Traits

Traits linked to TMEM218

transmembrane protein 218

The Human Phenotype Ontology links 47 traits to TMEM218, 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
Global developmental delay	Always
Ataxia	Very often (80–99%)
Cerebellar vermis hypoplasia	Very often (80–99%)
Intellectual disability	Very often (80–99%)
Abnormal gait	Often (30–79%)
Abnormality of neuronal migration	Sometimes (5–29%)
Aplasia/Hypoplasia of the corpus callosum	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Molar tooth sign on MRI	Sometimes (5–29%)
More grooves in brain	Sometimes (5–29%)
Pain insensitivity	Sometimes (5–29%)
Too much cerebrospinal fluid in the brain	Sometimes (5–29%)
Tremor	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Brain tissue sticks out through back of skull	Often (30–79%)
Decreased width of the skull	Often (30–79%)
Long face	Often (30–79%)
Cleft of the mouth	Sometimes (5–29%)
Encephalocele	Sometimes (5–29%)
Highly arched eyebrow	Sometimes (5–29%)
Nasal tip, upturned	Sometimes (5–29%)
Prominent nasal bridge	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Breakdown of light-sensitive cells in back of eye	Always
Oculomotor apraxia	Very often (80–99%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Cat eye	Sometimes (5–29%)
Cross-eyed	Sometimes (5–29%)
Drooping upper eyelid	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Joint contracture of the 5th finger	Often (30–79%)
Duplication of bones of the toes	Sometimes (5–29%)
Extra finger	Sometimes (5–29%)
Postaxial polydactyly	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Abnormal pattern of respiration	Very often (80–99%)
Apnea	Very often (80–99%)
Episodic tachypnea	Very often (80–99%)
Shallow breathing	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Abnormal cardiovascular system morphology	Sometimes (5–29%)
All organs on wrong side of body	Sometimes (5–29%)
Underdeveloped left heart	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Very often (80–99%)
Abnormal vertebral body morphology	Sometimes (5–29%)
Scoliosis	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties in infancy	Often (30–79%)
Enlarged colon lacking nerve cells	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Abnormality of the hypothalamus-pituitary axis	Sometimes (5–29%)

Abnormality of the genitourinary system

Trait	How often it is seen
Polycystic kidney dysplasia	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Overweight	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 TMEM218 and how often each is seen. Find out more at hpo.jax.org.

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