Traits

Traits linked to POLG

DNA polymerase gamma, catalytic subunit

The Human Phenotype Ontology links 285 traits to POLG, by body system: features seen in people with one of the gene's rare conditions.

POLG

Abnormality of the nervous system

Trait	How often it is seen
Ataxia	Always
Babinski sign	Always
Degeneration of cerebellum	Always
Degeneration of cerebrum	Always
Difficulty articulating speech	Always
Dystonia	Always
Inability to coordinate movements when walking	Always
Instability or lack of coordination of central trunk muscles	Always
Intention tremor	Always
Nerve damage causing decreased feeling and movement	Always
Numbness	Always
Parkinsonism	Always
Peripheral neuropathy	Always
Sensory ataxic neuropathy	Always
Slow movements	Always
Absent reflexes	Very often (80–99%)
Leukoencephalopathy	Very often (80–99%)
Abnormal cerebellar cortex morphology	Often (30–79%)
Abnormal cerebral white matter morphology	Often (30–79%)
Abnormal gait	Often (30–79%)
Abnormal thalamic MRI signal intensity	Often (30–79%)
Abnormality of central motor conduction	Often (30–79%)
Abnormality of movement	Often (30–79%)
Anxiety	Often (30–79%)
Atrophy/Degeneration involving the spinal cord	Often (30–79%)
Behavioral abnormality	Often (30–79%)
Bilateral tonic-clonic seizure with focal onset	Often (30–79%)
Cerebral infarct	Often (30–79%)
Choreoathetosis	Often (30–79%)
Cognitive impairment	Often (30–79%)
Coma	Often (30–79%)
Decreased motor nerve conduction velocity	Often (30–79%)
Decreased number of large peripheral myelinated nerve fibers	Often (30–79%)
Decreased reflex response	Often (30–79%)
Decreased sensory nerve conduction velocity	Often (30–79%)
Demyelinating peripheral neuropathy	Often (30–79%)
Depression	Often (30–79%)
Difficulty performing quick and alternating movements	Often (30–79%)
EEG with occipital epileptiform discharges	Often (30–79%)
Encephalopathy	Often (30–79%)
Epilepsia partialis continua	Often (30–79%)
Epilepsy	Often (30–79%)
Focal myoclonic seizure	Often (30–79%)
Focal T2 hyperintense thalamic lesion	Often (30–79%)
Generalized non-convulsive status epilepticus without coma	Often (30–79%)
Gliosis	Often (30–79%)
Global developmental delay	Often (30–79%)
Grand mal seizures	Often (30–79%)
Hand tremor	Often (30–79%)
Headache	Often (30–79%)
Impaired distal proprioception	Often (30–79%)
Impaired distal vibration sensation	Often (30–79%)
Impaired vibratory sensation	Often (30–79%)
Jerking	Often (30–79%)
Lack of coordination of movement	Often (30–79%)
Loss of developmental milestones	Often (30–79%)
Migraine	Often (30–79%)
Partial paralysis of legs	Often (30–79%)
Peripheral axonal neuropathy	Often (30–79%)
Pins and needles feeling	Often (30–79%)
Positive Romberg sign	Often (30–79%)
Progressive brain disease	Often (30–79%)
Progressive cerebellar ataxia	Often (30–79%)
Repeated seizures without recovery between them	Often (30–79%)
Resting tremor	Often (30–79%)
Seizure affecting one half of brain	Often (30–79%)
Sensory axonal neuropathy	Often (30–79%)
Slurred speech	Often (30–79%)
Tetraparesis	Often (30–79%)
Tremor	Often (30–79%)
Uncoordinated limb movement	Often (30–79%)
Vegetative state	Often (30–79%)
Worsening neurological symptoms	Often (30–79%)
Abnormal cerebrospinal fluid morphology	Sometimes (5–29%)
Abnormality of extrapyramidal motor function	Sometimes (5–29%)
Action tremor	Sometimes (5–29%)
Can't control feelings	Sometimes (5–29%)
Decreased muscle movement	Sometimes (5–29%)
Decreased sensation in extremities	Sometimes (5–29%)
Dementia	Sometimes (5–29%)
Focal white matter lesions	Sometimes (5–29%)
Intellectual disability	Sometimes (5–29%)
Lethargy	Sometimes (5–29%)
Memory impairment	Sometimes (5–29%)
Parkinsonism with favorable response to dopaminergic medication	Sometimes (5–29%)
Sensory ataxia	Sometimes (5–29%)
Shuffled walk	Sometimes (5–29%)
Stooped posture	Sometimes (5–29%)
Twitching	Sometimes (5–29%)
Bipolar disorder	Rarely (1–4%)
Astrocytosis	Not recorded
Cerebral cortical neurodegeneration	Not recorded
Decreased touch sensation in extremities	Not recorded
High stepping	Not recorded
Hypointensity of cerebral white matter on MRI	Not recorded
Limb ataxia	Not recorded
Loss of brain cells	Not recorded
Paralysis	Not recorded
Poor concentration	Not recorded
Progressive gait ataxia	Not recorded
Wide based walk	Not recorded

