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Troyer Syndrome

, PhD, , MRes, and , PhD.

Author Information
, PhD
Medical Genetics
St George’s, University of London
London, United Kingdom
, MRes
Medical Genetics
St George’s, University of London
London, United Kingdom
, PhD
Medical Genetics
St George’s, University of London
London, United Kingdom

Initial Posting: ; Last Update: August 4, 2011.

Summary

Disease characteristics. Troyer syndrome is characterized by progressive spastic paraparesis, dysarthria, and pseudobulbar palsy; distal amyotrophy; motor and cognitive delays; short stature; and subtle skeletal abnormalities. Most affected children exhibit delays in walking and talking followed by slow deterioration in both gait and speech. Emotional lability and affective disorders, such as inappropriate euphoria and/or crying, are common. Mild cerebellar signs are common. The most severely affected individuals have choreoathetosis. Life expectancy is normal.

Diagnosis/testing. The diagnosis of Troyer syndrome relies on clinical findings and molecular genetic testing of SPG20, which encodes the protein spartin. The two pathogenic SPG20 mutations were identified in an extended Old Order Amish family and a third was observed in two related Omani families.

Management. Treatment of manifestations: Antispasticity drugs; antidepressant medication for individuals with emotional lability.

Prevention of secondary complications: Good nursing care and physiotherapy during disease progression and monitoring for dysphagia to reduce risk of aspiration.

Surveillance: Follow-up neurologic examination; cognitive testing; repeat skeletal survey.

Genetic counseling. Troyer syndrome is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if both disease-causing mutations have been identified in an affected family member.

Diagnosis

Clinical Diagnosis

The clinical features of Troyer syndrome include the following:

  • Age at first symptoms: one to two years
  • Early onset: delayed walking, delayed speech, dysarthria
  • Pyramidal signs: spasticity (i.e., hypertonia in which resistance to externally imposed movement increases with increasing speed of stretch and varies with the direction of joint movement); hyperreflexia; extensor plantar responses
  • Extrapyramidal signs: mild choreoathetoid movements
  • Cortical signs: emotional lability
  • Cerebellar signs: dysdiadochokinesia, mild intention tremor
  • Amyotrophy: small muscles of hands and feet with symmetric involvement
  • Skeletal abnormalities: pes cavus, mild talipes equinovarus, short stature, kyphoscoliosis
  • Progression of disease: variable
  • Brain MRI (performed in 3 affected individuals): white matter abnormalities, particularly in the temporoparietal periventricular area
  • Life expectancy: normal

Molecular Genetic Testing

Gene. SPG20, which encodes the protein spartin, is the only gene in which mutations are known to cause Troyer syndrome.

Table 1. Summary of Molecular Genetic Testing Used in Troyer Syndrome

Gene SymbolTest MethodMutations DetectedMutation Detection Frequency by Test Method 1
Amish OmaniOther Populations
SPG20Sequence analysisSequence variants 2, 3100% for c.1110delA 4100% for c.364_365delAT 5Unknown
Targeted mutation analysisc.1110delA; c.364_365delATUnknown

1. The ability of the test method used to detect a mutation that is present in the indicated gene

2. Examples of mutations detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site mutations.

3. Includes the c.1110delA and c.364_365delAT mutation that may also be identified by targeted mutation analysis

4. The causative mutation in an extended Old Order Amish pedigree [Patel et al 2002]

5. The causative mutation in two related Omani families [Manzini et al 2010]

Interpretation of test results. For issues to consider in interpretation of sequence analysis results, click here.

Testing Strategy

To confirm/establish the diagnosis in a proband. In individuals with clinical findings consistent with Troyer syndrome and a family history consistent with autosomal recessive inheritance:

1.

Targeted mutation analysis for the SPG20 mutations:

a.

c.1110delA in individuals of Old Order Amish heritage

b.

c.364_365delAT in individuals of Omani heritage

2.

If the mutations are not detected, sequence analysis of all SPG20 exons including intron-exon splice sites.

Carrier testing for at-risk relatives requires prior identification of the disease-causing mutations in the family.

Note: Carriers are heterozygotes for this autosomal recessive disorder and are not at risk of developing the disorder.

Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutations in the family.

Clinical Description

Natural History

Troyer syndrome is characterized by both developmental and degenerative processes: findings apparent from infancy progress slowly. The cardinal features of Troyer syndrome include spastic paraparesis, dysarthria, distal amyotrophy, and short stature [Proukakis et al 2004].

