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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Spastic paraplegia type 3A

Reviewed March 2015

What is spastic paraplegia type 3A?

Spastic paraplegia type 3A is one of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by muscle stiffness (spasticity) and weakness in the lower limbs (paraplegia). Hereditary spastic paraplegias are often divided into two types: pure and complex. The pure types involve only the lower limbs, while the complex types also involve other areas of the body; additional features can include changes in vision, changes in intellectual functioning, difficulty walking, and disturbances in nerve function (neuropathy). Spastic paraplegia type 3A is usually a pure hereditary spastic paraplegia, although a few complex cases have been reported.

In addition to spasticity and weakness, which typically affect both legs equally, people with spastic paraplegia type 3A can also experience progressive muscle wasting (amyotrophy) in the lower limbs, reduced bladder control, an abnormal curvature of the spine (scoliosis), loss of sensation in the feet (peripheral neuropathy), or high arches of the feet (pes cavus). The signs and symptoms of spastic paraplegia type 3A usually appear before the age of 10; the average age of onset is 4 years. In some affected individuals the condition slowly worsens over time, sometimes leading to a need for walking support.

How common is spastic paraplegia type 3A?

Spastic paraplegia type 3A belongs to a subgroup of hereditary spastic paraplegias known as autosomal dominant hereditary spastic paraplegia, which has an estimated prevalence of 2 to 9 per 100,000 individuals. Spastic paraplegia type 3A accounts for 10 to 15 percent of all autosomal dominant hereditary spastic paraplegia cases.

What genes are related to spastic paraplegia type 3A?

Mutations in the ATL1 gene cause spastic paraplegia type 3A. The ATL1 gene provides instructions for producing a protein called atlastin-1. Atlastin-1 is produced primarily in the brain and spinal cord (central nervous system), particularly in nerve cells (neurons) that extend down the spinal cord (corticospinal tracts). These neurons send electrical signals that lead to voluntary muscle movement. Atlastin-1 is involved in the growth of specialized extensions of neurons, called axons, which transmit nerve impulses that signal muscle movement. The protein also likely plays a role in the normal functioning of multiple structures within neurons and in distributing materials within these cells.

ATL1 gene mutations likely lead to a shortage of normal atlastin-1 protein, which impairs the functioning of neurons, including the distribution of materials within these cells. This lack of functional atlastin-1 protein may also restrict the growth of axons. These problems can lead to the abnormal functioning or death of the long neurons of the corticospinal tracts. As a result, the neurons are unable to transmit nerve impulses, particularly to other neurons and muscles in the lower extremities. This impaired nerve function leads to the signs and symptoms of spastic paraplegia type 3A.

Related Gene(s)

Changes in this gene are associated with spastic paraplegia type 3A.

  • ATL1

How do people inherit spastic paraplegia type 3A?

Spastic paraplegia type 3A is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In approximately 95 percent of cases, an affected person inherits the mutation from one affected parent.

Where can I find information about diagnosis or management of spastic paraplegia type 3A?

These resources address the diagnosis or management of spastic paraplegia type 3A and may include treatment providers.

  • Gene Review: Hereditary Spastic Paraplegia Overview (
  • Gene Review: Spastic Paraplegia 3A (
  • Genetic Testing Registry: Spastic paraplegia 3 (
  • Spastic Paraplegia Foundation, Inc.: Treatments and Therapies (

You might also find information on the diagnosis or management of spastic paraplegia type 3A in Educational resources and Patient support.

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 3A?

You may find the following resources about spastic paraplegia type 3A 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 3A?

  • spastic paraplegia 3
  • spastic paraplegia 3A
  • SPG3A

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about spastic paraplegia type 3A?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding spastic paraplegia type 3A?

autosomal ; autosomal dominant ; axons ; cell ; central nervous system ; gene ; hereditary ; inherited ; mutation ; nervous system ; neuropathy ; paraplegia ; peripheral ; peripheral neuropathy ; pes cavus ; prevalence ; protein ; scoliosis ; spasticity ; voluntary muscle ; wasting

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


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  • Blackstone C. Cellular pathways of hereditary spastic paraplegia. Annu Rev Neurosci. 2012;35:25-47. doi: 10.1146/annurev-neuro-062111-150400. Epub 2012 Apr 20. Review. (
  • Ivanova N, Claeys KG, Deconinck T, Litvinenko I, Jordanova A, Auer-Grumbach M, Haberlova J, Löfgren A, Smeyers G, Nelis E, Mercelis R, Plecko B, Priller J, Zámecník J, Ceulemans B, Erichsen AK, Björck E, Nicholson G, Sereda MW, Seeman P, Kremensky I, Mitev V, De Jonghe P. Hereditary spastic paraplegia 3A associated with axonal neuropathy. Arch Neurol. 2007 May;64(5):706-13. (
  • Leonardi L, Marcotulli C, Santorelli FM, Tessa A, Casali C. De novo mutations in SPG3A: a challenge in differential diagnosis and genetic counselling. Neurol Sci. 2015 Jun;36(6):1063-4. doi: 10.1007/s10072-015-2097-1. Epub 2015 Jan 31. (
  • Leonardis L, Auer-Grumbach M, Papić L, Zidar J. The N355K atlastin 1 mutation is associated with hereditary sensory neuropathy and pyramidal tract features. Eur J Neurol. 2012 Jul;19(7):992-8. doi: 10.1111/j.1468-1331.2012.03665.x. Epub 2012 Feb 16. (
  • Namekawa M, Ribai P, Nelson I, Forlani S, Fellmann F, Goizet C, Depienne C, Stevanin G, Ruberg M, Dürr A, Brice A. SPG3A is the most frequent cause of hereditary spastic paraplegia with onset before age 10 years. Neurology. 2006 Jan 10;66(1):112-4. (
  • Zhu PP, Soderblom C, Tao-Cheng JH, Stadler J, Blackstone C. SPG3A protein atlastin-1 is enriched in growth cones and promotes axon elongation during neuronal development. Hum Mol Genet. 2006 Apr 15;15(8):1343-53. Epub 2006 Mar 14. (


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.

Reviewed: March 2015
Published: November 23, 2015