Traits

Traits linked to ACTA1

actin alpha 1, skeletal muscle

The Human Phenotype Ontology links 181 traits to ACTA1, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the musculoskeletal system

Trait	How often it is seen
Abnormality of skeletal muscle fiber size	Always
Generalized decreased muscle tone	Always
Generalized muscle weakness	Always
Increased connective tissue	Always
Increased endomysial connective tissue	Always
Increased variability in muscle fiber diameter	Always
Joint contracture	Always
Low muscle tone	Always
Muscle degeneration	Always
Neck flexion weakness	Always
Poor head control	Always
Type 1 muscle fiber predominance	Always
Abnormally shaped skeletal	Very often (80–99%)
Autophagic vacuoles	Very often (80–99%)
Axial muscle weakness	Very often (80–99%)
Difficulty walking up stairs	Very often (80–99%)
EMG: myopathic abnormalities	Very often (80–99%)
Gowers sign	Very often (80–99%)
Handgrip myotonia	Very often (80–99%)
Low muscle tone, in neonatal onset	Very often (80–99%)
Muscle fiber splitting	Very often (80–99%)
Muscle tissue disease	Very often (80–99%)
Myofibrillar myopathy	Very often (80–99%)
Neck muscle weakness	Very often (80–99%)
Progressive muscle weakness	Very often (80–99%)
Proximal neurogenic muscle weakness	Very often (80–99%)
Reduced spine movement	Very often (80–99%)
Rimmed vacuoles	Very often (80–99%)
Scoliosis	Very often (80–99%)
Severely decreased muscle tone	Very often (80–99%)
Type 1 muscle fiber atrophy	Very often (80–99%)
Weakness of outermost muscles	Very often (80–99%)
Abnormality of the chest	Often (30–79%)
Decreased lung function due to weak breathing muscles	Often (30–79%)
Fatigable weakness of bulbar muscles	Often (30–79%)
Fatigable weakness of distal limb muscles	Often (30–79%)
Flexed joint that cannot be straightened	Often (30–79%)
Generalized muscle wasting	Often (30–79%)
Hamstring contractures	Often (30–79%)
Multiple fractures present at birth	Often (30–79%)
Muscle fiber necrosis	Often (30–79%)
Muscle stiffness	Often (30–79%)
Prominent swayback	Often (30–79%)
Thoracic scoliosis	Often (30–79%)
Tired easily	Often (30–79%)
Weakness of muscles of respiration	Often (30–79%)
Abnormality of the diaphragm	Sometimes (5–29%)
Arthrogryposis multiplex congenita	Sometimes (5–29%)
Fatigable weakness of respiratory muscles	Sometimes (5–29%)
Fatiguable weakness of proximal limb muscles	Sometimes (5–29%)
Funnel chest	Sometimes (5–29%)
Kyphoscoliosis	Sometimes (5–29%)
Muscle weakness between ribs	Sometimes (5–29%)
Narrow chest	Sometimes (5–29%)
Poorly developed skeletal musculature	Sometimes (5–29%)
Rigidity	Sometimes (5–29%)
Spasticity and rigidity of muscles	Sometimes (5–29%)
Thin ribs	Sometimes (5–29%)
Hunched back	Rarely (1–4%)
Bulbar palsy	Not recorded
Centrally nucleated skeletal muscle fibers	Not recorded
EMG: neuropathic changes	Not recorded
Frequent falls	Not recorded
Late-onset distal muscle weakness	Not recorded

