MPV17-related hepatocerebral mitochondrial DNA depletion syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

MPV17-related hepatocerebral mitochondrial DNA depletion syndrome is an inherited disorder that can cause liver disease and neurological problems. The signs and symptoms of this condition begin in infancy and typically include vomiting, diarrhea, and an inability to grow or gain weight at the expected rate (faltering weight). Many affected infants have a buildup of a chemical called lactic acid in the body (lactic acidosis) and low blood glucose (hypoglycemia). Within the first weeks of life, infants develop liver disease that quickly progresses to liver failure. The liver is frequently enlarged (hepatomegaly) and liver cells often have a reduced ability to release a digestive fluid called bile (cholestasis). Rarely, affected children develop liver cancer. After the onset of liver disease, many affected infants develop neurological problems, which can include developmental delay, weak muscle tone (hypotonia), and reduced sensation in the limbs (peripheral neuropathy). Individuals with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome typically survive only into infancy or early childhood.

MPV17-related hepatocerebral mitochondrial DNA depletion syndrome is most frequently seen in the Navajo population of the southwestern United States. In this population, the condition is known as Navajo neurohepatopathy. People with Navajo neurohepatopathy tend to have a longer life expectancy than those with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. In addition to the signs and symptoms described above, people with Navajo neurohepatopathy may have problems with sensing pain that can lead to painless bone fractures and self-mutilation of the fingers or toes. Individuals with Navajo neurohepatopathy may lack feeling in the clear front covering of the eye (corneal anesthesia), which can lead to open sores and scarring on the cornea, resulting in impaired vision. The cause of these additional features is unknown.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

As the condition name suggests, mutations in the MPV17 gene cause MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. The protein produced from the MPV17 gene is located in the inner membrane of cell structures called mitochondria. Mitochondria are involved in a wide variety of cellular activities, including energy production, chemical signaling, and regulation of cell growth, division, and death. Mitochondria contain their own DNA, known as mitochondrial DNA (mtDNA), which is essential for the normal function of these structures. It is likely that the MPV17 protein is involved in the maintenance of mtDNA. Having an adequate amount of mtDNA is essential for normal energy production within cells.

MPV17 gene mutations that cause MPV17-related hepatocerebral mitochondrial DNA depletion syndrome lead to production of a protein with impaired function. One mutation causes all cases of Navajo neurohepatopathy and results in the production of an unstable MPV17 protein that is quickly broken down. A dysfunctional or absent MPV17 protein leads to problems with the maintenance of mtDNA, which can cause a reduction in the amount of mtDNA (known as mitochondrial DNA depletion). Mitochondrial DNA depletion impairs mitochondrial function in many of the body's cells and tissues, particularly the brain, liver, and other tissues that have high energy requirements. Reduced mitochondrial function in the liver and brain lead to the liver failure and neurological dysfunction associated with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. Researchers suggest that the less mtDNA that is available in cells, the more severe the features of Navajo neurohepatopathy.

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

MPV17-related hepatocerebral mitochondrial DNA depletion syndrome is thought to be a rare condition. Approximately 30 cases have been described in the scientific literature, including seven families with Navajo neurohepatopathy. Within the Navajo Nation of the southwestern United States, Navajo neurohepatopathy is estimated to occur in 1 in 1,600 newborns.

Which doctor should you see?

The suggested department for discussing MPV17-related hepatocerebral mitochondrial DNA depletion syndrome 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 MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. 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.