Hereditary Spastic Paraplegia Overview

Synonyms: Hereditary Spastic Paraparesis, Strumpell-Lorrain Syndrome

Hedera P.

Publication Details

Estimated reading time: 35 minutes

Summary

The purpose of this overview is to increase the awareness of clinicians regarding hereditary spastic paraplegia. The following are the goals of this overview.

Goal 1.

Describe the clinical characteristics of hereditary spastic paraplegia and recommended treatment.

Goal 2.

Review the causes of hereditary spastic paraplegia.

Goal 3.

Consider the differential diagnosis of hereditary spastic paraplegia.

Goal 4.

Provide an evaluation strategy to identify the genetic cause of hereditary spastic paraplegia in a proband.

Goal 5.

Inform genetic counseling of family members of a proband with hereditary spastic paraplegia.

1. Clinical Characteristics and Recommended Treatment: Hereditary Spastic Paraplegia

The predominant signs and symptoms of hereditary spastic paraplegia (HSP) are lower-extremity weakness and spasticity.

Neurologic examination. Individuals with HSP demonstrate the following:

  • Bilateral lower-extremity spasticity (maximal in hamstrings, quadriceps, adductors, and gastrocnemius-soleus muscles) and weakness (maximal in the iliopsoas, hamstring, and tibialis anterior muscles). Spasticity and weakness are variable. Some individuals have spasticity and no demonstrable weakness, whereas others have spasticity and weakness in approximately the same proportions.
  • Lower-extremity hyperreflexia and extensor plantar responses
  • Often, mildly impaired vibration sensation in the distal lower extremities

Symptom onset

  • Early onset. When symptoms begin in very early childhood, they may be non-progressive and resemble spastic diplegic cerebral palsy.
  • Later onset. When symptoms begin in later childhood or after they usually progress slowly and steadily. After a number of years, it is not usual for individuals with progressively worsening gait to experience a "functional plateau" (i.e., the rate of further worsening of gait impairment is similar to that attributable to age).

Classification. HSP is classified clinically as "uncomplicated" (nonsyndromic) or "complicated" (syndromic).

  • Uncomplicated (or "pure") HSP is characterized by neurologic impairment limited to progressive lower-extremity spastic weakness, hypertonic urinary bladder disturbance, and mild diminution of lower-extremity vibration sensation [Harding 1983]. Individuals with uncomplicated HSP experience the following:
    • Difficulty walking (may either be non-progressive or worsen insidiously)
    • Often, the need for canes, walkers, or wheelchairs
    • Possible urinary urgency and lower-extremity paresthesias
    • Typically, normal strength and dexterity of the upper extremities
    • No involvement of speech, chewing, or swallowing
    Though symptoms may be disabling, life span is not shortened.
  • Complicated HSP is characterized by the impairments present in uncomplicated HSP plus other system involvement or other neurologic findings including any of the following:*
    • Ataxia
    • Seizures
    • Intellectual disability
    • Dementia
    • Muscle atrophy
    • Extrapyramidal disturbance
    • Peripheral neuropathy
    * In the absence of other causes for these additional features

Treatment of Manifestations

At present, there is no specific treatment to prevent or reverse nerve degeneration in HSP. Treatments are directed at reducing symptoms and improving balance, strength, and agility. Individuals should be evaluated periodically (annually or as needed) by a neurologist and physiatrist to assess progression and develop treatment strategies to maximize walking ability and reduce symptoms.

Current recommendations:

  • Daily regimen of physical therapy directed toward improving cardiovascular fitness, maintaining and improving muscle strength and gait, and reducing spasticity
  • Occupational therapy, assistive walking devices, and ankle-foot orthotics as needed
  • Drugs to reduce muscle spasticity (e.g., Lioresal® [oral or intrathecal], tizanidine, dantrolene, botulinum A and B toxin injections [Botox®, Dysport, Xeomin, or Myoblock]) and urinary urgency (e.g., oxybutynin, solifenacin, mirabegron, or intrabladder injections with Botox®)

2. Causes of Hereditary Spastic Paraplegia

Genetic types of hereditary spastic paraplegia (HSP). To date, more than 80 genetic types of HSP have been defined by genetic linkage analysis and identification of HSP-related gene variants. In the past, genetic loci for HSP were designated SPG (for "spastic paraplegia") and numbered in order of their discovery. With the identification of the causative genes at those loci, reference by clinicians and clinical labs to a specific genetic type of HSP has moved to the name of the gene rather than the locus designation. Autosomal dominant, autosomal recessive, X-linked, and maternally inherited (mitochondrial) forms of HSP have been identified.

