Mitochondrial complex I deficiency

What is the long-term outlook for people with mitochondrial complex I deficiency?

There can be a lot of variability in the signs, symptoms and severity for people with mitochondrial complex I deficiency. Therefore, the long-term outlook (prognosis) varies among affected people.

In isolated complex I deficiency, the majority of affected people develop symptoms during the first year of life. Most people with this type have a rapidly progressive disease course and do not survive beyond childhood.

In other cases, signs and symptoms can range, causing an affected person to have any of the following:

  • fatal neonatal lactic acidosis - this is typically rapidly progressive, resulting in death in infancy
  • infantile-onset Leigh syndrome - affected children typically have normal early development but develop symptoms in late infancy or early childhood with progressive neurological abnormalities
  • childhood-onset mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome - symptoms usually begin in childhood with seizures, migraines, vomiting, exercise intolerance, proximal limb weakness and short stature
  • adult-onset syndromes of encephalomyopathy (brain and muscle disease) with variable severity

There have also been some affected people who have had involvement of only one organ (for example, isolated hypertrophic cardiomyopathy (HCM) or Leber hereditary optic neuropathy).

Because not all people with this condition are affected the same way, the life expectancy may differ considerably.

Last updated on 05-01-20

Name: MitoAction PO Box 51474
Boston, MA, 02205, United States
Phone: 1-888-MITO-411 (648-6411) for support line Toll Free: 1-888-648-6228 Email: Url:
Name: United Mitochondrial Disease Foundation 8085 Saltsburg Road, Suite 201
Pittsburgh, PA, 15239 , United States
Phone: +1-412-793-8077 Toll Free: 1-888-317-8633 Fax : +1-412-793-6477 Email: Url:

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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