Traits

Traits linked to DDC

dopa decarboxylase

The Human Phenotype Ontology links 60 traits to DDC, 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
Diminished movement	Always
Involuntary writhing movements in fingers, hands, toes, and feet	Always
Limb dystonia	Always
Oculogyric crisis	Always
Can't control feelings	Very often (80–99%)
Global developmental delay	Very often (80–99%)
Irritability	Very often (80–99%)
Tongue thrusting	Very often (80–99%)
Behavioral abnormality	Often (30–79%)
Difficulty sleeping	Often (30–79%)
Dystonia	Often (30–79%)
Epilepsy	Often (30–79%)
Exaggerated startle response	Often (30–79%)
Increased reflexes	Often (30–79%)
Intellectual disability	Often (30–79%)
Jerking	Often (30–79%)
Lethargy	Often (30–79%)
Limb tremor	Often (30–79%)
Motor delay	Often (30–79%)
Autism spectrum disorder	Sometimes (5–29%)
Babinski sign	Sometimes (5–29%)
Decreased muscle movement	Sometimes (5–29%)
Difficulty articulating speech	Sometimes (5–29%)
Diminished deep tendon reflex	Sometimes (5–29%)
Disorder of involuntary muscle movements	Sometimes (5–29%)
EEG abnormality	Sometimes (5–29%)
Tremor	Rarely (1–4%)
Choreoathetosis	Not recorded

Laboratory abnormality

Trait	How often it is seen
Decreased CSF 5-hydroxyindolacetic acid concentration	Very often (80–99%)
Decreased CSF homovanillic acid concentration	Very often (80–99%)
Low blood sugar	Sometimes (5–29%)
Elevated urinary vanillactic acid level	Not recorded
Intermittent hypothermia	Not recorded
Reduced circulating aromatic L-amino acid decarboxylase activity	Not recorded
Temperature instability	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Very often (80–99%)
Constipation	Often (30–79%)
Diarrhea	Often (30–79%)
Feeding difficulties	Often (30–79%)
Feeding difficulties in infancy	Often (30–79%)
Poor swallowing	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Blockage of nose	Often (30–79%)
Eyelid spasm	Often (30–79%)
Wry neck	Often (30–79%)
Drooling	Sometimes (5–29%)
Abnormality of the face	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone in trunk	Always
Low muscle tone	Often (30–79%)
Poor head control	Often (30–79%)
Joint contracture	Rarely (1–4%)

Abnormality of the eye

Trait	How often it is seen
Drooping upper eyelid	Often (30–79%)
Constricted pupils	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Apnea	Often (30–79%)
Cardiorespiratory arrest	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Often (30–79%)
Short stature	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Increased muscle tone of arm or leg	Always

Abnormality of the cardiovascular system

Trait	How often it is seen
Low blood pressure	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Increased circulating prolactin concentration	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Excessive sweating	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 DDC and how often each is seen. Find out more at hpo.jax.org.

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