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Spastic paraplegia type 7
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Reviewed January 2008
What is spastic paraplegia type 7?
Spastic paraplegia type 7 is part of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and the development of paralysis of the lower limbs (paraplegia). Hereditary spastic paraplegias are divided into two types: pure and complex. The pure types involve the lower limbs. The complex types involve the lower limbs and can also affect the upper limbs to a lesser degree; the structure or functioning of the brain; and the nerves connecting the brain and spinal cord to muscles and sensory cells that detect sensations such as touch, pain, heat, and sound (the peripheral nervous system). Spastic paraplegia type 7 can occur in either the pure or complex form.
Like all hereditary spastic paraplegias, spastic paraplegia type 7 involves spasticity of the leg muscles and increased muscle weakness. People with this form of spastic paraplegia can also experience exaggerated reflexes (hyperreflexia) in the arms; speech difficulties (dysarthria); difficulty swallowing (dysphagia); involuntary movements of the eyes (nystagmus); mild hearing loss; abnormal curvature of the spine (scoliosis); high-arched feet (pes cavus); numbness, tingling, or pain in the arms and legs (sensory neuropathy); disturbance in the nerves used for muscle movement (motor neuropathy); and muscle wasting (amyotrophy). The onset of symptoms varies greatly among those with spastic paraplegia type 7; however, abnormalities in muscle tone and other features are usually noticeable in adulthood.
How common is spastic paraplegia type 7?
The prevalence of all hereditary spastic paraplegias combined is estimated to be 2 to 6 in 100,000 people worldwide. Spastic paraplegia type 7 likely accounts for only a small percentage of all spastic paraplegia cases.
What genes are related to spastic paraplegia type 7?
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 is responsible for assembling ribosomes (cellular structures that process the cell's genetic instructions to create proteins) and removing nonfunctional proteins in the mitochondria. When there is a mutation in paraplegin, the m-AAA protease cannot function correctly. Nonfunctional m-AAA proteases cause a build up of unusable proteins in the mitochondria of nerve cells, which can result in swelling of the cell, reduced cell signaling, and impaired cell movement, leading to the major signs and symptoms of spastic paraplegia type 7.
Read more about the SPG7 gene.
How do people inherit spastic paraplegia type 7?
This condition 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.
Where can I find information about diagnosis or management of spastic paraplegia type 7?
These resources address the diagnosis or management of spastic paraplegia type 7 and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about spastic paraplegia type 7?
You may find the following resources about spastic paraplegia type 7 helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for spastic paraplegia type 7?
What if I still have specific questions about spastic paraplegia type 7?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding spastic paraplegia type 7?
autosomal ; autosomal recessive ; cell ; deficiency ; difficulty swallowing ; dysarthria ; dysphagia ; gene ; involuntary ; mitochondria ; motor ; muscle tone ; mutation ; nervous system ; neuropathy ; nystagmus ; oxidative phosphorylation ; paraplegia ; peripheral ; peripheral nervous system ; pes cavus ; phosphorylation ; prevalence ; protease ; protein ; recessive ; ribosomes ; scoliosis ; sensory cells ; sensory neuropathy ; spasticity ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (7 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.