Traits

Traits linked to IARS2

isoleucyl-tRNA synthetase 2, mitochondrial

The Human Phenotype Ontology links 164 traits to IARS2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Decreased sensation in extremities	Always
Motor delay	Always
Pain insensitivity	Always
Peripheral neuropathy	Always
Too much cerebrospinal fluid in the brain	Always
Abnormality of movement	Very often (80–99%)
Abnormal basal ganglia MRI signal intensity	Often (30–79%)
Abnormal brainstem MRI signal intensity	Often (30–79%)
Abnormal dentate nucleus morphology	Often (30–79%)
Abnormal thalamic MRI signal intensity	Often (30–79%)
Brain imaging abnormality	Often (30–79%)
Diffuse spongiform leukoencephalopathy	Often (30–79%)
Elevated brain lactate level by MRS	Often (30–79%)
Focal T2 hyperintense basal ganglia lesion	Often (30–79%)
Focal T2 hyperintense brainstem lesion	Often (30–79%)
Gliosis	Often (30–79%)
Global developmental delay	Often (30–79%)
Involuntary movements	Often (30–79%)
Leukodystrophy	Often (30–79%)
Loss of developmental milestones	Often (30–79%)
Upper motor neuron dysfunction	Often (30–79%)
Worsening neurological symptoms	Often (30–79%)
Abnormality of extrapyramidal motor function	Sometimes (5–29%)
Agenesis of corpus callosum	Sometimes (5–29%)
Ataxia	Sometimes (5–29%)
Chorea	Sometimes (5–29%)
Choreoathetosis	Sometimes (5–29%)
Dystonia	Sometimes (5–29%)
Epilepsy	Sometimes (5–29%)
Hyperactive movements	Sometimes (5–29%)
Hypsarrhythmia	Sometimes (5–29%)
Involuntary writhing movements in fingers, hands, toes, and feet	Sometimes (5–29%)
Neuronal loss in basal ganglia	Sometimes (5–29%)
Olivopontocerebellar atrophy	Sometimes (5–29%)
Sensory axonal neuropathy	Sometimes (5–29%)
Underdevelopment of part of brain called corpus callosum	Sometimes (5–29%)
Degeneration of cerebellum	Rarely (1–4%)
Disorder of involuntary muscle movements	Rarely (1–4%)
Encephalomalacia	Rarely (1–4%)
Infantile spasms	Rarely (1–4%)
Repeated seizures without recovery between them	Rarely (1–4%)
Damage to nerves that sense feeling	Not recorded
Decrease in size of the outer layer of the brain due to loss of brain cells	Not recorded
Decreased reflex response	Not recorded
Nerve damage causing decreased feeling and movement	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Coronal cleft vertebrae	Always
Delayed maturation of end part of long bone	Always
Double-Jointed	Always
Low muscle tone	Always
Scoliosis	Always
Short long bone	Always
Shorter than typical length between neck and abdomen	Always
Spondyloepimetaphyseal dysplasia	Always
Abnormal skeletal development	Very often (80–99%)
Cervical spinal canal stenosis	Very often (80–99%)
Decreased muscle tone in infant	Very often (80–99%)
Narrow spinal canal	Very often (80–99%)
Spondyloepiphyseal dysplasia	Very often (80–99%)
Thoracic kyphoscoliosis	Very often (80–99%)
Hypoplasia of the odontoid process	Often (30–79%)
Abnormality of the skeletal system	Sometimes (5–29%)
Involuntary muscle stiffness, contraction, or spasm	Sometimes (5–29%)
Multiple joint contractures	Sometimes (5–29%)
Muscle degeneration	Sometimes (5–29%)
Muscle tissue disease	Sometimes (5–29%)
Muscle weakness	Sometimes (5–29%)
Spastic diplegia	Sometimes (5–29%)
Weakness of outermost muscles	Sometimes (5–29%)
Flexed joint that cannot be straightened	Not recorded
Osteopenia	Not recorded
Prominent swayback	Not recorded

Abnormality of head or neck

Trait	How often it is seen
Crease in skin under the eye	Always
Decreased volume of lip	Always
Depressed nasal bridge	Always
Little foramen magnum	Always
Little lower jaw	Always
Short nose	Always
Underdeveloped tissue around nostril	Always
Narrow mouth	Very often (80–99%)
Prominent forehead	Very often (80–99%)
Thick eyebrow	Very often (80–99%)
Abnormal facial shape	Rarely (1–4%)
Hairy forehead	Rarely (1–4%)
High forehead	Rarely (1–4%)
Big lower jaw	Not recorded
Dry eye syndrome	Not recorded
Flat forehead	Not recorded
Long philtrum	Not recorded
Midface retrusion	Not recorded

