Mitochondrial Disorders

Mitochondrial disorders are suspected to be the underlying cause of infantile spasms for a substantial portion of patients. However, the diagnosis and treatment of this group of disorders is very challenging.

Mitochondria are the "powerplants" of our bodies' cells and are found in great abundance within the cells of the brain, nerves, eyes, muscle, heart, liver, and kidneys. As such, mitochondrial disorders represent a large and diverse family of related disorders, associated with a ever-growing list of mutations in genes important for normal function of the mitochondria. The symptoms of mitochondrial disease are quite variable (even among patients with the same genetic mutation) but commonly include seizures, cognitive dysfunction, vision impairment or problems with eye movements, low muscle tone, hearing impairment, and short stature. Most patients do not exhibit all of these symptoms, and there are numerous patients with symptoms other than those listed above. Some mitochondrial disorders have fairly typical symptom patterns and are known by specific names, such as Leigh disease. However,  there any many different genetic abnormalities associated with each "named" mitochondrial disorder. 

There are many ways to test for mitochondrial disorders, including calculation of the ratio of lactate to pyruvate in blood and cerebrospinal fluid (CSF), mitochondrial DNA mutation panels (most useful when a specific "named" mitochondrial syndrome is suspected), muscle biopsy (to allow direct microscopic visualization and other testing of mitochondria), functional testing of specific mitochondrial enzymes, whole exome sequencing (see summary in genetic testing), as well as sequencing of either individual mitochondrial genes or the entire mitochondrial genome. 

For the vast majority of mitochondrial disorders, treatment options are tailored to specific symptoms (e.g. anti-seizure medications for infantile spasms) rather than a "cure", though this is an avenue of active scientific investigation. A variety of supplements and vitamins have been recommended to aid mitochondrial function, such as coenzyme Q10, levocarnitine, several B vitamins, and various antioxidants. These supplements generally have limited efficacy. In addition, there are a variety of dietary changes which can be beneficial in specific disorders such as avoidance of fasting, reduction in fat intake (although many patients benefit from increased intake of specific types of fat). Furthermore, the ketogenic diet can be very effective for treating seizures among some patients with mitochondrial diorders, and conversely, very dangerous for other patients with mitochondrial disorders. Any patient with known or suspected mitochondrial dysfunction should undergo careful metabolic testing prior to beginning the ketogenic diet. Lastly, it is important to avoid substances which can be toxic to mitochondria such as valproic acid (Depakote® or Depakene®) and excessive iron supplements.

For additional information, please see the United Mitochondrial Foundation Website.


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