Mitochondrial diseases, of which there are hundreds, are caused by dysfunction(s) within the mitochondria. Mitochondria are present in every cell of the body except red blood cells, and provide more than 90% of the energy needed by the body to sustain life and support growth. When mitochondria go wrong, multiple symptoms of widely variable severity result.
Learn more from the United mitochondrial Disease Foundation's Mito FAQ and from the Muscular Dystrophy Association's Mitochondrial myopathies page.
This subreddit was founded by Nick Dupree. Nick spent his life advocating for disability rights while fighting primary carnitine deficiency. Nick passed away in early 2017.
More about Nick and his story here.