Twenty-one individuals with Troyer syndrome in an Old Order Amish population in Ohio, USA including three from the original study by Cross & McKusick [1967] [Patel et al 2002] and six individuals in two related Omani families [Manzini et al 2010] have been reported.

In the Old Order Amish, the presenting feature in most individuals was a delay in reaching early milestones (walking and talking) compared to unaffected sibs. Twenty of the 21 individuals were delayed in walking (age range 12 to 22 months; mean age 16.1 months). The age at which they started talking ranged from seven to 36 months, with a mean age of 17.5 months. In those whose milestones were not noticeably delayed, the character of the gait and/or speech was the first abnormality reported.

Slow deterioration in both gait and speech was observed: spastic paraparesis with lower limb hyperreflexia and spastic dysarthria were present in all, severity being greater in older individuals compared to younger ones. Jaw jerk was brisk in the majority, often accompanied by slow, spastic tongue movements. Excessive drooling was observed in the most advanced cases.

Distal amyotrophy was found in all individuals over age 13 years and also in one seven-year-old child. In the more severely affected, generally older, individuals, weakness of the small hand muscles was observed. Most individuals had mild weakness of the abductor pollicis brevis, abductor digiti minimi, and palmar and dorsal interossei.

More proximal upper limb strength was preserved in all cases; lower limb weakness when present was mild and disproportionate to the observed spasticity.

The most severely affected individuals had choreoathetoid movements (i.e., an irregular, constant succession of slow, spasmodic writhing with involuntary flexion, extension, pronation, and supination) of the fingers and hands, and sometimes the toes and feet.

Difficulty with walking increased with age; affected individuals generally became wheelchair-bound during the sixth to seventh decade of life.

Learning difficulties were reported in all but one person. Most were able to complete eighth grade, the traditional limit of Amish education. In all but one case, school performance was significantly worse than that of unaffected sibs. Two individuals completed high school and work for several years.

Emotional lability and affective disorders including inappropriate euphoria and/or crying were common.

Mild skeletal abnormalities included the following:

  • Short stature in all individuals when compared to parents and/or sibs
  • Small feet with pes cavus (17/21 individuals)
  • “Hammer toes" in the most severely affected individuals
  • Hyperextensible proximal interphalangeal joints of the fingers (8/21)
  • Mild knee valgus (4/21)
  • Mild kyphoscoliosis: present in some; radiographic correlation not available

In the two related Omani families, all affected individuals had dysarthria and delays in motor and cognitive development. All had difficulties walking with a clumsy, mildly spastic gait, reported to worsen over time. The most common physical features were short stature; relative hypertelorism; overgrowth of the maxilla leading to overbite; and hand and foot anomalies including brachydactyly (5/6 individuals), hammer toes, and pes cavus. Additional nonspecific hand findings were clinodactyly, camptodactyly, and hypoplastic fifth middle phalanges. Most affected individuals had persistent cognitive deficits and poor performance in school; emotional lability was not reported.

The mean age of individuals in the Omani families (16.6 years) was younger than in the Old Order Amish individuals. To evaluate the natural history, the Amish cohort was divided into a younger set (Amish I) comparable in age to the Omani cohort (<27 years; mean age 15 years) and an older set (Amish II; >28 years; mean age, 43.5 years). The findings in the Omani cohort closely matched those of Amish I group. The Amish II group was more severely affected, consistent with the progressive nature of Troyer syndrome.

Additional studies in the Old Order Amish families:

  • Nerve conduction studies performed in two individuals who were not severely affected were normal in the right upper and lower limb. In one of these individuals, electromyography (EMG) was normal bilaterally except for a polyphasic potential in the medial head of the gastrocnemius on one side. In the other individual, EMG of the right upper and lower limb was normal.
  • White matter abnormalities have been noted on brain MRI imaging [Proukakis et al 2004].

Genotype-Phenotype Correlations

No phenotype genotype phenotype correlations have been observed.

Prevalence

The prevalence is unknown. A previous study documented 21 individuals with Troyer syndrome in a population of approximately 50,000 Amish [Patel et al 2002]. Six of seventeen individuals in two related Omani families were found to be affected [Manzini et al 2010].

Carrier frequency is about 7.5% in the Old Order Amish community [Cross & McKusick 1967].

Several similar cases have been reported around the world; however, some clinical features differ from those in the original description of Troyer syndrome [Neuhauser et al 1976, Farag et al 1994, Malandrini et al 1996, Farah et al 1997, Bertini et al 1998, Auer-Grumbach et al 1999]. To date the c.1110delA mutation has not been observed outside of the Old Order Amish population and the c.364_365delAT mutation has not been observed outside the Omani population [Manzini et al 2010].

