Traits

Traits linked to MTHFR

methylenetetrahydrofolate reductase

The Human Phenotype Ontology links 85 traits to MTHFR, by body system: features seen in people with one of the gene's rare conditions.

MTHFR

Abnormality of the nervous system

Trait	How often it is seen
Abnormal gait	Very often (80–99%)
Behavioral abnormality	Very often (80–99%)
Morphological central nervous system abnormality	Very often (80–99%)
Upper motor neuron dysfunction	Very often (80–99%)
Abnormal periventricular white matter morphology	Often (30–79%)
Abnormal shape of brain	Often (30–79%)
Absent/small cerebellum	Often (30–79%)
Agenesis of corpus callosum	Often (30–79%)
Ataxia	Often (30–79%)
Brain imaging abnormality	Often (30–79%)
Epilepsy	Often (30–79%)
Holoprosencephaly	Often (30–79%)
Mental deterioration	Often (30–79%)
Peripheral neuropathy	Often (30–79%)
Psychotic episodes	Often (30–79%)
Abnormal cerebral white matter morphology	Sometimes (5–29%)
Brain degeneration	Sometimes (5–29%)
Cognitive impairment	Sometimes (5–29%)
Degeneration of the spinal cord	Sometimes (5–29%)
Global developmental delay	Sometimes (5–29%)
Grand mal seizures	Sometimes (5–29%)
Headache	Sometimes (5–29%)
Intellectual disability	Sometimes (5–29%)
Lethargy	Sometimes (5–29%)
Psychosis	Sometimes (5–29%)
Psychotic mentation	Sometimes (5–29%)
Seizure affecting one half of brain	Sometimes (5–29%)
Specific learning disability	Sometimes (5–29%)
Weakness of one side of body	Sometimes (5–29%)
Brief seizures with staring spells	Rarely (1–4%)
Encephalopathy	Rarely (1–4%)
Generalized myoclonic seizure	Rarely (1–4%)
Too much cerebrospinal fluid in the brain	Rarely (1–4%)
Ventriculomegaly	Rarely (1–4%)
Delusions	Not recorded
EEG abnormality	Not recorded
Hallucinations	Not recorded
Incoordination	Not recorded
Negativism	Not recorded
Pins and needles feeling	Not recorded
Schizophrenia	Not recorded
Social and occupational deterioration	Not recorded
Spinal dysraphism	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Abnormality of cranium	Often (30–79%)
Abnormality of the skull	Often (30–79%)
Decreased size of bone of forehead	Often (30–79%)
Abnormality of facial bones	Sometimes (5–29%)
Cleft lip	Sometimes (5–29%)
Depressed nasal bridge	Sometimes (5–29%)
Abnormally small head	Rarely (1–4%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Abnormal blood clot	Sometimes (5–29%)
Blood clot in a deep vein	Sometimes (5–29%)
Thromboembolic stroke	Sometimes (5–29%)
Blood clot in cerebral vein	Not recorded
Recurrent thrombophlebitis	Not recorded
Thromboembolism	Not recorded

Laboratory abnormality

Trait	How often it is seen
Abnormal circulating enzyme concentration or activity	Very often (80–99%)
Elevated blood homocystine	Very often (80–99%)
High blood cystathionine levels	Very often (80–99%)
High urine homocystine levels	Very often (80–99%)
Decreased plasma methionine	Often (30–79%)
Laboratory abnormality	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Lower limb spasticity	Very often (80–99%)
Spastic paraparesis	Often (30–79%)
Congenital diaphragmatic hernia	Sometimes (5–29%)
Generalized low muscle tone in neonate	Sometimes (5–29%)
Muscle weakness	Not recorded

Abnormality of the eye

Trait	How often it is seen
Bulging eye	Often (30–79%)
Abnormality of the eye	Rarely (1–4%)
Involuntary, rapid, rhythmic eye movements	Rarely (1–4%)
Optic atrophy	Rarely (1–4%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Enlarged thymus	Sometimes (5–29%)
Stroke	Rarely (1–4%)
Blood clot in artery of lung	Not recorded

Abnormality of the endocrine system

Trait	How often it is seen
Small adrenal glands	Often (30–79%)
Posterior pituitary agenesis	Sometimes (5–29%)
Underdeveloped pituitary gland	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Feeding difficulties in infancy	Sometimes (5–29%)
Omphalocele	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Prenatal growth deficiency	Often (30–79%)
Faltering weight	Sometimes (5–29%)

Abnormality of limbs

Trait	How often it is seen
Lower limb muscle weakness	Very often (80–99%)

Abnormality of prenatal development or birth

Trait	How often it is seen
High levels of amniotic fluid	Often (30–79%)

Abnormality of the ear

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

Abnormality of the respiratory system

Trait	How often it is seen
Apnea	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 MTHFR and how often each is seen. Find out more at hpo.jax.org.

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