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Health condition

POLG-related disease

POLG gene defects disrupt mitochondrial DNA maintenance, producing a remarkable range of conditions from epilepsy and ataxia to eye movement failure - with one absolute drug rule: avoid valproate.

Key points

What matters most, at a glance.

The essentials in plain English - symptoms, when to seek help, who to see and what treatment looks like.

  • One gene, many syndromes: severe childhood epilepsy (Alpers), adolescent-adult ataxia-neuropathy, and adult CPEO with weakness

  • Common adult picture: sensory neuropathy, ataxia, eye movement limitation, epilepsy and migraine in combination

  • Sodium valproate can trigger fatal liver failure in POLG disease - it must be avoided when POLG is suspected

  • Occipital-onset seizures and epilepsia partialis continua are characteristic epilepsy patterns

  • Diagnosis is by POLG gene sequencing; carrier frequency makes it a common cause of recessive mitochondrial disease

  • Management is multidisciplinary with specific attention to epilepsy drug choice and liver monitoring

Understanding it

About POLG-related disease, and what to do next.

POLG encodes the enzyme that replicates mitochondrial DNA; when it falters, mtDNA depletes or accumulates errors, and disease surfaces wherever energy demand bites. The phenotypes cluster by age: infants and children with Alpers syndrome (epilepsy, liver failure, regression); teenagers and young adults with sensory ataxic neuropathy, ophthalmoplegia and often stubborn occipital epilepsy; older adults with CPEO-plus pictures. Between these anchor points lie blends, which is why POLG sequencing has become a routine reflex in unexplained ataxia, refractory epilepsy with the right flavour, and any mitochondrial-looking syndrome.

One pharmacological fact towers over the rest: valproate can precipitate irreversible, often fatal hepatotoxicity in POLG disease, so the drug is contraindicated once POLG is suspected - and worth screening for before valproate in young patients with suggestive epilepsy. Otherwise care is assembled per patient: epilepsy management favouring levetiracetam and similar agents, neuropathy and ataxia rehabilitation, swallowing and nutrition support, and family counselling around recessive (occasionally dominant) inheritance. Specialist mitochondrial centres hold the experience for the difficult decisions, including status epilepticus protocols, and referral is appropriate at diagnosis rather than crisis.

A quiet reminder

This guide is for information, not medical advice.

Your GP knows your history and can tell you which parts apply to you. If in doubt, see them.

Frequently asked

Common questions about POLG-related disease.

Quick, plain-English answers to what people ask us most.

  • What is POLG-related disease?

    POLG-related disease refers to a group of inherited conditions caused by mutations in the POLG gene, which is essential for maintaining mitochondrial DNA, leading to a range of neurological and other symptoms depending on the specific mutation and severity.

  • What causes POLG-related disease?

    It's caused by inherited mutations in the POLG gene, which disrupt the normal maintenance and repair of mitochondrial DNA, the genetic material within the energy-producing structures of cells.

  • What are the symptoms?

    Symptoms vary widely depending on the specific POLG mutation and age of onset, and can include seizures, muscle weakness, loss of coordination, vision and hearing problems, and liver dysfunction.

  • Is POLG-related disease serious?

    Yes, particularly the earlier-onset, more severe forms, which can be life-limiting; milder, later-onset forms tend to progress more slowly, but the condition is generally serious and requires specialist management.

  • Is POLG-related disease hereditary?

    Yes, it's an inherited genetic condition, typically passed on in an autosomal recessive pattern, meaning both parents usually carry one copy of a faulty gene without being affected themselves.

  • Can POLG-related disease be treated?

    There's no cure currently, and treatment focuses on managing specific symptoms, such as anti-seizure medication, physiotherapy, and supportive care, alongside avoiding certain medications known to worsen the condition, such as valproate.

  • How is POLG-related disease diagnosed?

    Genetic testing confirming mutations in the POLG gene establishes the diagnosis, often prompted by a combination of clinical features and, sometimes, muscle biopsy findings suggestive of mitochondrial disease.

  • How does the disease progress over time?

    Progression varies significantly depending on the specific mutations and age of onset, with earlier-onset forms typically progressing more rapidly than later-onset forms; regular specialist follow-up helps track and manage changes.

  • POLG-related disease vs other mitochondrial diseases — what's the difference?

    Many different genes can cause mitochondrial disease, each with somewhat different patterns of symptoms and inheritance; POLG mutations specifically affect mitochondrial DNA maintenance, which genetic testing can confirm and distinguish from other mitochondrial gene mutations.

  • When should I see a specialist, and how quickly can I be seen privately?

    See a neurologist or specialist in mitochondrial disease if there are relevant symptoms, particularly with a family history. Private specialist and genetic assessment is typically available within about two weeks, faster than standard NHS pathways for rare disease referral.