Traits

Traits linked to MTM1

myotubularin 1

The Human Phenotype Ontology links 62 traits to MTM1, 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
Low muscle tone, in neonatal onset	Always
Generalized decreased muscle tone	Very often (80–99%)
Type 1 fibers relatively smaller than type 2 fibers	Very often (80–99%)
Centrally nucleated skeletal muscle fibers	Often (30–79%)
Fatigable weakness of bulbar muscles	Often (30–79%)
Fatigable weakness of swallowing muscles	Often (30–79%)
Necklace skeletal muscle fibers	Often (30–79%)
Severely decreased muscle tone	Often (30–79%)
Double-Jointed	Sometimes (5–29%)
Thin ribs	Sometimes (5–29%)
Diaphragmatic eventration	Not recorded
Flexed joint that cannot be straightened	Not recorded
Generalized muscle weakness	Not recorded
Neck muscle weakness	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Weakness of facial musculature	Often (30–79%)
Abnormal facial shape	Sometimes (5–29%)
High palate	Sometimes (5–29%)
Long face	Sometimes (5–29%)
Long, narrow head	Sometimes (5–29%)
Receding chin	Sometimes (5–29%)
Dandy-Walker malformation	Rarely (1–4%)
Bad bite	Not recorded
Bell's palsy	Not recorded
Big calvaria	Not recorded
High forehead	Not recorded
Narrow face	Not recorded

Abnormality of prenatal development or birth

Trait	How often it is seen
Low 1-minute APGAR score	Very often (80–99%)
Low APGAR score	Very often (80–99%)
Caesarean section	Often (30–79%)
High levels of amniotic fluid	Often (30–79%)
Less than 10 fetal movements in 12 hours	Often (30–79%)
Low 5-minute APGAR score	Often (30–79%)
Premature birth	Often (30–79%)

Abnormality of the genitourinary system

Trait	How often it is seen
Blind vagina	Often (30–79%)
Cleft of scrotum	Often (30–79%)
Glanular hypospadias	Often (30–79%)
Penile hypospadias	Often (30–79%)
Penoscrotal hypospadias	Often (30–79%)
Short penis	Often (30–79%)
Undescended testes	Often (30–79%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties in infancy	Often (30–79%)
Poor suck	Often (30–79%)
Feeding difficulties	Sometimes (5–29%)
Pyloric stenosis	Not recorded
Tube feeding	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Absent reflexes	Often (30–79%)
Inability to walk	Sometimes (5–29%)
Decreased muscle movement	Not recorded
Motor delay	Not recorded
Too much cerebrospinal fluid in the brain	Not recorded

Abnormality of the respiratory system

Trait	How often it is seen
Neonatal respiratory distress	Very often (80–99%)
Respiratory failure requiring assisted ventilation	Very often (80–99%)
Breathing difficulties	Often (30–79%)
Respiratory function loss	Often (30–79%)

Abnormality of limbs

Trait	How often it is seen
Long slender fingers	Often (30–79%)
Slender toe	Not recorded

Abnormality of the eye

Trait	How often it is seen
Abnormality of the eye	Often (30–79%)
Paralysis or weakness of muscles within or surrounding outer part of eye	Not recorded

Abnormality of the immune system

Trait	How often it is seen
Pneumonia	Often (30–79%)
Recurrent respiratory infections	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Birth length greater than 97th percentile	Often (30–79%)

Laboratory abnormality

Trait	How often it is seen
High liver enzymes	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 MTM1 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