Spastic paraplegia type 7 (also called SPG7) is one of more than 80 genetic disorders known as hereditary spastic paraplegias. These disorders primarily affect the brain and spinal cord (central nervous system), specifically nerve cells (neurons) that extend down the spinal cord. These neurons are used for muscle movement and sensation. Signs and symptoms of hereditary spastic paraplegias are characterized by progressive muscle stiffness (spasticity) in the legs and difficulty walking.
Mutations in the SPG7 gene cause spastic paraplegia type 7. The SPG7 gene provides instructions for producing a protein called paraplegin. Located within the inner membrane of the energy-producing centers of cells (mitochondria), paraplegin is one of the proteins that form a complex called the m-AAA protease. The m-AAA protease acts as an enzyme and is responsible for assembling ribosomes (cellular structures that process the cell's genetic instructions to create proteins) and removing nonfunctional proteins in the mitochondria.
The prevalence of all hereditary spastic paraplegias combined is estimated to be 2 to 6 in 100,000 people worldwide. This group of conditions is the most common cause of inherited spasticity. Spastic paraplegia type 7 likely accounts for only a small percentage of all spastic paraplegia cases.
In most cases, spastic paraplegia type 7 is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Published Date: June 25, 2021Published By: National Institutes of Health