Hereditary spastic paraplegia (HSP) is a condition where a person's muscles in the legs become very stiff and hard to move. This happens because of a special kind of gene that they get from their parents.
Imagine that you have a special puzzle piece in your body that tells your legs how to move. If you have HSP, your puzzle piece isn't quite right, and your legs become very stiff and hard to move. This can make it really difficult to walk or move around.
HSP is called "hereditary" because it is passed down from parents to their children. If one of your parents has HSP, you have a 50% chance of inheriting the gene and developing the condition, too.
Sometimes HSP can be mild, so people with the condition may be able to walk without too much difficulty. Other times it can be more severe and make it hard to move around at all.
Luckily, doctors and scientists are working on ways to help people with HSP. They may give you special exercises or medicine to help with stiffness. In really severe cases, they may even consider surgery to help with movement.