Autosomal dominant HSP is the most common type of HSP, found in 75%-80% of affected individuals.

  • SPG4, caused by a pathogenic variant in SPAST, is the most common type, accounting for approximately 40% of all autosomal dominant HSP.
  • SPG3A, caused by a pathogenic variant in ATL1, is the second most common type of autosomal dominant HSP, accounting for approximately 10%-15% of all autosomal dominant HSP. SPG3A is the main cause of autosomal dominant HSP with early onset (occurs in >75% of individuals in this category).
  • SPG30 (caused by a pathogenic variant in KIF1A) and SPG31 (caused by a pathogenic variant in REEP1) are both relatively common, each accounting for about 5% of all autosomal dominant HSP.
  • Other types of autosomal dominant HSP with a predominantly adult onset are relatively rare and most of them account for 1% or less of all autosomal dominant HSP.

Autosomal recessive HSP is very heterogeneous, with an ever-growing list of newly identified genes. Many new causes of autosomal recessive HSP are very rare and may be limited to a single family or even a single individual. The frequency is increased in populations with a higher degree of consanguinity. AR HSP is found in an estimated 25%-30% of all individuals with HSP.

Most common types of autosomal recessive HSP are encountered in the general population:

  • SPG5A, caused by pathogenic variants in CYP7B1, accounts for 7.3% of all autosomal recessive HSP and 3% of apparently sporadic pure spastic paraplegia.
  • SPG7, caused by pathogenic variants in SPG7, may account for approximately 5% of all autosomal recessive HSP.
  • SPG11, caused by pathogenic variants in SPG11, accounts for 3%-5% of all autosomal recessive HSP but is found in 75% of individuals with all types of HSP who have radiologic signs of thin or absent corpus callosum.

X-linked HSP and mitochondrial HSP are the rarest genetic forms of HSP, accounting for fewer than 1%-2% of all individuals affected with HSP.

Other. Several types of HSP (e.g., those associated with pathogenic variants in ATL1 [Khan et al 2014], SPG7 [McDermott et al 2001], and ALDH18A1 [Coutelier et al 2015]) may be inherited as either autosomal recessive or autosomal dominant disorders.

Table Icon

Table 1.

Hereditary Spastic Paraplegia: Genes and Distinguishing Clinical Features – Autosomal Dominant Inheritance

Table Icon

Table 2.

Hereditary Spastic Paraplegia: Genes and Distinguishing Clinical Features – Autosomal Recessive Inheritance

Table Icon

Table 3.

Hereditary Spastic Paraplegia: Genes and Distinguishing Clinical Features – X-Linked Inheritance

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Table 4.

Hereditary Spastic Paraplegia: Gene and Distinguishing Clinical Features – Maternal (Mitochondrial) Inheritance

3. Differential Diagnosis of Hereditary Spastic Paraplegia

The differential diagnosis includes the following:

4. Evaluation Strategies to Identify the Genetic Cause of Hereditary Spastic Paraplegia in a Proband

Establishing a specific genetic cause of hereditary spastic paraplegia (HSP):

  • Can aid in discussions of prognosis (which are beyond the scope of this GeneReview) and genetic counseling;
  • Usually involves a medical history, physical examination, laboratory testing, family history, and genomic/genetic testing.

Medical history and physical examination is directed at identifying neurologic features associated with HSP as well as any additional features that could indicate the presence of a complicated HSP (see Clinical Characteristics and Tables 1, 2, 3, and 4).

