Hereditary Spastic Paraplegia (HSP) comprises a group of rare, inherited neurological disorders characterized by progressive spasticity and weakness in the leg and hip muscles. Approximately 30 different types of HSP have been identified, with the genetic causes known for eleven of them. In the United States, the incidence rate of HSP is estimated to be around 20,000 people.
The primary feature of HSP is the gradual onset of difficulty walking due to increasing stiffness and weakness in the leg muscles. Symptoms typically manifest between the second and fourth decades of life but can begin at any age.
Initial symptoms often include problems with balance, toe-stubbing, or stumbling, with changes occurring so gradually that they may be noticed by others before being recognized by the affected individual. As the disease progresses, assistive devices such as canes, walkers, and wheelchairs may be required, although some individuals may never need such aids.
Common symptoms of HSP include urinary urgency and frequency, hyperactive reflexes, difficulty with balance, clonus, Babinski’s sign, reduced vibration sense in the feet, muscle spasms, and congenital foot abnormalities like pes cavus (high-arched foot). While some individuals may experience issues with their arms or fine motor control of their fingers, these symptoms are generally not prominent.
Most individuals with HSP have uncomplicated forms of the condition. However, there are rare, complicated forms that present with additional symptoms such as peripheral neuropathy, ichthyosis (a skin disorder), epilepsy, ataxia, optic neuropathy, retinopathy, dementia, mental retardation, deafness, or problems with speech, swallowing, or breathing. It is important to note that these additional symptoms may be caused by factors unrelated to HSP, such as diabetes-induced peripheral neuropathy.