Traits

Traits linked to GRM1

glutamate metabotropic receptor 1

The Human Phenotype Ontology links 41 traits to GRM1, 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
Absent speech development	Always
Ataxia	Always
Degeneration of cerebellum	Always
Delayed speech and language development	Always
Difficulty articulating speech	Always
Difficulty performing quick and alternating movements	Always
Global developmental delay	Always
Inability to coordinate movements when walking	Always
Inability to walk	Always
Intellectual disability	Always
Lack of coordination of movement	Always
Severe global developmental delay	Always
Tremor	Always
Increased reflexes	Very often (80–99%)
Abnormal speech pattern	Often (30–79%)
Dilated fourth ventricle	Often (30–79%)
Inferior cerebellar vermis hypoplasia	Often (30–79%)
Retrocerebellar cyst	Often (30–79%)
Uncoordinated limb movement	Often (30–79%)
Brisk reflexes	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Motor delay	Sometimes (5–29%)
Peripheral nerve disease	Sometimes (5–29%)
Abnormal pyramidal sign	Not recorded

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Always
Gaze-evoked nystagmus	Always
Hypermetric saccades	Always
Abnormality of ocular abduction	Often (30–79%)
Drooping upper eyelid	Often (30–79%)
Gaze-evoked horizontal nystagmus	Often (30–79%)
Hypometric saccades	Often (30–79%)
Inward turning cross eyed	Often (30–79%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone in trunk	Always
Difficulty in standing	Very often (80–99%)
Frequent falls	Often (30–79%)
Functional motor deficit	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Poor swallowing	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Ringing in ears	Often (30–79%)

Constitutional symptom

Trait	How often it is seen
Fatigue	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Short stature	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 GRM1 and how often each is seen. Find out more at hpo.jax.org.

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