Traits

Traits linked to GPAA1

glycosylphosphatidylinositol anchor attachment 1

The Human Phenotype Ontology links 39 traits to GPAA1, 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
Degeneration of cerebellum	Always
Delayed speech and language development	Always
Difficulty articulating speech	Always
Global developmental delay	Always
Inability to coordinate movements when walking	Always
Lack of coordination of movement	Always
EEG abnormality	Very often (80–99%)
Epilepsy	Very often (80–99%)
Abnormal gait	Often (30–79%)
Grand mal seizures	Often (30–79%)
Increased reflexes	Often (30–79%)
Intellectual disability, mild	Often (30–79%)
Myoclonic seizure	Often (30–79%)
Neurodevelopmental delay	Often (30–79%)
Small cerebellum	Often (30–79%)
Tremor	Often (30–79%)
Apraxia	Sometimes (5–29%)
Brief seizures with staring spells	Sometimes (5–29%)
Sudden loss of muscle tone	Sometimes (5–29%)
Repeated seizures without recovery between them	Rarely (1–4%)
Inability to walk	Not recorded
Intellectual disability	Not recorded

Abnormality of the eye

Trait	How often it is seen
Involuntary, rapid, rhythmic eye movements	Very often (80–99%)
Close sighted	Often (30–79%)
Oculomotor apraxia	Often (30–79%)
Wide-set eyes	Often (30–79%)
Optic atrophy	Sometimes (5–29%)
Visual impairment	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Always
Osteopenia	Always
Difficulty in standing	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Often (30–79%)
Osteoporosis	Often (30–79%)

Abnormality of head or neck

Trait	How often it is seen
Broad nasal tip	Often (30–79%)
Narrow forehead	Often (30–79%)
Nasal tip, upturned	Often (30–79%)
Prominent forehead	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
Elevated alkaline phosphatase	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 GPAA1 and how often each is seen. Find out more at hpo.jax.org.

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