Differential Diagnosis

See Hereditary Spastic Paraplegia Overview for a review.

Troyer syndrome shares some features with ARSACS (autosomal recessive spastic ataxia of Charlevoix-Saguenay); however, nystagmus, abnormalities of ocular movement, and mitral valve prolapse are not features of Troyer syndrome.

Note to clinicians: For a patient-specific ‘simultaneous consult’ related to this disorder, go to Image SimulConsult.jpg, an interactive diagnostic decision support software tool that provides differential diagnoses based on patient findings (registration or institutional access required).

Management

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs of an individual diagnosed with Troyer syndrome, the following evaluations are recommended:

  • Height
  • Occipitofrontal circumference (OFC)
  • Speech and language development with attention to possible dysarthria and tongue dyspraxia
  • Gross motor and fine motor skills
  • Neurologic examination with attention to evidence of pyramidal and/or extrapyramidal movement disorders, distal amyotrophy, hyperreflexia
  • School performance
  • Emotional status, including presence or absence of emotional lability
  • Skeletal abnormalities and skeletal x-rays as needed
  • Brain MRI
  • EMG

Treatment of Manifestations

Treatment for spasticity is presently limited to reducing muscle spasticity through exercise and medication, especially Lioresal®, which is given either orally or via intrathecal pump. Dosages need to be individualized as some patients have mainly weakness with less spasticity (and thus do not benefit from large doses), while others have significant spasticity and require high doses. Tizanidine, dantrolene (see, however, Agents/Circumstances to Avoid), and Botox® have also been useful in reducing muscle spasticity.

It is recommended that affected individuals participate in daily physical therapy designed to:

  • Maintain and improve muscle flexibility and range of motion (stretching exercises);
  • Improve muscle strength (through resistance exercise);
  • Maintain walking reflexes (walking on a slowly moving treadmill with arm supports or walking in a swimming pool); and
  • Improve cardiovascular fitness.

These recommendations are based on the experience of approximately 200 persons with hereditary spastic paraplegia, who nearly unanimously reported benefit from daily physical exercise [Fink 2003].

Occupational therapy, assistive walking devices, and ankle-foot orthotics as needed are appropriate.

Oxybutynin is helpful in reducing urinary urgency.

Antidepressants or mood stabilizers can be prescribed to manage emotional lability.

See also Hereditary Spastic Paraplegia Overview.

Prevention of Secondary Complications

Provide good nursing care and physiotherapy during disease progression; monitor for dysphagia to reduce risk of aspiration.

Surveillance

The following are appropriate:

  • Specialized outpatient evaluations every six months to update medications and physical rehabilitation
  • Cognitive testing
  • Repeat skeletal survey

Agents/Circumstances to Avoid

Dantrolene should be avoided in persons who are ambulatory as it may induce irreversible weakness, which can adversely interfere with overall mobility.

Therapies Under Investigation

Search ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions.

Genetic Counseling

Genetic counseling is the process of providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions. The following section deals with genetic risk assessment and the use of family history and genetic testing to clarify genetic status for family members. This section is not meant to address all personal, cultural, or ethical issues that individuals may face or to substitute for consultation with a genetics professional. —ED.

Mode of Inheritance

Troyer syndrome is inherited in an autosomal recessive manner.

Risk to Family Members

Parents of a proband

  • The parents of an affected individual are obligate heterozygotes and therefore carry one mutant allele.
  • Heterozygotes (carriers) are unaffected.

Sibs of a proband

  • At conception, the sibs of an affected individual have a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
  • Once an at-risk sib is known to be unaffected, the risk of his/her being a carrier is 2/3.
  • Heterozygotes (carriers) are unaffected.

Offspring of a proband. While the effect of homozygous SPG20 mutations on fertility is not known, no individual with Troyer syndrome is known to have had children [Patel & Crosby, personal observation].

Other family members of a proband. Sibs of the proband's parents are at 50% risk of being carriers.

Carrier Detection

Carrier testing for at-risk family members is possible if the disease-causing mutations have been identified in an affected family member.

Related Genetic Counseling Issues

Family planning

  • The optimal time for determination of genetic risk, clarification of carrier status, and discussion of the availability of prenatal testing is before pregnancy.
  • It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected, are carriers, or are at risk of being carriers.

DNA banking is the storage of DNA (typically extracted from white blood cells) for possible future use. Because it is likely that testing methodology and our understanding of genes, mutations, and diseases will improve in the future, consideration should be given to banking DNA of affected individuals.

