Rare diseases, as the name indicates, only affect a small part of the population. However, for those affected they are particularly challenging, often especially because research into such rare diseases tends to be less of a priority. One of these diseases is hereditary spastic paraplegia (HSP), a disease that causes spasms and weakness in the leg muscles, increasingly affecting mobility as the disease progresses. Approximately 77,000 people across Europe suffer from the condition. Researchers have already discovered that the disease starts in nerve cells in the brain. These are obviously particularly difficult to investigate.