Traits

Traits linked to HDAC9

histone deacetylase 9

The Human Phenotype Ontology links 10 traits to HDAC9, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of head or neck

Trait	How often it is seen
Full cheeks	Very often (80–99%)
Narrow mouth	Very often (80–99%)
Facial asymmetry	Often (30–79%)
Little lower jaw	Often (30–79%)
Retraction of the tongue	Often (30–79%)
Cleft palate	Sometimes (5–29%)
Skin tag behind the ear	Sometimes (5–29%)

Abnormality of the ear

Trait	How often it is seen
Hearing impairment	Always
Question mark ear	Very often (80–99%)

Abnormality of the respiratory system

Trait	How often it is seen
Apnea	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 HDAC9 and how often each is seen. Find out more at hpo.jax.org.

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