Physical Strategies points to the story of Michigan's Liam Hoekstra, born with the incredibly rare condition myostatin-related muscle hypertrophy; or muscle enlargement. Quite simply, this kid is ripped - at 19 months.
Although there are no known side effects (aside from an accelerated metabolism, and the accompanying grocery bills); this rare state does hold plenty of promise for various muscle-wasting conditions such as muscular dystrophy. The next 5 years will be very interesting indeed.