Family history includes a three-generation family history with attention to other relatives with possible HSP. Documentation of relevant findings in family members can be accomplished either through direct examination of those individuals or through review of their medical records including neuroimaging, neuropathology, neurologic examination, and results of molecular genetic testing. Autosomal dominant, autosomal recessive, and X-linked or maternal (mitochondrial) inheritance patterns have all been reported with HSP.

Exclusion of other disorders. See Differential Diagnosis.

Molecular genetic testing approaches can include a combination of gene-targeted testing (single-gene testing or multigene panel) and comprehensive genomic testing (exome sequencing, exome array). Gene-targeted testing requires the clinician to hypothesize which gene(s) are likely involved, whereas genomic testing does not.

  • Concurrent or serial single-gene testing can be considered if clinical findings and/or family history indicate that involvement of a particular gene or small subset of genes is most likely (see Tables 1, 2, 3, and 4).
  • A multigene panel that includes some or all of the genes listed in Table 1 is most likely to identify the genetic cause of the condition while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests.
    For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.
  • Comprehensive genomic testing (which does not require the clinician to determine which gene[s] are likely involved) may be considered. Exome sequencing is most commonly used; genome sequencing is also possible. Exome array (when clinically available) may be considered if exome sequencing is not diagnostic.
    For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.

5. Genetic Counseling

Genetic counseling is the process of providing individuals and families with information on the nature, mode(s) of 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; it is not meant to address all personal, cultural, or ethical issues that may arise or to substitute for consultation with a genetics professional. —ED.

Mode of Inheritance

Hereditary spastic paraplegia (HSP) can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner or by maternal (mitochondrial) inheritance, depending on the genetic subtype in a family.

Several types of HSP (e.g., those associated with pathogenic variants in ATL1, SPG7, ALDH18A1, and possibly SPG11) may be inherited either as autosomal recessive or autosomal dominant disorders (see Causes of Hereditary Spastic Paraplegia).

Risk to Family Members

Autosomal Dominant HSP

Parents of a proband

  • Most individuals diagnosed as having an autosomal dominant HSP have an affected parent.
  • Occasionally, a proband with HSP may have the disorder as the result of a de novo pathogenic variant. The frequency of de novo variants causing autosomal dominant HSP is unknown.
  • Recommendations for the evaluation of parents of a proband with an apparent de novo pathogenic variant include molecular genetic testing of both parents for the pathogenic variant identified in the proband.
  • If the pathogenic variant found in the proband cannot be detected in the leukocyte DNA of either parent, possible explanations include a de novo pathogenic variant in the proband or germline mosaicism in a parent. Parental germline mosaicism has been reported in SPAST-related HSP (SPG4) [Aulitzky et al 2014]. The incidence of parental germline mosaicism is probably very low, but no conclusive epidemiologic data are available.

Sibs of a proband

  • The risk to the sibs of the proband depends on the genetic status of the proband's parents: if one of the proband's parents has a pathogenic variant, the risk to the sibs of inheriting the pathogenic variant is 50%.
  • The age of onset and degree of disability are highly variable among members of the same family, in different families with the same pathogenic variant, or between genetic types of HSP.
  • If the HSP-related pathogenic variant found in the proband cannot be detected in the leukocyte DNA of either parent, the risk to sibs is slightly greater than that of the general population (though still <1%) because of the theoretic possibility of parental germline mosaicism.

Offspring of a proband. Each child of an individual with autosomal dominant HSP is at a 50% risk of inheriting the HSP-related pathogenic variant.

Other family members. The risk to other family members depends on the status of the proband's parents: if a parent is affected, the parent's family members may be at risk.

Autosomal Recessive HSP

Parents of a proband

  • The parents of an affected individual are obligate heterozygotes (i.e., carriers of one HSP-related pathogenic variant).
  • Heterozygotes (carriers) are typically asymptomatic. The only known exception to this rule is SPG7, where an apparently dominant inheritance was suggested for otherwise autosomal recessive HSP [McDermott et al 2001].

