Traits

Traits linked to SPR

sepiapterin reductase

The Human Phenotype Ontology links 38 traits to SPR, 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
Global developmental delay	Always
Aggressive behavior	Often (30–79%)
Ataxia	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Cognitive impairment	Often (30–79%)
Delayed speech and language development	Often (30–79%)
Depression	Often (30–79%)
Difficulty sleeping	Often (30–79%)
Drowsiness	Often (30–79%)
Dystonia	Often (30–79%)
Increased reflexes	Often (30–79%)
Intellectual disability	Often (30–79%)
Motor delay	Often (30–79%)
Oculogyric crisis	Often (30–79%)
Slow movements	Often (30–79%)
Tremor	Often (30–79%)
Cerebral palsy	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Choreoathetosis	Not recorded
Difficulty articulating speech	Not recorded
More active than typical	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Involuntary muscle stiffness, contraction, or spasm	Always
Frequent falls	Often (30–79%)
Low muscle tone in trunk	Often (30–79%)
Muscle weakness	Often (30–79%)
Rigidity	Often (30–79%)

Abnormality of head or neck

Trait	How often it is seen
Abnormality of the nose	Often (30–79%)
Abnormally small head	Often (30–79%)
Decreased facial expressions	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
Reduced sepiapterin reductase activity in cultured fibroblasts	Always
Temperature instability	Often (30–79%)
Transient hyperphenylalaninemia	Not recorded

Abnormality of the eye

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

Growth abnormality

Trait	How often it is seen
Growth delay	Often (30–79%)
Small for gestational age	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Increased muscle tone of arm or leg	Often (30–79%)

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 SPR and how often each is seen. Find out more at hpo.jax.org.

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