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12 | InTouch SUMMER 2023 Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis (FSP), refers to a group of inherited disorders that are quite different in their cause and presentation. What is Hereditary Spastic Paraplegia? Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis (FSP), refers to a group of inherited disorders that are quite different in their cause and presentation, but all share the trait of weakness and spasticity (stiffness). In most cases, the initial symptom of HSP is walking difficulty caused by leg weakness and spasticity, resulting in what is known as a spastic gait. Spastic gait is characterized by stiffness and bounce in the legs with a tendency to hold the knees together while the feet scuff the floor. Urinary urgency is also common and may be an early sign of HSP. This condition has a slow progressive course which may result in the person requiring the assistance of a cane, walker, or wheelchair. The number of people who have HSP varies from population to population with an overall prevalence of approximately 1 to 10 per 100,000 people. Varieties of HSP Pure or uncomplicated HSP presents with the primary features of HSP as described above. Other forms can be more complicated and may include additional neurologic or systemic symptoms such as peripheral neuropathy, dysarthria (abnormal speech), ataxia (lack of muscle Hereditary Spastic Paraplegia/ Familial Spastic Paraparesis YOUR CONDITION IN REVIEW coordination), epilepsy, visual loss, hearing loss, cardiomyopathy, skeletal abnormalities, and/or cognitive impairment. Symptoms may begin in childhood or adulthood, depending on the gene involved, and the rate of progression is highly variable. When symptoms begin after childhood they usually progress slowly and steadily. If symptoms start in early childhood, they may not progress and therefore resemble spastic diplegic cerebral palsy. The severity of the condition varies with some people being severely disabled and others only mildly. Life expectancy for uncomplicated HSP is not affected. Causes of HSP More than 80 genetic types of HSP have been described. These genes generally encode proteins that help maintain the function of the corticospinal tract axons within the spinal cord, which are responsible for conducting nerve impulses related to the voluntary use of muscles. Inheritance HSP has several patterns of inheritance, depending on the specific gene defect that is causing the condition. Not all children in a family will necessarily develop symptoms, although they may be carriers of the affected gene. The following inheritance patterns have been described in HSP: X-linked recessive: X-linked HSP is caused by a defect in a gene on the X chromosome. One functioning copy is enough to prevent symptoms of X-linked HSP. Girls receive an X from mum and an X from dad and are described as XX. Boys receive an X from mum and a Y from dad and are described as XY. As males have only one X chromosome, if they inherit an X chromosome with a defective gene, they will develop X-linked HSP. In contrast, females have two X chromosomes, and if they inherit one X chromosome with the defective gene, they will be carriers, but will not develop symptoms of HSP as they HSP has several patterns of inheritance, depending on the specific gene defect that is causing the condition. Not all children in a family will necessarily develop symptoms, although they may be carriers of the affected gene.