Overview

A mitochondrion is a tiny organelle that lives inside every gentic material containing cell in the body. It acts as "power plant" of the cell by processing food and oxygen and changing them into energy so the cells themselves can do what cells do.

Sometimes, this goes wrong. As mitochondria are passed on down the female line, often, already damaged mtDNA (mitochondrial DNA) is passed down from a mother to her child - indeed, the chances of a mother with mitochondria disease caused by mutations in mtDNA not passing her disease on to her children is not, for every day purposes, different to zero (this number is not exactly zero, but as close as makes any difference). Occasionally, mtDNA mutates for some other reason. As mitochondria are normally protected from free radicals, they lack the repair mechanisms of nDNA (nuclear DNA - the normal stuff) and as a result, cannot repair the damage. As with all mutation, occasionally, they are neutral (that is, have no effect), even more rarely, they are actually positive, but as sheer probability dictates, most are deletrious - "however many ways there are of being alive, there are alomost infinitely more ways of being dead". This is when the problems begin.

Not all mitochondrion genes are encoded from mtDNA, indeed, only a small number are. Only ~13 proteins are coded for in mtDNA itself. The rest is contained in nDNA, and is inherited in the same manner as normal, nuclear DNA. However, whether the mutation causing mitochondrial disease is due to a mutation in mtDNA or nDNA does not matter - the result is the same.

When something goes wrong with mitochondria they become unable to process food and oxygen correctly. This leaves bits of unburned food behind which over time become toxic. This toxicity causes a positive feedback loop. That is, the increased toxicity leads to an increase in mutation or damage to mitochondria, which leads to them being even less able to do their jobs, which leads to more unburned food, more toxicity, and more mutation/damage, which leads to mitochondria being even less able to do their job, and so on and so forth.

That's all well and good, but nobody other than the geeks among us really cares what happens at the cellular level - you want to know what happens to patients. In a nutshell, if your mitochondria doesn't work, the cells they find themselves in don't work. If your cells don't work, the organs they find themselves in don't work. This can manifest itself as dementia with mitochondrial diseases in the brain, blindness in mitochondrial diseases in the eye, exercise intollerance in mitochondrial diseases in the muscles, etc

Symptoms

There is no single mitochondria disease. Rather, there are several (around 40 presently distinguished) different mitochondrial diseases. What they all have in common is the cellular activity explained above. Mitochondrial diseses can, in principle, effect any organ in the body, though some are more common than others.

All this makes it terribly difficult to offer symptoms. Again if you have mitochondria disease in an organ, the organ doesn't work properly. If you have mitochondria disease in your muscles, you may suffer fatigue, or "exercise intolerance". If you have mitochondria disease in your brain, you may suffer mental retardation, dementia, confusion, or any manner of neurological defect. Many resources offer symptoms of mitochondrial disease. Exercise intollerance appears to be a red flag in mitochondrial disease diagnosis, however, since mitochondrial diseases can manifest themselves with "any symptom, any time" we shan't offer a list of symptoms here. If you have specific symptoms and would like to know if they could be caused my mitochondria disease, stop by the forum and ask, or read more about diagnosis below.

Statistics on mitochondrial diseases are not easy to find. Mitochodondria disease can range right the way through from insignificant to utterly debilitating and many of the milder cases never get diagnosed at all. UK statistics are of poor quality, as sample sizes have always been too small and meta-analysis has never been performed. US statistics, however, show that somewhere in the region of one in 4,000 children will develop mitochondrial disease by the age of ten. In addition, around the same number are born with the disease. In adults, it gets even more confusing, as normal senescence (ageing) debilitates mitochondria too, bringing the total incidence of mitochondrial diseases by the time of senescence to 100%. Well known mitochondria senescence related diseases include Parkinsons, strokes, alezheimers, cancer and type 2 diabetes.

Diagnosis And Treatment

Mitochondrial diseases are so far and wide ranging that they can present themselves as pretty much anything, which makes diagnosis exceedingly difficult.

There is, of course, a method of diagnosis, but this is complicated, and difficult to summarise for non-professionals. This file from UMDF offers a good details, but is aimed at professionals.

It is difficult to summarise diagnosis without over simplification, but nevertheless, we shall try.

A huge problem with diagnosis, is it is expensive, and time consuming. This means many doctors are reluctant to test before ruling out everything else. Usually, once you have convinced your doctor to run the test, you will be taken into a clinic and have a series of tests of a period of days. The initial consideration is a patients family history. This is simply because most mitochondrial diseases are inherited, and so we should expect to find more incidence within a patients family. After this, you're likely to be given a full physical as well as a metabolic and neurological examination. These all serve two purposes - firstly to rule out any other causes of your symptoms, and secondly, to evaluate their severity. Following from this, further tests depend on your specific symptoms. DNA testing is often used, as are ECGs, MRIs and electoretinograms. Occasionally, we may need more invasive test like biopsies, as determined by your doctor.

There is no cure for any mitochondrial disease. Some things that can help in some patients include Coenzyme Q10, thiamine, riboflavin, niacin (B3), biotin, lipoic acid, selinium, various antioxidants and a good, old fashioned, civilised cup of tea (due to it's anti-oxidant properties)!

Several lines of research are presently being undertaken into cure and therapy. Antioxidant treatment looks promising, but is some way away. Arguably, the most promising of all lay with MitoSENS who produced arguably the most promising paper of all time relating to mitochondria disease, however, this is only useful in mitochondrial diseases caused by mutations to mtDNA.