Osteopetrosis is a rare genetic disease found on the X chromosome and it effects the development of the bones. Most people with this disease are born with it and unfortunately die at an early age because of it, but some adults have been known to develop it too. 

 

The logo is an initial hand drawing of the two arm bones and two leg bones made to look like an X-ray. You can see from the logo development that the green x-ray colours were replaced with a more multi-coloured logo so that it wouldn't look too serious or scary for children.