Traits

Traits linked to HTT

huntingtin

The Human Phenotype Ontology links 90 traits to HTT, 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
Abnormal pyramidal sign	Always
Agitation	Always
Caudate atrophy	Always
Cerebellar vermis atrophy	Always
Degeneration of cerebrum	Always
Difficulty sleeping	Always
Dystonia	Always
Focal impaired awareness seizure	Always
Global developmental delay	Always
Intellectual disability, severe	Always
Loss of developmental milestones	Always
Repetitive movements	Always
Slow movements	Always
Tremor	Always
Chorea	Very often (80–99%)
Increased reflexes	Very often (80–99%)
Mental deterioration	Very often (80–99%)
Abnormal cerebral white matter morphology	Often (30–79%)
Abnormal gait	Often (30–79%)
Abnormality of balance	Often (30–79%)
Aggressive behavior	Often (30–79%)
Anxiety	Often (30–79%)
Ataxia	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Boiling mad	Often (30–79%)
Clumsiness	Often (30–79%)
Decreased muscle movement	Often (30–79%)
Delusions	Often (30–79%)
Dementia	Often (30–79%)
Depression	Often (30–79%)
Disinhibition	Often (30–79%)
Epilepsy	Often (30–79%)
Hallucinations	Often (30–79%)
Inability to coordinate movements when walking	Often (30–79%)
Involuntary movements	Often (30–79%)
Irritability	Often (30–79%)
Jerking	Often (30–79%)
Lack of feeling, emotion, interest	Often (30–79%)
Memory impairment	Often (30–79%)
Mental slowness	Often (30–79%)
More active than typical	Often (30–79%)
Neuronal loss in basal ganglia	Often (30–79%)
Obsessive compulsive behavior	Often (30–79%)
Poor fine motor coordination	Often (30–79%)
Speech articulation difficulties	Often (30–79%)
Wide based walk	Often (30–79%)
Addictive alcohol use	Sometimes (5–29%)
Babinski sign	Sometimes (5–29%)
Choking episodes	Sometimes (5–29%)
Clonus	Sometimes (5–29%)
Degeneration of cerebellum	Sometimes (5–29%)
Degeneration of the striatum	Sometimes (5–29%)
Difficulty staying or falling asleep	Sometimes (5–29%)
Excessive daytime sleepiness	Sometimes (5–29%)
Impaired visuospatial constructive cognition	Sometimes (5–29%)
Inability to speak	Sometimes (5–29%)
Inability to walk	Sometimes (5–29%)
Increased appetite	Sometimes (5–29%)
Progressive cerebellar ataxia	Sometimes (5–29%)
Suicidal ideation	Sometimes (5–29%)
Ventriculomegaly	Sometimes (5–29%)
Absent speech development	Not recorded
Gliosis	Not recorded
Loss of brain cells	Not recorded
Personality changes	Not recorded
Teeth grinding	Not recorded
Unsteady walk	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Generalized muscle weakness	Often (30–79%)
Oral motor hypotonia	Often (30–79%)
Rigidity	Often (30–79%)
Hunched back	Not recorded
Involuntary muscle stiffness, contraction, or spasm	Not recorded
Low muscle tone in trunk	Not recorded
Scoliosis	Not recorded
Spasticity and rigidity of muscles	Not recorded

Abnormality of the eye

Trait	How often it is seen
Abnormal involuntary eye movements	Often (30–79%)
Abnormality of eye movement	Often (30–79%)
Staring gaze	Often (30–79%)
Close sighted	Not recorded

Abnormality of limbs

Trait	How often it is seen
Abnormal rhythmic movements of ankle	Not recorded
Short foot	Not recorded
Small hand	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Oral-pharyngeal dysphagia	Sometimes (5–29%)
Feeding difficulties	Not recorded
Poor swallowing	Not recorded

Growth abnormality

Trait	How often it is seen
Weight loss	Often (30–79%)
Decreased body mass index	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Abnormality of the sense of smell	Often (30–79%)

Abnormality of the genitourinary system

Trait	How often it is seen
Abnormal libido	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
Abnormality of cholesterol metabolism	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 HTT and how often each is seen. Find out more at hpo.jax.org.

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