This horrifying condition was first documented when a former astronaut, misdiagnosed with restless leg syndrome, woke to find his arm detached and crawling around the room. Walking Limb Disease is believed to have come from alien pathogens picked up somewhere on the astronaut's travels but its exact place of origin has yet to be discovered. Once infected the symptoms are quite similar to restless leg syndrome until of course your afflicted limb detaches. The creature must gestate for several months before it is capable of detaching and surviving on its own, once it detaches it will continue to mutate to better suit its survival. Walking limb disease can affect both arms and legs, but thankfully there have only been a handful of cases...so far.