Traits

Traits linked to SLC6A9

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The Human Phenotype Ontology links 35 traits to SLC6A9, 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
Abnormally small head	Sometimes (5–29%)
Depressed nasal bridge	Not recorded
Long eyelashes	Not recorded
Long, narrow head	Not recorded
Myopathic facies	Not recorded
Nasal tip, upturned	Not recorded
Receding chin	Not recorded
Triangular head shape	Not recorded

Abnormality of limbs

Trait	How often it is seen
Back knee	Not recorded
Club feet	Not recorded
Elbow flexion contracture	Not recorded
Hand clenching	Not recorded
Hip contracture	Not recorded
Hip dislocation	Not recorded
Overlapping toe	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Arthrogryposis multiplex congenita	Not recorded
Double-Jointed	Not recorded
Flexed joint that cannot be straightened	Not recorded
Low muscle tone in trunk	Not recorded
Scoliosis	Not recorded
Spasticity and rigidity of muscles	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Clonus	Not recorded
Encephalopathy	Not recorded
Exaggerated startle response	Not recorded
Global developmental delay	Not recorded
Underdevelopment of part of brain called corpus callosum	Not recorded
Ventriculomegaly	Not recorded

Abnormality of the eye

Trait	How often it is seen
Optic atrophy	Often (30–79%)
Drooping upper eyelid	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Apnea	Not recorded
Respiratory failure	Not recorded

Abnormality of prenatal development or birth

Trait	How often it is seen
Fetal distress	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Poor swallowing	Not recorded

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Not recorded

Laboratory abnormality

Trait	How often it is seen
Elevated blood glycine levels	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 SLC6A9 and how often each is seen. Find out more at hpo.jax.org.

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