Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis, is a group of rare and progressive inherited disorders that cause weakness and stiffness of the legs (spasticity). There are more than 80 genetic types of HSP. Early on, people may have some trouble walking and feel some stiffness. Over time, these symptoms usually get worse. Many people with HSP eventually need a cane, walker, or wheelchair.

The main signs of typical HSP are progressive leg stiffness and weakness. Most people with HSP have the “pure” or “uncomplicated” type, where spasticity and muscle weakness are the main symptoms. About 10% of people with HSP have what’s called complicated HSP and may have additional neurological symptoms. In complicated forms of HSP, people may also experience:

• Vision problems caused by cataracts or damage to the optic nerve and retina
• Poor muscle coordination (ataxia)
• Seizures (epilepsy)
• Trouble with thinking and memory (cognitive impairment)
• Nerve damage outside the brain and spinal cord (peripheral neuropathy)
• Hearing loss (deafness)

Troyer syndrome is one example of HSP. Troyer syndrome is caused by a variation in the SPGP20 gene located on chromosome 13. Troyer syndrome is an autosomal recessive disorder, which means that both parents must carry and pass on the defective gene for the child to be affected. In addition to muscle weakness and spasms in the legs, other symptoms of Troyer syndrome include:

• Permanent shortening of one or both legs
• Difficulty walking
• Speech disorders
• Drooling
• Weakening of the hand muscles
• Developmental delays
• Mood changes
• Short stature

HSP affects the nervous system by damaging the long nerve pathways that carry movement signals from the brain to the muscles, especially the legs. As these pathways become damaged over time, it becomes harder for the brain to send the right signals for smooth, controlled movement. This can lead to stiffness, muscle tightness, weakness, balance problems, and difficulty walking. Because the pathways to the legs are some of the longest in the body, the legs are usually affected the most. In some forms of HSP, other parts of the body can also be affected, which may lead to additional challenges with the arms, speech, swallowing, or other functions.

There is no way to predict rate of progression or severity of symptoms. Generally, once symptoms begin, progression continues slowly throughout life. For some childhood-onset forms, symptoms become apparent, gradually worsen during childhood, and then stabilize after adolescence.

Healthcare providers use several methods to diagnose hereditary spastic paraplegia (HSP). They’ll take a family and medical history to learn about the person’s symptoms and whether family members have similar issues. Doctors will also do an exam to check muscle strength, reflexes, coordination, and walking ability. This physical and neurological exam can help identify signs of muscle stiffness (spasticity) that may indicate HSP. 

The healthcare provider may also order genetic testing that looks for changes in specific genes linked to HSP. This testing can confirm an HSP diagnosis and identify the type. Doctors can diagnose HSP if genetic testing identifies a related gene mutation and the symptoms align with the condition. If genetic testing is inconclusive, doctors may base the diagnosis on the person’s medical history, physical exam, and test results.

In some cases, doctors may order imaging tests such as an MRI (magnetic resonance imaging), to check for brain or spinal cord issues that may explain the symptoms. Although HSP usually doesn’t cause structural changes, an MRI can help rule out other conditions.

Blood tests, nerve conduction studies, or lumbar punctures can rule out other conditions with similar symptoms.

Currently, no treatments can prevent, slow, or reverse HSP. However, treatments are available to help manage symptoms. For example, muscle relaxers may help reduce stiffness in the legs. Some people benefit from surgery to loosen tight muscles. Assistive devices like braces, walkers, or wheelchairs can also improve mobility. Regular physical therapy can help people with HSP maintain muscle strength and flexibility.

The outlook for people with HSP varies. Some people experience severe disability, while others have only mild symptoms. Most people with HSP have a normal life expectancy.