Prenatal Testing

If the disease-causing mutations have been identified in the family, prenatal diagnosis for pregnancies at increased risk is possible by analysis of DNA extracted from fetal cells obtained by amniocentesis (usually performed at ~15-18 weeks’ gestation) or chorionic villus sampling (usually performed at ~10-12 weeks’ gestation).

Note: Gestational age is expressed as menstrual weeks calculated either from the first day of the last normal menstrual period or by ultrasound measurements.

Preimplantation genetic diagnosis (PGD) may be an option for some families in which the disease-causing mutations have been identified.

Resources

GeneReviews staff has selected the following disease-specific and/or umbrella support organizations and/or registries for the benefit of individuals with this disorder and their families. GeneReviews is not responsible for the information provided by other organizations. For information on selection criteria, click here.

  • Spastic Paraplegia Foundation, Inc.
    PO Box 1208
    Fortson GA 31808-1208
    Phone: 877-773-4483 (toll-free)
    Email: information@sp-foundation.org
  • National Ataxia Foundation
    2600 Fernbrook Lane
    Suite 119
    Minneapolis MN 55447
    Phone: 763-553-0020
    Email: naf@ataxia.org

Molecular Genetics

Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.

Table A. Troyer Syndrome: Genes and Databases

Locus NameGene SymbolChromosomal LocusProtein NameLocus SpecificHGMD
SPG20SPG2013q13​.3SpartinSPG20 homepage - Mendelian genes
HSP mutation database (SPG20)
SPG20

Data are compiled from the following standard references: gene symbol from HGNC; chromosomal locus, locus name, critical region, complementation group from OMIM; protein name from UniProt. For a description of databases (Locus Specific, HGMD) to which links are provided, click here.

Table B. OMIM Entries for Troyer Syndrome (View All in OMIM)

275900SPASTIC PARAPLEGIA 20, AUTOSOMAL RECESSIVE; SPG20
607111SPG20 GENE; SPG20

Molecular Genetic Pathogenesis

The pathogenic basis of Troyer syndrome is currently unclear.

Normal allelic variants. SPG20 resides within 731 kb and comprises nine exons. Multiple alternatively spliced variants, encoding the same protein, have been identified. Two normal benign variants have been identified (Table 2): c.1629A>G in a family of European descent and c.1130A>T in a non-Amish control of European descent.

Pathologic allelic variants. Only two pathogenic SPG20 mutations have been identified to date: c.1110delA in exon 4 in an extended Old Order Amish pedigree [Patel et al 2002] and c.364_365delAT in exon 1 in two related Omani families [Manzini et al 2010].

Table 2. Selected SPG20 Allelic Variants

Class of Variant AlleleDNA Nucleotide ChangeProtein Amino Acid Change
(Alias 1)
Reference Sequences
Normal c.1629A>Gp.AlaA543AlaNM_015087​.4
NP_055902​.1
c.1130A>Tp.Lys377Met
Pathologicc.1110delAp.Lys370Asnfs*30
(fs369-398X399)
c.364_365delATp.Met122Valfs*2 (M122V_C123X)

Note on variant classification: Variants listed in the table have been provided by the author(s). GeneReviews staff have not independently verified the classification of variants.

Note on nomenclature: GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org). See Quick Reference for an explanation of nomenclature.

1. Variant designation that does not conform to current naming conventions

Normal gene product. SPG20 is widely expressed in adult and fetal human tissues. It encodes a 666-amino acid protein named spartin (spastic paraplegia autosomal recessive Troyer syndrome). Spartin possesses a MIT domain (contained within microtubule-interacting and trafficking molecules) [Ciccarelli et al 2003] as does spastin, which is encoded by SPAST, the most commonly mutated gene in hereditary spastic paraplegia, accounting for approximately 40% of autosomal dominant cases [Hazan et al 1999] (see Spastic Paraplegia Type 4). The identification of the same domain in spastin and spartin suggests related functionality of these proteins.

Spartin, a cytosolic and membrane-associated protein that interacts with EPS15, an endocytic and trafficking protein, may have a number of roles, including functioning at endosomes and in droplet formation [Bakowska et al 2005]. SPG20 associates with the surface of lipid droplets (LDs), regulating their size and number. SPG20 binds to another LD protein, TIP47; both proteins compete with an additional LD protein, adipophilin/adipocyte differentiation-related protein. Spartin may also be involved in endocytosis and vesicle trafficking [Bakowska et al 2005].