Abnormality of the musculoskeletal system

Trait	How often it is seen
Cytochrome C oxidase-negative muscle fibers	Always
Difficulty walking up stairs	Always
Increased variability in muscle fiber diameter	Always
Muscle fiber degeneration	Always
Muscle weakness	Always
Proximal neurogenic muscle weakness	Always
Ragged-red muscle fibers	Always
Scoliosis	Always
Weakness of outermost muscles	Always
EMG: myopathic abnormalities	Often (30–79%)
Fiber type grouping	Often (30–79%)
Generalized decreased muscle tone	Often (30–79%)
Involuntary muscle stiffness, contraction, or spasm	Often (30–79%)
Low muscle tone	Often (30–79%)
Mitochondrial myopathy	Often (30–79%)
Muscle tissue disease	Often (30–79%)
Neck flexion weakness	Often (30–79%)
Osteoporosis	Often (30–79%)
Progressive spasticity	Often (30–79%)
Spastic paraparesis	Often (30–79%)
Spasticity and rigidity of muscles	Often (30–79%)
Tired easily	Often (30–79%)
Centrally nucleated skeletal muscle fibers	Sometimes (5–29%)
Cogwheel rigidity	Sometimes (5–29%)
Decreased muscle mass	Sometimes (5–29%)
Diffuse skeletal muscle wasting	Sometimes (5–29%)
Frequent falls	Sometimes (5–29%)
Muscle degeneration	Sometimes (5–29%)
Muscle stiffness	Sometimes (5–29%)
Rigidity	Sometimes (5–29%)
Muscle spasm	Rarely (1–4%)
Breakdown of skeletal muscle	Not recorded
Decreased lung function due to weak breathing muscles	Not recorded
Distal muscle wasting	Not recorded
Generalized muscle weakness	Not recorded
Muscle fiber necrosis	Not recorded
Progressive muscle weakness	Not recorded
Subsarcolemmal accumulations of abnormally shaped mitochondria	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Intestinal pseudo-obstruction	Always
Poor swallowing	Always
Abdominal bloating	Very often (80–99%)
Abdominal cramps	Very often (80–99%)
Abdominal pain	Very often (80–99%)
Acid reflux	Very often (80–99%)
Atrophic muscularis propria	Very often (80–99%)
Diarrhea	Very often (80–99%)
Feeling full quickly when eating	Very often (80–99%)
Gastrointestinal dysmotility	Very often (80–99%)
Increased bowel sounds	Very often (80–99%)
Nausea	Very often (80–99%)
Poor appetite	Very often (80–99%)
Small intestinal dysmotility	Very often (80–99%)
Vomiting	Very often (80–99%)
Abnormality of the gastrointestinal tract	Often (30–79%)
Accumulation of fluid in the abdomen	Often (30–79%)
Acute liver failure	Often (30–79%)
Bile duct proliferation	Often (30–79%)
Colonic diverticula	Often (30–79%)
Delayed gastric emptying	Often (30–79%)
Jaundice	Often (30–79%)
Liver failure	Often (30–79%)
Micronodular cirrhosis	Often (30–79%)
Constipation	Sometimes (5–29%)
Scar tissue replaces healthy tissue in the liver	Sometimes (5–29%)
Abnormality of the liver	Rarely (1–4%)
Enlarged liver	Not recorded
Intermittent diarrhea	Not recorded
Intestinal perforation	Not recorded
Malabsorption	Not recorded
Malnutrition	Not recorded

Abnormality of the eye

Trait	How often it is seen
Cerebral visual impairment	Always
Double vision	Always
Drooping of both upper eyelids	Always
Drooping upper eyelid	Always
Inward turning cross eyed	Always
Progressive external ophthalmoplegia	Always
Weakness of muscles controlling eye movement	Always
Paralysis or weakness of muscles within or surrounding outer part of eye	Very often (80–99%)
Abnormality of eye movement	Often (30–79%)
Abnormality of the eye	Often (30–79%)
Abnormality of vision	Often (30–79%)
Eye muscle paralysis	Often (30–79%)
Gaze-evoked nystagmus	Often (30–79%)
Hemianopia	Often (30–79%)
Involuntary, rapid, rhythmic eye movements	Often (30–79%)
Optic atrophy	Often (30–79%)
Total ophthalmoplegia	Often (30–79%)
Upgaze palsy	Often (30–79%)
Blindness	Sometimes (5–29%)
Clouding of the lens of the eye	Sometimes (5–29%)
Color blindness	Sometimes (5–29%)
Optic neuritis	Sometimes (5–29%)
Retina issue	Sometimes (5–29%)
Retinal pigment epithelial mottling	Sometimes (5–29%)
Visual impairment	Sometimes (5–29%)
Abnormality of visual evoked potentials	Not recorded
Visual loss	Not recorded

