Traits

Traits linked to SMPX

small muscle protein X-linked

The Human Phenotype Ontology links 13 traits to SMPX, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of limbs

Trait	How often it is seen
Distal lower limb muscle weakness	Always
Distal upper limb muscle weakness	Often (30–79%)
Proximal lower limb muscle weakness	Often (30–79%)
Proximal upper limb muscle weakness	Often (30–79%)
Winged shoulder blade	Often (30–79%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Fatty replacement of skeletal muscle	Very often (80–99%)
Centrally nucleated skeletal muscle fibers	Often (30–79%)
Increased variability in muscle fiber diameter	Often (30–79%)
Rimmed vacuoles	Often (30–79%)

Abnormality of the ear

Trait	How often it is seen
Hearing loss, high-frequency	Not recorded
Sensorineural hearing impairment	Not recorded

Abnormal cellular phenotype

Trait	How often it is seen
Muscle fiber cytoplasmatic inclusion bodies	Often (30–79%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Myofiber disarray	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 SMPX and how often each is seen. Find out more at hpo.jax.org.

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