Combined oxidative phosphorylation deficiency 1

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Combined oxidative phosphorylation deficiency 1 is a severe condition that primarily impairs neurological and liver function.

Most people with combined oxidative phosphorylation deficiency 1 have severe brain dysfunction (encephalopathy) that worsens over time; they also have difficulty growing and gaining weight at the expected rate (faltering weight). In some cases, affected individuals have abnormal muscle tone (increased or decreased), developmental delay, seizures, loss of sensation in the limbs (peripheral neuropathy), and an unusually small head (microcephaly). Liver disease is common in people with combined oxidative phosphorylation deficiency 1, with individuals quickly developing liver failure. Individuals with this condition also usually have a potentially life-threatening buildup of a chemical called lactic acid in the body (lactic acidosis).

The neurological features of combined oxidative phosphorylation deficiency 1 are largely due to brain abnormalities that include thinning of the tissue that connects the two halves of the brain (corpus callosum hypoplasia) and loss of brain tissue called white matter (leukodystrophy), particularly in an area of the brain called the basal ganglia, which normally helps control movement.

Individuals with combined oxidative phosphorylation deficiency 1 usually do not survive past early childhood, although some people live longer.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Combined oxidative phosphorylation deficiency 1 is caused by mutations in the GFM1 gene. This gene provides instructions for making an enzyme called mitochondrial translation elongation factor G1. This enzyme is found in cell structures called mitochondria, which are the energy-producing centers in cells.

While instructions for making most of the body's proteins are found in DNA that is stored in the nucleus of cells (nuclear DNA), a few proteins and other molecules are produced from DNA that is stored in mitochondria (mtDNA). Mitochondrial translation elongation factor G1 is involved in the production of proteins from mtDNA genes through a process called translation. The enzyme's role in translation is to coordinate the movements of mtRNA molecules, which are the protein blueprints created from mtDNA. This function allows assembly of proteins to continue until it is complete. Genes on mtDNA provide instructions for proteins that are primarily involved in the process of converting the energy from food into a form cells can use (oxidative phosphorylation).

GFM1 gene mutations reduce or eliminate mitochondrial translation elongation factor G1 function. As a result, fewer mitochondrial proteins involved in oxidative phosphorylation are produced. (The process of oxidative phosphorylation involves five groups of proteins, or complexes. The condition is called combined oxidative phosphorylation deficiency 1 because it impairs the function of more than one of these complexes.) Organs that have high energy demands, such as the brain and liver, are particularly affected by the resulting impairment of oxidative phosphorylation. A shortage of energy in these tissues leads to cell death, causing the neurological and liver problems in people with combined oxidative phosphorylation deficiency 1. It is thought that other tissues that require a lot of energy, such as the heart and other muscles, are not affected in this condition because they have additional enzymes that can perform the process of mitochondrial protein production.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Combined oxidative phosphorylation deficiency 1 is likely a rare disorder, although its prevalence is unknown. At least 12 affected individuals have been described in the scientific literature.

Which doctor should you see?

The suggested department for discussing Combined oxidative phosphorylation deficiency 1 is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Combined oxidative phosphorylation deficiency 1. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.