Abnormal gene product. Troyer syndrome is most likely caused by loss of function of spartin, as would be expected with an autosomal recessive disorder. A full explanation for the disease will require an understanding of the normal functions of spartin and the relevance of each function to axonal biology [Edwards et al 2009].

References

Literature Cited

  1. 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;246:556–61. [PubMed: 10463356]
  2. Bakowska JC, Jenkins R, Pendleton J, Blackstone C. The Troyer syndrome (SPG20) protein spartin interacts with Eps15. Biochem Biophys Res Commun. 2005;334:1042–8. [PubMed: 16036216]
  3. Bertini E, Sabatelli M, Di Capua M, Cilio MR, Mignogna T, Federico A, Tonali P. Familial spastic paraplegia, axonal sensory-motor polyneuropathy and bulbar amyotrophy with facial dysmorphia: new cases of Troyer-like syndrome. Eur J Paediatr Neurol. 1998;2:245–54. [PubMed: 10726827]
  4. Ciccarelli FD, Proukakis C, Patel H, Cross H, Azam S, Patton MA, Bork P, Crosby AH. The identification of a conserved domain in both spartin and spastin, mutated in hereditary spastic paraplegia. Genomics. 2003;81:437–41. [PubMed: 12676568]
  5. Cross HE, McKusick VA. The Troyer syndrome. A recessive form of spastic paraplegia with distal muscle wasting. Arch Neurol. 1967;16:473–85. [PubMed: 6022528]
  6. Edwards TL, Clowes VE, Tsang HTH, Connell JW, Sanderson CM, Luzio JP, Reid E. Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5. Biochem J. 2009;423:31–9. [PMC free article: PMC2762690] [PubMed: 19580544]
  7. Farag TI, el-Badramany MH, al-Sharkawy S. Troyer syndrome: report of the first "non-Amish" sibship and review. Am J Med Genet. 1994;53:383–5. [PubMed: 7864052]
  8. Farah S, Sabry MA, al-Shubaili AF, Anim JT, Hussain JM, Montaser MA, Sharfuddin KM. Hereditary spastic paraparesis with distal muscle wasting, microcephaly, mental retardation, arachnodactyly and tremors: new entity? Clin Neurol Neurosurg. 1997;99:66–70. [PubMed: 9107473]
  9. Fink JK. Advances in hereditary spastic paraplegias. Exp Neurol. 2003;184:S106–10. [PubMed: 14597333]
  10. Hazan J, Fonknechten N, Mavel D, Paternotte C, Samson D, Artiguenave F, Davoine CS, Cruaud C, Durr A, Wincker P, Brottier P, Cattolico L, Barbe V, Burgunder JM, Prud'homme JF, Brice A, Fontaine B, Heilig B, Weissenbach J. Spastin, a new AAA protein, is altered in the most frequent form of autosomal dominant spastic paraplegia. Nat Genet. 1999;23:296–303. [PubMed: 10610178]
  11. Malandrini A, Scarpini C, Villanova M, Sicurelli F, Parrotta E, DeFalco D, Guazzi GC. Autosomal recessive paraparesis with amyotrophy of hands and feet and white matter lesions. Acta Neurol Scand. 1996;94:60–2. [PubMed: 8874595]
  12. Manzini MC, Rajab A, Maynard TM, Mochida GH, Tan W, Nasir R, Hill RS, Gleason D, Al Saffar M, Partlow JN, Barry BJ, Vernon M, LaMantia A, Walsh CA. Developmental and degenerative features in a complicated spastic paraplegia. Ann Neurol. 2010;67:516–25. [PMC free article: PMC3027847] [PubMed: 20437587]
  13. Neuhauser G, Wiffler C, Opitz JM. Familial spastic paraplegia with distal muscle wasting in the Old Order Amish; atypical Troyer syndrome or "new" syndrome. Clin Genet. 1976;9:315–23. [PubMed: 1261070]
  14. 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;31:347–8. [PubMed: 12134148]
  15. 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;251:1105–10. [PubMed: 15372254]

Suggested Reading

  1. Eastman SW, Yassaee M, Bieniasz PD. A role for ubiquitin ligases and Spartin/SPG20 in lipid droplet turn over. J Cell Biol. 2009;184:881–94. [PMC free article: PMC2699154] [PubMed: 19307600]

Chapter Notes

Revision History

  • 4 August 2011 (me) Comprehensive update posted live
  • 16 November 2004 (me) Review posted to live Web site
  • 11 August 2004 (ac) Original submission
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