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Genetic and Rare Diseases Information Center (GARD)

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Hereditary spastic paraplegia


Other Names for this Disease

  • Familial spastic paraparesis
  • FSP
  • HSP
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

Can hereditary spastic paraplegia be inherited from grandparent to grandchild (skipping the parent), or is it directly inherited from parent to child only?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is hereditary spastic paraplegia?

Hereditary spastic paraplegia is a group of hereditary, degenerative, neurological disorders that primarily affect the upper motor neurons. Upper motor neurons in the brain and spinal cord deliver signals to the lower motor neurons which in turn, carry messages to the muscles. In hereditary spastic paraplegia, upper motor neurons slowly degenerate so the muscles do not receive the correct messages causing progressive spasticity (increased muscle tone/stiffness) and weakness of the legs leading to difficulty walking.  As degeneration continues, symptoms worsen.[1] 
Last updated: 1/31/2013

How is hereditary spastic paraplegia (HSP) inherited?

At this point, over 30 different types of HSP have been described. The different patterns of inheritance are autosomal dominant, autosomal recessive, and X-linked recessive.[2]
Last updated: 10/7/2011

What is autosomal dominant inheritance?

Autosomal dominant inheritance is when one mutated copy of the gene that causes a disorder in each cell is needed for a person to be affected. Autosomal dominant conditions may occur for the first time in a person in a family due to a spontaneous gene mutation, or these conditions may be inherited from an affected parent. When a person with an autosomal dominant disorder has a child, there is a 50% chance that their child will inherit the condition.[3]
Last updated: 12/3/2009

What is autosomal recessive inheritance?

Autosomal recessive inheritance refers to the inheritance pattern in which two mutated copies of the gene that causes a disorder are present in each cell. An affected person usually has unaffected parents who each carry a single copy of the mutated gene (and are referred to as carriers). Autosomal recessive disorders are typically not seen in every generation of an affected family. When two people who are carriers of an autosomal recessive condition have a child, there is a 25% (1 in 4) chance that the child will be affected.[3]

Last updated: 2/18/2009

What is X-linked recessive inheritance?

X-linked recessive disorders are caused by mutations in genes on the X chromosome. Males are more frequently affected than females, and the chance of passing on the disorder differs between men and women. Families with an X-linked recessive disorder often have affected males in each generation, and rarely have affected females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.[3]
 
In this example, a man with an X-linked recessive condition has two unaffected daughters who each carry one copy of the gene mutation, and two unaffected sons who do not have the mutation. In this example, an unaffected woman carries one copy of a gene mutation for an X-linked recessive disorder.  She has an affected son, an unaffected daughter who carries one copy of the mutation, and two unaffected children who do not have the mutation.

     
 
  
Last updated: 6/28/2013

Can hereditary spastic paraplegia (HSP) skip a generation?

In some types of HSP, an affected person can have an unaffected child and an affected grandchild. The most likely way for it to appear as if HSP has skipped a generation, is if the type of HSP has autosomal dominant or X-linked recessive inheritance.

In some conditions with autosomal dominant inheritance, a person can inherit the genetic change that causes the disorder but not develop the condition. This phenomenon is called incomplete or reduced penetrance. If this person's children also inherits the genetic change, they may or may not be affected with the disorder. When a disorder has reduced penetrance, it may appear as if the disorder has skipped a generation if the disorder is only penetrant in the grandparent and the grandchild. Reduced penetrance has been reported for some types of autosomal dominant HSP.[4]

X-linked HSP can appear to skip a generation because an affected male can only pass his X chromosome to his daughters and not his sons. All of his sons will be unaffected and his daughters will be unaffected carriers. For example, if a man with X-linked HSP has a daughter, she will be an unaffected carrier of HSP. This woman's sons each have a 50% chance of inheriting the condition.[4]
Last updated: 6/28/2013

References
Other Names for this Disease
  • Familial spastic paraparesis
  • FSP
  • HSP
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.