Hereditary spastic paraplegia is a general term for a group of rare inherited disorders that cause weakness and stiffness in the leg muscles. ... It's difficult to know exactly how many people have hereditary spastic paraplegia because it's often misdiagnosed. Estimates range from 1 in 11,000 people to 1 in 77,000 people
People with spastic paraplegia type 49 can develop recurrent episodes of severe weakness, hypotonia, and abnormal breathing, which can be life threatening.