Traits

Traits linked to AASS

aminoadipate-semialdehyde synthase

The Human Phenotype Ontology links 76 traits to AASS, 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
More active than typical	Always
Behavioral abnormality	Often (30–79%)
Clumsiness	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Difficulty performing quick and alternating movements	Often (30–79%)
EEG with spike-wave complexes	Often (30–79%)
Epilepsy	Often (30–79%)
Febrile seizure (within the age range of 3 months to 6 years)	Often (30–79%)
Global developmental delay	Often (30–79%)
Intellectual disability	Often (30–79%)
Intellectual disability, mild	Often (30–79%)
Neurodevelopmental delay	Often (30–79%)
Short attention span	Often (30–79%)
Abnormality of movement	Sometimes (5–29%)
Brisk reflexes	Sometimes (5–29%)
Cognitive impairment	Sometimes (5–29%)
Decreased sensation in extremities	Sometimes (5–29%)
Inability to coordinate movements when walking	Sometimes (5–29%)
Incoordination	Sometimes (5–29%)
Intellectual disability, borderline	Sometimes (5–29%)
Lack of coordination of movement	Sometimes (5–29%)
Mental deterioration	Sometimes (5–29%)
Mild global developmental delay	Sometimes (5–29%)
Simple febrile seizure	Sometimes (5–29%)
Toe walking	Sometimes (5–29%)
Tremor	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Decreased blood ornithine concentrations	Always
Decreased CSF arginine concentration	Always
Elevated blood lysine	Always
High urine arginine levels	Always
High urine lysine levels	Always
Homocitrullinuria	Always
Increased CSF lysine concentration	Always
Ornithinuria	Always
Abnormal circulating enzyme concentration	Very often (80–99%)
Abnormal circulating enzyme concentration or activity	Often (30–79%)
Abnormal CSF ornithine concentration	Often (30–79%)
Decreased urine alpha-ketoglutarate concentration	Often (30–79%)
High blood ammonia levels	Often (30–79%)
High urine cystine levels	Often (30–79%)
Citrullinuria	Sometimes (5–29%)
Elevated circulating citrulline concentration	Sometimes (5–29%)
High blood cystine levels	Sometimes (5–29%)
Elevated CSF saccharopine concentration	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Abnormally small head	Often (30–79%)
Abnormal facial shape	Sometimes (5–29%)
Deformity of the skull	Sometimes (5–29%)
Flat nose	Sometimes (5–29%)
High palate	Sometimes (5–29%)
Smooth philtrum	Sometimes (5–29%)
Thin eyebrow	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Acid reflux	Sometimes (5–29%)
Feeding difficulties	Sometimes (5–29%)
Nasogastric tube feeding	Sometimes (5–29%)
Poor suck	Sometimes (5–29%)
Poor swallowing	Sometimes (5–29%)
Vomiting	Sometimes (5–29%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Decreased muscle tone in infant	Often (30–79%)
Neck hypertonia	Sometimes (5–29%)
Opisthotonus	Sometimes (5–29%)
Spastic diplegia	Sometimes (5–29%)
Spastic tetraparesis	Sometimes (5–29%)
Low muscle tone	Not recorded

Abnormality of the eye

Trait	How often it is seen
Optic nerve hypoplasia	Often (30–79%)
Abnormally close eyes	Sometimes (5–29%)
Cross-eyed	Sometimes (5–29%)
Upgaze palsy	Sometimes (5–29%)
Ectopia lentis	Not recorded

Growth abnormality

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

Abnormality of the ear

Trait	How often it is seen
Hypoplasia of the antihelix	Sometimes (5–29%)
Hypoplastic helices	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Low number of red blood cells or hemoglobin	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Underdeveloped lung artery	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Recurrent pneumonia	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 AASS and how often each is seen. Find out more at hpo.jax.org.

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