Just because of some of the symptoms people have been talking about here, I thought I'd mention another disorder I just heard about compliments of a post on a 23andme fibromyalgia forum. Note if you go to this link immediately below, you'll see a bunch of other muscular disorders mentioned on the right side as well.
http://mda.org/disease/metabolic-dis...ase-deficiency
What are the symptoms of myoadenylate deaminase deficiency?
The disease may cause exercise intolerance, cramps and muscle pain; although, in many cases, people with deficiencies in this enzyme may experience no symptoms.
------
There is a specific SNP (gene mutation) involved in this disorder as well. If you've tested with 23andme, the currently last post on this page will give you easy access to checking for your status on this SNP. The SNPedia page gives a lot more information on the SNP and some confusion surrounding it.
https://www.23andme.com/you/communit...681/last_page/
http://www.snpedia.com/index.php/Rs17602729