Laboratory abnormality

Trait	How often it is seen
Elevated circulating deoxyuridine concentration	Always
Elevated circulating thymidine concentration	Always
Reduced tissue thymidine phosphorylase activity	Always
Anasarca	Often (30–79%)
High liver enzymes	Often (30–79%)
Higher than normal levels of lactate in blood	Often (30–79%)
Increased blood alanine	Often (30–79%)
Increased circulating pyruvate concentration	Often (30–79%)
Increased CSF protein concentration	Often (30–79%)
Increased lactate in body	Often (30–79%)
Elevated blood creatine phosphokinase	Sometimes (5–29%)
Glucose intolerance	Sometimes (5–29%)
Macrovesicular hepatic steatosis	Sometimes (5–29%)
Mildly elevated creatine kinase	Sometimes (5–29%)
Diabetes mellitus	Rarely (1–4%)
Fluid retention	Rarely (1–4%)
High levels of ketone bodies	Rarely (1–4%)
3-Methylglutaconic aciduria	Not recorded
Acidic urine	Not recorded
Ethylmalonic aciduria	Not recorded
Microvesicular hepatic steatosis	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Disease of the heart muscle	Often (30–79%)
Mitral valve prolapse	Often (30–79%)
ST segment elevation	Often (30–79%)
Abnormal heart rate	Sometimes (5–29%)
Left ventricular hypertrophy	Sometimes (5–29%)
Mitral regurgitation	Sometimes (5–29%)
Quivering upper heart chambers resulting in irregular heartbeat	Sometimes (5–29%)
Reduced left ventricular ejection fraction	Sometimes (5–29%)
Stretched and thinned heart muscle	Sometimes (5–29%)
Ventricular arrhythmia	Sometimes (5–29%)
Palpitations	Rarely (1–4%)

Abnormality of limbs

Trait	How often it is seen
Areflexia of lower limbs	Always
Abnormality of the hand	Often (30–79%)
Foot drop	Often (30–79%)
Limb muscle weakness	Often (30–79%)
Quadriceps weakness	Often (30–79%)
Weak shoulder muscles	Often (30–79%)
Absent ankle reflexes	Sometimes (5–29%)
Hand muscle weakness	Sometimes (5–29%)
High-arched foot	Sometimes (5–29%)
Winged shoulder blade	Sometimes (5–29%)

Abnormality of head or neck

Trait	How often it is seen
Bell's palsy	Always
Weakness of facial musculature	Always
Abnormality of the extraocular muscles	Often (30–79%)
Abnormally small head	Often (30–79%)
Decreased facial expressions	Often (30–79%)
Expressionless face	Often (30–79%)
Movement abnormality of the tongue	Often (30–79%)
Facial diplegia	Sometimes (5–29%)

Abnormal cellular phenotype

Trait	How often it is seen
Decreased activity of mitochondrial complex I	Always
Decreased activity of mitochondrial complex IV	Always
Depletion of mitochondrial DNA in muscle tissue	Always
Multiple mitochondrial DNA deletions	Always
Abnormality of the mitochondrion	Often (30–79%)
Abnormal cell morphology	Sometimes (5–29%)

Abnormality of the endocrine system

Trait	How often it is seen
Hashimoto thyroiditis	Often (30–79%)
Hypergonadotropic hypogonadism	Sometimes (5–29%)
Hypogonadotropic hypogonadism	Sometimes (5–29%)
Enlarged thyroid gland in neck	Rarely (1–4%)
Overactive thyroid	Rarely (1–4%)
Underactive thyroid	Rarely (1–4%)

Abnormality of the genitourinary system

Trait	How often it is seen
Previous menstrual periods stop	Always
Nocturia	Rarely (1–4%)
Early menopause	Not recorded
Primary amenorrhea	Not recorded
Testicular degeneration	Not recorded

Abnormality of the ear

Trait	How often it is seen
Sensorineural hearing impairment	Always
Abnormal vestibular function	Often (30–79%)
Bilateral sensorineural hearing impairment	Often (30–79%)
Hearing impairment	Sometimes (5–29%)

Abnormality of the respiratory system

Trait	How often it is seen
Floppy windpipe	Often (30–79%)
Slow breathing	Often (30–79%)
Exertional breathlessness	Sometimes (5–29%)
Respiratory function loss	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Allodynia	Always
Decreased ability to exercise	Always
Fatigue	Often (30–79%)
Muscle ache	Sometimes (5–29%)

Growth abnormality

Trait	How often it is seen
Wasting syndrome	Always
Weight loss	Always
Faltering weight	Sometimes (5–29%)
Slender build	Not recorded

Abnormality of the voice

Trait	How often it is seen
Nasal speech	Sometimes (5–29%)
Weak voice	Sometimes (5–29%)
Inability to produce voice sounds	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Low number of red blood cells or hemoglobin	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 POLG and how often each is seen. Find out more at hpo.jax.org.

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