[http://youtu.be/txTdcqDTL9E] (YouTube link)Twelve...  ...utu.be/txTdcqDTL9E] (YouTube link)Twelve-year-old McKenzie Carey (warning: autoplay music) suffers from mitochondr...  ...ars. “We were told it would be a miracle if McKenzie made it to age 5,” Tammy says. McKenzie...