Abnormality of limbs

Trait	How often it is seen
Joint contracture of the hand	Always
Limb-girdle muscular dystrophy	Very often (80–99%)
Winged shoulder blade	Very often (80–99%)
Wrist drop	Very often (80–99%)
Elbow flexion contracture	Often (30–79%)
Foot drop	Often (30–79%)
Hip contracture	Often (30–79%)
Knee contracture	Often (30–79%)
Limb muscle weakness	Often (30–79%)
Limb-girdle muscle weakness	Often (30–79%)
Ankle flexion contracture	Sometimes (5–29%)
Club feet	Sometimes (5–29%)
Dislocated hip since birth	Sometimes (5–29%)
Flexion contracture of finger	Sometimes (5–29%)
High-arched foot	Sometimes (5–29%)
Hip dislocation	Sometimes (5–29%)
Inability to straighten knee	Sometimes (5–29%)
Inward turned thumb	Sometimes (5–29%)
Knock knees	Sometimes (5–29%)
Outward bow-leggedness	Sometimes (5–29%)
Pelvic girdle muscle weakness	Sometimes (5–29%)
Weak shoulder muscles	Sometimes (5–29%)
Hand muscle degeneration	Not recorded
Shortening of the achilles tendon	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Absent reflexes	Always
Delayed ability to sit	Always
Global developmental delay	Very often (80–99%)
Waddling gait	Very often (80–99%)
Abnormal gait	Often (30–79%)
Clumsiness	Often (30–79%)
Decreased muscle movement	Often (30–79%)
Decreased reflex response	Often (30–79%)
Delayed ability to roll over	Often (30–79%)
Diminished deep tendon reflex	Often (30–79%)
Motor delay	Often (30–79%)
Slow movements	Often (30–79%)
Bulbar signs	Sometimes (5–29%)
Difficulty sleeping	Sometimes (5–29%)
Falls	Sometimes (5–29%)
Headache	Sometimes (5–29%)
Increased reflexes	Sometimes (5–29%)
Tremor	Sometimes (5–29%)
Poor fine motor coordination	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Expressionless face	Always
Weakness of facial musculature	Always
Bell's palsy	Very often (80–99%)
Wry neck	Very often (80–99%)
Big lower jaw	Often (30–79%)
Dental crowding	Often (30–79%)
High palate	Often (30–79%)
Long face	Often (30–79%)
Myopathic facies	Often (30–79%)
Narrow face	Often (30–79%)
Chewing difficulties	Sometimes (5–29%)
Facial diplegia	Sometimes (5–29%)
High, narrow palate	Sometimes (5–29%)
Little lower jaw	Sometimes (5–29%)
Long philtrum	Sometimes (5–29%)
Short neck	Sometimes (5–29%)
Wide fontanelles	Sometimes (5–29%)
Receding chin	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Respiratory failure	Always
Respiratory failure requiring assisted ventilation	Always
Respiratory function loss	Always
Abnormality of the respiratory system	Often (30–79%)
Abnormality on pulmonary function testing	Often (30–79%)
Breathing difficulties	Often (30–79%)
High blood carbon dioxide level	Sometimes (5–29%)
Low blood oxygen level	Sometimes (5–29%)
Nocturnal hypoventilation	Sometimes (5–29%)
Poorly developed lungs	Sometimes (5–29%)
Reduced vital capacity	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties	Always
Tube feeding	Always
Poor swallowing	Very often (80–99%)
Gastrostomy tube feeding in infancy	Often (30–79%)
Nasogastric tube feeding	Often (30–79%)
Neuromuscular dysphagia	Often (30–79%)
Poor appetite	Often (30–79%)
Feeding difficulties in infancy	Sometimes (5–29%)
Nasogastric tube feeding in infancy	Sometimes (5–29%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Cardiac conduction abnormality	Often (30–79%)
Abnormality of the heart	Sometimes (5–29%)
Cor pulmonale	Sometimes (5–29%)
Disease of the heart muscle	Sometimes (5–29%)
Enlarged heart	Sometimes (5–29%)
Heart stops beating	Sometimes (5–29%)
Slow heartbeats	Sometimes (5–29%)
Stretched and thinned heart muscle	Sometimes (5–29%)

Abnormality of prenatal development or birth

Trait	How often it is seen
Feet or buttocks of fetus positioned near opening of uterus	Always
Less than 10 fetal movements in 12 hours	Very often (80–99%)
High levels of amniotic fluid	Often (30–79%)
Fetal akinesia sequence	Sometimes (5–29%)
Premature birth	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Chylothorax	Always
Elevated blood creatine phosphokinase	Very often (80–99%)
Increased muscle lipid content	Often (30–79%)
Edema of the dorsum of hands	Sometimes (5–29%)
Mildly elevated creatine kinase	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Drooping upper eyelid	Sometimes (5–29%)
Eye muscle paralysis	Sometimes (5–29%)
Wide-set eyes	Sometimes (5–29%)

Abnormality of the immune system

Trait	How often it is seen
Pneumonia	Often (30–79%)
Aspiration pneumonia	Sometimes (5–29%)
Recurrent respiratory infections	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Often (30–79%)
Weight loss	Often (30–79%)
Slender build	Sometimes (5–29%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Bleeding in brain	Always
Subdural hemorrhage	Always

Abnormality of the genitourinary system

Trait	How often it is seen
Hypospadias	Sometimes (5–29%)
Short penis	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Decreased ability to exercise	Often (30–79%)
Fatigue	Often (30–79%)

Abnormal cellular phenotype

Trait	How often it is seen
Nemaline bodies	Always

Abnormality of the ear

Trait	How often it is seen
Low-set ears	Sometimes (5–29%)

Abnormality of the voice

Trait	How often it is seen
Hoarse voice	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 ACTA1 and how often each is seen. Find out more at hpo.jax.org.

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