FOP or Fibrodysplasia Ossificans Progressiva is the rarest of rare genetic medical condition.
It is a sort of genetic skeletal disorder where muscles and tissues of the body gets turned into bone.
In FOP, mobility is restricted as the bone formed from muscles affects joints locking them either partially or completely. And as the last word in Fibrodysplasia Ossificans Progressiva suggests, it is a progressive disease. That is, the disease progresses with age.
So far there are only about 2,500 known cases for this disease all over the world.