Laboratory abnormality

Trait	How often it is seen
Low blood sugar	Always
Abnormal circulating enzyme concentration or activity	Very often (80–99%)
High urine lactic acid levels	Very often (80–99%)
Higher than normal levels of lactate in blood	Very often (80–99%)
Increased CSF lactate	Very often (80–99%)
Increased lactate in body	Very often (80–99%)
Low blood sugar when fasting	Very often (80–99%)
Complex organic aciduria	Often (30–79%)
3-Methylglutaconic aciduria	Sometimes (5–29%)
Decreased circulating biotinidase concentration	Sometimes (5–29%)
Ethylmalonic aciduria	Sometimes (5–29%)
Generalized aminoaciduria	Sometimes (5–29%)
Increased blood alanine	Sometimes (5–29%)
Ketoacidosis	Sometimes (5–29%)
Methylmalonic aciduria	Sometimes (5–29%)
Accumulation of acid in body due to kidney problem	Rarely (1–4%)

Abnormality of the eye

Trait	How often it is seen
Clouding of the lens of the eye	Always
Farsightedness	Always
Involuntary, rapid, rhythmic eye movements	Always
Clouding of the lens of the eye at birth	Very often (80–99%)
Eye muscle paralysis	Often (30–79%)
Optic atrophy	Often (30–79%)
Optic nerve issue	Often (30–79%)
Drooping upper eyelid	Sometimes (5–29%)
Cross-eyed	Not recorded
Deeply set eye	Not recorded
Horizontal nystagmus	Not recorded
Inward turning cross eyed	Not recorded

Abnormality of limbs

Trait	How often it is seen
Flared wide portion of long bone	Always
Hip dislocation	Always
Irregular wide portion of a long bone	Always
Knock knees	Very often (80–99%)
Dislocated hip since birth	Often (30–79%)
Dropped arches	Not recorded
Short fingers or toes	Not recorded
Tapered finger	Not recorded

Abnormal cellular phenotype

Trait	How often it is seen
Decreased activity of mitochondrial complex I	Often (30–79%)
Decreased activity of mitochondrial respiratory chain	Often (30–79%)
Decreased activity of the pyruvate dehydrogenase complex	Often (30–79%)
Decreased activity of mitochondrial complex III	Sometimes (5–29%)
Decreased activity of mitochondrial complex IV	Sometimes (5–29%)
Decreased activity of mitochondrial complex II	Rarely (1–4%)

Abnormality of the digestive system

Trait	How often it is seen
Achalasia	Very often (80–99%)
Feeding difficulties	Often (30–79%)
Liver failure	Sometimes (5–29%)
Poor swallowing	Sometimes (5–29%)
Gastrointestinal dysmotility	Rarely (1–4%)

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Always
Bilateral sensorineural hearing impairment	Very often (80–99%)
Prelingual sensorineural hearing impairment	Very often (80–99%)
Progressive sensorineural hearing impairment	Very often (80–99%)
Large ears	Rarely (1–4%)

Abnormality of the cardiovascular system

Trait	How often it is seen
Telangiectasia of the skin	Always
Enlarged and thickened heart muscle	Often (30–79%)
Cardiac failure	Sometimes (5–29%)
Hole in heart wall separating two lower heart chambers	Rarely (1–4%)

Abnormality of the integument

Trait	How often it is seen
Poikiloderma	Always
Periarticular subcutaneous nodules	Very often (80–99%)
Excessive hair growth	Often (30–79%)
Hair loss	Rarely (1–4%)

Growth abnormality

Trait	How often it is seen
Growth delay	Always
Short stature	Always
Faltering weight	Often (30–79%)
Prenatal growth deficiency	Rarely (1–4%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Low number of red blood cells or hemoglobin	Sometimes (5–29%)
Low blood neutrophil count	Rarely (1–4%)

Abnormality of the endocrine system

Trait	How often it is seen
Decreased response to growth hormone stimulation test	Always
Central adrenal insufficiency	Not recorded

Abnormality of the genitourinary system

Trait	How often it is seen
Abnormal function of filtrating structures in kidney	Rarely (1–4%)
Nephrotic syndrome	Rarely (1–4%)

Abnormality of the immune system

Trait	How often it is seen
Severe viral infection	Often (30–79%)
Eczema	Rarely (1–4%)

Abnormality of the respiratory system

Trait	How often it is seen
Abnormal pattern of respiration	Sometimes (5–29%)
Respiratory failure	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

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 IARS2 and how often each is seen. Find out more at hpo.jax.org.

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