Successive stressors on the body can lead to a stepwise reduction in the number of mitochondria per cell in select organs. Over time this can lead to conditions like chronic fatigue and fibromyalgia due to lower energy generation and premature senescence. In each patient the severity of dysfunction can vary in each organ system partly based on heteroplasmy.
Based on the genetic features of the mitochondrial mix within each organ, that organ has a degree of tolerance for toxic and infectious stressors. Once it is past that threshold then mitochondria begin to fail to produce enough energy to keep up with demand. That is when symptoms of fatigue or more organ specific symptoms begin to appear. This is when senescence begins.
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