Mitochondrial diseases comprise those disorders that in one way or another affect the function of the mitochondria or are due to mitochondrial DNA. Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. The subclass of these diseases that have neuromuscular disease symptoms are often referred to as a mitochondrial myopathy.
In addition to the Mitochondrial myopathies, other examples include:
• Diabetes mellitus and deafness (DAD)
o this combination at an early age can be due to mitochondrial disease
o Diabetes mellitus and deafness can also be found together for other reasons
• Leber's hereditary optic neuropathy (LHON)
o visual loss beginning in young adulthood
o eye disorder characterized by progressive loss of central vision due to degeneration of the optic nerves and retina
o Wolff-Parkinson-White syndrome
o multiple sclerosis-type disease
o affects 1 in 50,000 people in Finland
• Leigh syndrome, subacute sclerosing encephalopathy
o after normal development the disease usually begins late in the first year of life, although onset may occur in adulthood
o a rapid decline in function occurs and is marked by seizures, altered states of consciousness, dementia, ventilatory failure
• Neuropathy, ataxia, retinitis pigmentosa, and ptosis (NARP)
o progressive symptoms as described in the acronym
o dementia
• Myoneurogenic gastrointestinal encephalopathy (MNGIE)
o gastrointestinal pseudo-obstruction
o neuropathy
• Myoclonic Epilepsy with Ragged Red Fibers (MERRF)
o progressive myoclonic epilepsy
o "Ragged Red Fibers" - clumps of diseased mitochondria accumulate in the subsarcolemmal region of the muscle fiber and appear as "Ragged Red Fibers" when muscle is stained with modified Gömöri trichrome stain
o short stature
o hearing loss
o lactic acidosis
o exercise intolerance
• Mitochondrial myopathy, encephalomyopathy, lactic acidosis, stroke-like symptoms (MELAS)
