Mitochondrial DNA Depletion Syndrome (MDDS)


Fact: Transmission is likely to be linked to maternal mitochondrial DNA and there is no cure!

What is MDDS?
Mitochondrial DNA depletion syndrome (MDS or MDDS): one of a number of diseases characterized by a decrease in the amount of mitochondrial DNA in affected body tissues. Mitochondria are structures within cells that are important for converting food into an energy form that cells can use, and they contain a small amount of DNA, although most of a cell's DNA resides within its nucleus.

MDDS condition are genetic (inherited) and are passed to offspring in an autosomal recessive manner. The condition is usually fatal in infancy.

Different forms of the condition affect the muscles (myopathic form), the liver (hepatopathic), or the or both the muscles and brain (encephalomyopathic). The condition gained much public attention in 2017 due to media reports of a boy named Charlie Gard born with the condition in the UK.


Mitochondrial Disease
Mitochondrial disease is an inherited chronic illness that can be present at birth or develop later in life. It causes debilitating physical, developmental, and cognitive disabilities with symptoms including poor growth; loss of muscle coordination; muscle weakness and pain; seizures; vision and/or hearing loss; gastrointestinal issues; learning disabilities; and organ failure. It is estimated that 1 in 4,000 people has Mito.  It's progressive and there is no cure.

What are Mitochondria?

  • Mitochondria are tiny organelles found in almost every cell in the body.
  • They are known as the "powerhouse of the cell."
  • They are responsible for creating more than 90 percent of cellular energy.
  • They are necessary in the body to sustain life and support growth.
  • They are composed of tiny packages of enzymes that turn nutrients into cellular energy.
  • Mitochondrial failure causes cell injury that leads to cell death. When multiple organ cells die there is organ failure.


What are the Symptoms of Mitochondrial Disease?The severity of mitochondrial disease symptoms is different from person to person. The most common symptoms are:

  • Poor growth
  • Loss of muscle coordination, muscle weakness
  • Neurological problems, seizures
  • Autism, autistic spectrum, autistic-like features
  • Visual and/or hearing problems
  • Developmental delays, learning disabilities
  • Heart, liver or kidney disease
  • Gastrointestinal disorders, severe constipation
  • Diabetes
  • Increased risk of infection
  • Thyroid and/or adrenal dysfunction
  • Autonomic dysfunction
  • Neuropsychological changes characterized by confusion, disorientation, and memory loss.

How common are mitochondrial diseases?

  • Infants, children, and adults may develop mitochondrial disorders. Experts in mitochondrial medicine agree there is a spectrum of the disease, ranging from mild to severe.
  • In adults, many diseases of aging have been found to have defects of mitochondrial function; these include, but are not limited to, Type 2 diabetes, Parkinson's disease, atherosclerotic heart disease, stroke, Alzheimer's disease, and cancer. In addition, many medicines can injure the mitochondria.


What causes mitochondrial disease?For many patients, mitochondrial disease is an inherited genetic condition. An uncertain percentage of patients acquire symptoms due to other factors, including mitochondrial toxins.
It is important to determine which type of mitochondrial disease inheritance is present in order to predict the risk of recurrence for future children. The types of mitochondrial disease inheritance include:

  • DNA (DNA contained in the nucleus of the cell) inheritance. Also called autosomal inheritance.
    • If this gene trait is recessive (one gene from each parent), often no other family members appear to be affected. There is a 25 percent chance of the trait occurring in other siblings.
    • If this gene trait is dominant (a gene from either parent), the disease often occurs in other family members. There is a 50 percent chance of the trait occurring in other siblings.

MtDNA (DNA contained in the mitochondria) inheritance.

  • There is a 100 percent chance of the trait occurring in other siblings, since all mitochondria are inherited from the mother, although symptoms might be either more or less severe.

Combination of mtDNA and nDNA defects:

  • Relationship between nDNA and mtDNA and their correlation in mitochondrial formation is unknown.

Random occurrences

  • Diseases specifically from deletions of large parts of the mitochondrial DNA molecule are usually sporadic without affecting other family member.
  • Medicines or other toxic substances can trigger mitochondrial disease.


How is Mitochondrial Disease Diagnosed?

  • There is no reliable and consistent means of diagnosis.
  • Diagnosis can be made by one of the few physicians who specialize in mitochondrial disease.
  • Diagnosis can be made by blood DNA testing and/or muscle biopsy but neither of these tests is completely reliable

How is Mitochondrial Disease Treated?The goal is to improve symptoms and slow progression of the disease.

  • Use vitamin therapy
  • Conserve energy
  • Pace activities
  • Maintain an ambient environmental temperature
  • Avoid exposure to illness
  • Ensure adequate nutrition and hydration


Misdiagnosis

  • Lack of understanding of the disease and misinterpretation of symptoms can lead to misdiagnosis.
  • Further progression of symptoms can occur if the symptoms are missed and opportunities for treatment and support are not recognized.


What are the Challenges of Living with Mitochondrial Disease?

  • Affects multiple organs, affects multiple family members, affects multiple generations.
  • Lack of awareness and understanding of the disease.
  • Families are continuously forced to expend their very limited energy to explain their disease, advocate for themselves and fight for services.
  • Mitochondrial disease is often an "invisible disease."
    • Good day - Patients look fine and healthy. They have more energy and appear rested.
    • Bad day - - Patients appear tired to significantly ill. They are obviously fatigued and/or have significant illness. Repeated "bad days"often lead to decompensation and patients have difficulty returning to baseline.
  • Mitochondrial disease is unpredictable. Day to day, hour to hour patients can develop symptoms and their stability can be threatened.
  • Difficulties establishing a diagnosis interfere with a patient's ability to obtain adequate recognition, medical care, insurance coverage, healthcare supports, and disability services.
  • Lack of understanding of the disease and misinterpretation of symptoms can lead to misdiagnosis. Further progression of symptoms can occur if the symptoms are missed and opportunities for treatment and support are not recognized.
  • An individual can become symptomatic at any time in life despite the fact that it is inherited.
  • It is difficult to diagnose.


What is the Prognosis for Someone?

  • The prognosis is variable. Some people live a normal life and are minimally affected; others can be severely compromised with the disease.
  • It is completely individualized.
  • The prognosis is unpredictable

Want to learn more?
The following are organizations and/or websites dedicated to providing information and education surrounding 
Mitochondrial DNA Depletion Syndrome (MDDS). These organizations are dedicated to research, education, awareness, and/or support. They are listed in Alphabetical order without any preference or prejudice. Listing these organizations is not a recommendation or referral in any regard for seeking treatment or consultation or support for treatment.


Blueprint Genetics
OMIM
Medicinenet.com
MitoAction
NIH
Springer Link

Information on this page taken directly from:
MitoAction
NIH