Traits

Traits linked to SMN2

survival of motor neuron 2, centromeric

The Human Phenotype Ontology links 19 traits to SMN2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of limbs

Trait	How often it is seen
Absent ankle reflexes	Always
Absent knee jerk reflex	Always
Lower limb muscle weakness	Always
Pelvic girdle amyotrophy	Always
Pelvic girdle muscle weakness	Always
Wasting of thigh muscle	Always
Weak shoulder muscles	Always
Shoulder girdle muscle wasting	Often (30–79%)
Limb fasciculations	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
EMG: chronic denervation signs	Always
Proximal neurogenic muscle weakness	Always
Distal muscle wasting	Often (30–79%)
Muscle spasm	Often (30–79%)
Spinal muscle degeneration	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Loss of ability to walk	Often (30–79%)
Decreased reflex response	Not recorded
Degeneration of anterior horn cells	Not recorded
Hand tremor	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Tongue twitching	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 SMN2 and how often each is seen. Find out more at hpo.jax.org.

One test. A lifetime of answers.

From $449Free shipping · Results in 6–8 weeks

Get my Genome Test