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

Troyer syndrome

Reviewed January 2008

What is Troyer syndrome?

Troyer syndrome 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). Troyer syndrome is a complex hereditary spastic paraplegia.

People with Troyer syndrome can experience a variety of signs and symptoms. The most common characteristics of Troyer syndrome are spasticity of the leg muscles, progressive muscle weakness, paraplegia, muscle wasting in the hands and feet (distal amyotrophy), small stature, developmental delay, learning disorders, speech difficulties (dysarthria), and mood swings. Other characteristics can include exaggerated reflexes (hyperreflexia) in the lower limbs, uncontrollable movements of the limbs (choreoathetosis), skeletal abnormalities, and a bending outward (valgus) of the knees.

Troyer syndrome causes the degeneration and death of muscle cells and motor neurons (specialized nerve cells that control muscle movement) throughout a person's lifetime, leading to a slow progressive decline in muscle and nerve function. The severity of impairment related to Troyer syndrome increases as a person ages. Most affected individuals require a wheelchair by the time they are in their fifties or sixties.

How common is Troyer syndrome?

About 20 cases of Troyer syndrome have been reported in the Old Order Amish population of Ohio. It has not been found outside this population.

What genes are related to Troyer syndrome?

Troyer syndrome is caused by a mutation in the SPG20 gene. The SPG20 gene provides instructions for producing a protein called spartin, whose function is not entirely understood. Researchers believe that spartin may be involved in a variety of cell functions, from breaking down proteins to transporting materials from the cell surface into the cell (endocytosis). Spartin is found in a wide range of body tissues, including the nervous system.

Related Gene(s)

Changes in this gene are associated with Troyer syndrome.

  • SPG20

How do people inherit Troyer syndrome?

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 Troyer syndrome?

These resources address the diagnosis or management of Troyer syndrome and may include treatment providers.

  • Gene Review: Hereditary Spastic Paraplegia Overview (
  • Gene Review: Troyer Syndrome (
  • Genetic Testing Registry: Troyer syndrome (
  • Spastic Paraplegia Foundation, Inc.: Treatments and Therapies (

You might also find information on the diagnosis or management of Troyer syndrome 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 Troyer syndrome?

You may find the following resources about Troyer syndrome 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 Troyer syndrome?

  • Autosomal Recessive Hereditary Spastic Paraplegia
  • Cross-McKusick syndrome
  • Hereditary Spastic Paraplegia
  • spastic paraparesis, childhood-onset, with distal muscle wasting
  • spastic paraplegia 20, autosomal recessive
  • spastic paraplegia, autosomal recessive, Troyer type
  • SPG20

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 Troyer syndrome?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding Troyer syndrome?

autosomal ; autosomal recessive ; cell ; developmental delay ; distal ; dysarthria ; endocytosis ; gene ; hereditary ; inherited ; motor ; muscle cells ; mutation ; nervous system ; paraparesis ; paraplegia ; peripheral ; peripheral nervous system ; population ; protein ; recessive ; sensory cells ; spasticity ; stature ; syndrome ; wasting

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


  • Auer-Grumbach M, Fazekas F, Radner H, Irmler A, Strasser-Fuchs S, Hartung HP. Troyer syndrome: a combination of central brain abnormality and motor neuron disease? J Neurol. 1999 Jul;246(7):556-61. (
  • Bakowska JC, Jupille H, Fatheddin P, Puertollano R, Blackstone C. Troyer syndrome protein spartin is mono-ubiquitinated and functions in EGF receptor trafficking. Mol Biol Cell. 2007 May;18(5):1683-92. Epub 2007 Mar 1. (
  • Burgunder JM, Hunziker W. Hereditary spastic paraplegia: clues from a rare disorder for a common problem? IUBMB Life. 2003 Jun;55(6):347-52. Review. (
  • Patel H, Cross H, Proukakis C, Hershberger R, Bork P, Ciccarelli FD, Patton MA, McKusick VA, Crosby AH. SPG20 is mutated in Troyer syndrome, an hereditary spastic paraplegia. Nat Genet. 2002 Aug;31(4):347-8. Epub 2002 Jul 22. (
  • Proukakis C, Cross H, Patel H, Patton MA, Valentine A, Crosby AH. Troyer syndrome revisited. A clinical and radiological study of a complicated hereditary spastic paraplegia. J Neurol. 2004 Sep;251(9):1105-10. (
  • Reid E. Science in motion: common molecular pathological themes emerge in the hereditary spastic paraplegias. J Med Genet. 2003 Feb;40(2):81-6. Review. (


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: January 2008
Published: February 1, 2016