Sibs of a proband

  • At conception, each sib 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.
  • Heterozygotes are typically asymptomatic if the pattern of inheritance is consistent with autosomal recessive mode and affected individuals harbor biallelic pathogenic variants.

Offspring of a proband. The offspring of an individual with autosomal recessive HSP are obligate heterozygotes (carriers) for an HSP-related pathogenic variant.

Other family members. Each sib of the proband's parents is at a 50% risk of being a carrier of an HSP-related pathogenic variant.

X-Linked HSP

Parents of a male proband

  • The father of an affected male will not have the disorder nor will he be hemizygous for the HSP-related pathogenic variant; therefore, he does not require further evaluation/testing.
  • In a family with more than one individual with X-linked HSP, the mother of an affected male is an obligate carrier of the HSP-related pathogenic variant. If a woman has more than one affected child and if the HSP-related pathogenic variant cannot be detected in her leukocyte DNA, she most likely has germline mosaicism (maternal germline and somatic mosaicism in L1CAM-related HSP [SPG1] has been reported [Du et al 1998, Vits et al 1998]).
  • If a male is the only affected family member (i.e., a simplex case), the mother may be a heterozygote or the affected male may have a de novo HSP-related pathogenic variant, in which case the mother is not a heterozygote.

Parents of a female proband

  • A female proband may have inherited the HSP-related pathogenic variant from either her mother or her father, or the pathogenic variant may be de novo.
  • Detailed evaluation of the parents and review of the extended family history may help distinguish probands with a de novo pathogenic variant from those with an inherited pathogenic variant. Molecular genetic testing of the mother (and possibly the father, or subsequently the father) can determine if the pathogenic variant was inherited.

Sibs of a male proband

  • The risk to sibs depends on the genetic status of the mother.
    • If the mother of the proband with X-linked HSP has an HSP-related pathogenic variant, the chance of transmitting it in each pregnancy is 50%. Males who inherit the variant will be affected; females who inherit the variant will be heterozygotes and may have a range of clinical manifestations (see Table 3).
    • If the proband represents a simplex case (i.e., a single occurrence in a family) and if the HSP-related pathogenic variant cannot be detected in the leukocyte DNA of the mother, the risk to sibs is slightly greater than that of the general population (though still <1%) because of the theoretic possibility of maternal germline mosaicism.
  • The age of onset, penetrance, and degree of disability are not predictable in members of the same family, in different families with the same pathogenic variant, or between genetic types of HSP.

Sibs of a female proband

  • The risk to sibs depends on the genetic status of the parents.
    • If the mother of the proband has an HSP-related pathogenic variant, the chance of transmitting it in each pregnancy is 50%. Males who inherit the variant will be affected; females who inherit the variant will be heterozygotes and may have a range of clinical manifestations (see Table 3).
    • If the father of the proband has an HSP-related pathogenic variant, he will transmit it to all of his daughters and none of his sons.
  • If the proband represents a simplex case (i.e., a single occurrence in a family) and if the HSP-related pathogenic variant cannot be detected in the leukocyte DNA of either parent, the risk to sibs is slightly greater than that of the general population (though still <1%) because of the possibility of parental germline mosaicism.
  • The age of onset, penetrance, and degree of disability are not predictable in members of the same family, in different families with the same pathogenic variant, or between genetic types of HSP.

Offspring of a male proband. Affected males transmit the HSP-related pathogenic variant to:

  • All of their daughters, who will be heterozygotes and may have a range of clinical manifestations (see Table 3);
  • None of their sons.

Offspring of a female proband. Women with an HSP-related pathogenic variant have a 50% chance of transmitting the pathogenic variant to each child:

  • Males who inherit the pathogenic variant will be affected.
  • Females who inherit the variant will be heterozygotes and may have a range of clinical manifestations (see Table 3). This is best documented for SPG2, where female heterozygotes may show a mild paraparesis with late onset of the disease [Sivakumar et al 1999].

Other family members. The risk to other family members depends on the status of the proband's parents: if a parent has the HSP-related pathogenic variant, the parent's family members may be at risk.

