	How often it is seen
Chorioretinal atrophy	Always
Gaze-evoked nystagmus	Always
Glaucoma	Always
Macular hypoplasia	Always
Peripapillary atrophy	Always
Visual impairment	Always
Close sighted	Very often (80–99%)
Macular degeneration	Very often (80–99%)
Retinal detachment	Very often (80–99%)
Severe near sightedness	Very often (80–99%)
Vitreoretinopathy	Very often (80–99%)
Abnormal vitreous humor morphology	Often (30–79%)
Band keratopathy	Often (30–79%)
Clouding of the lens of the eye at birth	Often (30–79%)
Cortical cataract	Often (30–79%)
High eye pressure	Often (30–79%)
Horizontal nystagmus	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Iris transillumination defect	Often (30–79%)
Optic disc pallor	Often (30–79%)
Partially dislocated lens	Often (30–79%)
Progressive loss of vision	Often (30–79%)
Visual loss	Often (30–79%)
Angle closure glaucoma	Sometimes (5–29%)
Clouding of the lens of the eye	Sometimes (5–29%)
Cross-eyed	Sometimes (5–29%)
Ectopia lentis	Sometimes (5–29%)
Persistent pupillary membrane	Sometimes (5–29%)
Anterior synechiae of the anterior chamber	Not recorded
Increased cup-to-disc ratio	Not recorded
Partial loss of field of vision	Not recorded
Phthisis bulbi	Not recorded
Slow pupillary light response	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Abnormally small head	Always
Bulbous nose	Always
Horizontal eyebrow	Always
Narrow face	Always
Narrow forehead	Always
Prominent forehead	Always
Brain tissue sticks out through back of skull	Very often (80–99%)
Cranial defect	Very often (80–99%)
Absence of scalp hair	Sometimes (5–29%)
Depressed nasal bridge	Sometimes (5–29%)
Eye folds	Sometimes (5–29%)
Midface retrusion	Sometimes (5–29%)
Corners of eye widely separated	Rarely (1–4%)

Abnormality of the nervous system

Trait	How often it is seen
Absent septum pellucidum	Always
Ataxia	Always
Degeneration of cerebellum	Always
Degeneration of cerebrum	Always
Intellectual disability	Always
Myoclonic seizure	Always
Occipital meningocele	Always
More grooves in brain	Often (30–79%)
Too much cerebrospinal fluid in the brain	Often (30–79%)
Ventriculomegaly	Often (30–79%)
Epilepsy	Sometimes (5–29%)
Global developmental delay	Sometimes (5–29%)
Spina bifida occulta	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Narrowing of blood vessels in back of eye	Very often (80–99%)
Heart tip and four chambers point towards right side of body	Sometimes (5–29%)
Lymphangioma	Sometimes (5–29%)
Patent ductus arteriosus	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Bifid ureter	Sometimes (5–29%)
Hydronephrosis	Sometimes (5–29%)
Vesicoureteral reflux	Sometimes (5–29%)
Duplicated collecting system	Rarely (1–4%)

Abnormality of the digestive system

Trait	How often it is seen
Extra kidney	Sometimes (5–29%)
Pyloric stenosis	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Abnormality of the hair	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Double-Jointed	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 COL18A1 and how often each is seen. Find out more at hpo.jax.org.

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