Heterozygote (carrier) detection. Molecular genetic testing of at-risk female relatives to determine their genetic status is most informative if the pathogenic variant has been identified in the proband.

Note:

(1) Females who are heterozygous for X-linked HSP may have a range of clinical manifestations (see Table 3).

(2) Identification of female heterozygotes requires either (a) prior identification of the HSP-related pathogenic variant in the family or, (b) if an affected male is not available for testing, molecular genetic testing first by sequence analysis, and if no pathogenic variant is identified, by gene-targeted deletion/duplication analysis.

Maternal (Mitochondrial) Inheritance

Parents of a proband

  • The father of a proband is not at risk of having the MT-ATP6 pathogenic variant.
  • The mother of a proband (usually) has the MT-ATP6 pathogenic variant and may or may not have symptoms.
  • Alternatively, the proband may have a de novo (somatic) mitochondrial pathogenic variant.

Sibs of a proband

  • The risk to the sibs depends on the genetic status of the mother.
  • If the mother has the MT-ATP6 pathogenic variant, all sibs of a proband will inherit the MT-ATP6 pathogenic variant and may or may not have symptoms.

Offspring of a proband

  • All offspring of females with a mtDNA pathogenic variant will inherit the pathogenic variant.
  • Offspring of males with a mtDNA pathogenic variant are not at risk of inheriting the pathogenic variant.

Other family members. The risk to other family members depends on the genetic status of the proband's mother. If the mother has an MT-ATP6 pathogenic variant, her sibs and mother are also at risk.

Related Genetic Counseling Issues

Caution must be exercised when counseling an individual who has all the signs and symptoms of HSP but no similarly affected relatives. Such individuals may be diagnosed as having primary lateral sclerosis (PLS). While such individuals with no known family history of HSP may have autosomal recessive HSP (and thus low risk of transmitting the disorder to offspring), it is also possible that they have X-linked HSP, autosomal dominant HSP with reduced penetrance, a de novo pathogenic variant, a mtDNA pathogenic variant, mistaken paternity, or an environmentally acquired disorder.

Family planning

  • The optimal time for determination of genetic risk and discussion of the availability of prenatal/preimplantation genetic testing is before pregnancy. Similarly, decisions about testing to determine the genetic status of at-risk asymptomatic family members are best made before pregnancy.
  • It is appropriate to offer genetic counseling (including general discussion of potential risks to offspring and reproductive options) to young adults who are affected, carriers, or at risk of being affected or a carrier; however, it is not possible to make specific predictions about the potential severity of disease in offspring.

DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown). For more information, see Huang et al [2022].

Prenatal Testing and Preimplantation Genetic Testing

Once the pathogenic variant(s) have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing for hereditary spastic paraplegia are possible.

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.

Chapter Notes

Author History

John K Fink, MD; University of Michigan (2000-2018)
Peter Hedera, MD, PhD, FACMG (2018-present)

Revision History

  • 11 February 2021 (aa/ha/ph) Revision: added AD SPG30 and associated references; updated SPG1/MASA syndrome terminology information
  • 27 September 2018 (ha) Comprehensive update posted live
  • 6 February 2014 (me) Comprehensive update posted live
  • 3 February 2009 (cd) Revision: sequence analysis for SPG5A available clinically
  • 21 May 2008 (cd) Revision: pathogenic variants in ZFYVE26 identified as causative of SPG15
  • 4 March 2008 (cd) Revision: sequence analysis of entire coding region available for SPG8 and SPG33
  • 4 October 2007 (cd) Revision: sequence analysis for SPG10 available on a clinical basis
  • 11 July 2007 (me) Comprehensive update posted live
  • 21 October 2004 (cd) Revision: arginase deficiency added
  • 26 February 2004 (cd) Revision: testing for SPG6 clinically available
  • 15 October 2003 (cd) Revision: test availability
  • 22 September 2003 (me) Comprehensive update posted live
  • 15 August 2000 (me) Overview posted live
  • 21 March 2000 (jf) Original submission

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