🔗

Mappings

MONDO

MONDO:0011803 hereditary spastic paraplegia 7

👪

Inheritance

1

Autosomal recessive HP:0000007

SPG7-related neurologic disorder is inherited in an autosomal recessive manner. Several studies have reported a single heterozygous SPG7 variant in affected individuals, raising the possibility of autosomal dominant inheritance, but that possibility remains controversial and is not curated here as an established mode. Where both parents are known heterozygotes, each sib of a proband has a 25% chance of being affected at conception.

autosomal recessive inheritance

Show evidence (3 references)

PMID:20301286 SUPPORT Human Clinical

"SPG7-related neurologic disorder is inherited in an autosomal recessive manner."

States the established mode of inheritance.

PMID:20301286 SUPPORT Human Clinical

"however, the possibility of autosomal dominant inheritance remains controversial"

Records the unresolved monoallelic question. Classified PARTIAL because the source explicitly declines to settle it, and this entry therefore does not curate a dominant inheritance block.

PMID:20301286 SUPPORT Human Clinical

"If both parents are known to be heterozygous for an SPG7 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being heterozygous, and a 25% chance of inheriting neither of the familial pathogenic variants."

GeneReviews genetic-counseling statement supplying the recurrence risk for sibs of a proband. Cited separately from the mode-of-inheritance snippet above because a transmission figure is a distinct quantitative claim.

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Pathophysiology

5

Paraplegin Loss and m-AAA Protease Deficiency

Biallelic SPG7 variants abolish paraplegin, a nuclear-encoded mitochondrial metalloprotease that localizes to mitochondria and is highly homologous to the yeast inner-membrane ATPases AFG3, RCA1, and YME1, which carry both proteolytic and chaperone-like activities. In its metazoan role, paraplegin is a subunit of the m-AAA protease family responsible for degrading oxidatively damaged and misfolded mitochondrial proteins. Loss of this quality-control protease is the entry point of the disorder, and it places SPG7 in the mitochondrial-function category of HSP genes alongside SPG13/HSPD1.

SPG7 hgnc:11237

mitochondrial protein quality control GO:0141164 ⇓ LOSS OF FUNCTION

Downstream

Mitochondrial Dysfunction and OXPHOS Impairment Without the quality-control protease, damaged mitochondrial proteins are not cleared and respiratory function falls.

Show evidence (4 references)

PMID:9635427 SUPPORT Human Clinical

"We found that patients from a chromosome 16q24.3-linked HSP family are homozygous for a 9.5 kb deletion involving a gene encoding a novel protein, named Paraplegin."

The original identification of biallelic SPG7/paraplegin loss as the cause, in human HSP families.

PMID:9635427 SUPPORT In Vitro

"Paraplegin is highly homologous to the yeast mitochondrial ATPases, AFG3, RCA1, and YME1, which have both proteolytic and chaperon-like activities at the inner mitochondrial membrane. Immunofluorescence analysis and import experiments showed that Paraplegin localizes to mitochondria."

Establishes the molecular identity and subcellular localization of the lost protein. Evidence source is IN_VITRO because the localization rests on immunofluorescence and import experiments.

PMID:29467464 SUPPORT Model Organism

"we have created a CRISPR/Cas9 allele of the Drosophila homolog of SPG7, which encodes an inner membrane-localized AAA+ protease known as paraplegin"

Confirms paraplegin's identity as an inner-membrane AAA+ protease in a metazoan and supplies the model system used below. Evidence source is MODEL_ORGANISM because the work is in Drosophila.

+ 1 more reference

Mitochondrial Dysfunction and OXPHOS Impairment

Loss of the m-AAA protease leaves oxidatively damaged and misfolded mitochondrial proteins uncleared, and oxidative phosphorylation fails. This was demonstrable in human tissue from the outset: muscle biopsies from two of the original paraplegin-mutant patients showed typical signs of mitochondrial OXPHOS defects. The Drosophila SPG7 null recapitulates the mitochondrial phenotype in detail, with reduced respiratory chain complex I and II activities, electron-dense matrix accumulation, and severely swollen and dysmorphic mitochondria.

oxidative phosphorylation GO:0006119 ↓ DECREASED mitochondrion organization GO:0007005 ⚠ ABNORMAL

Downstream

Impaired Axonal Mitochondrial Transport and Distal Synaptic Failure Dysfunctional mitochondria are also mistransported along the axon, so the distal compartment is worst supplied.

Show evidence (2 references)

PMID:9635427 SUPPORT Human Clinical

"Analysis of muscle biopsies from two patients carrying Paraplegin mutations showed typical signs of mitochondrial OXPHOS defects, thus suggesting a mechanism for neurodegeneration in HSP-type disorders."

Direct human tissue evidence for OXPHOS impairment in paraplegin-mutant patients, which is why this node is not a model-only claim.

PMID:29467464 SUPPORT Model Organism

"A variety of mitochondrial defects accompanied the degenerative phenotypes of SPG7 mutants, including altered axonal transport of mitochondria, accumulation of electron-dense material in the matrix of flight muscle mitochondria, reduced activities of respiratory chain complexes I and II, and..."

Enumerates the mitochondrial defects in the null model, including the altered axonal transport of mitochondria that is the edge to the next node.

Impaired Axonal Mitochondrial Transport and Distal Synaptic Failure

Beyond the bioenergetic deficit itself, mitochondrial transport along the axon is disturbed, so the distal axon and its terminal are the compartment least well supplied with functional mitochondria. Ultrastructural examination of Drosophila SPG7-null photoreceptors localizes the start of the neurodegenerative process to the synaptic terminal rather than the cell body, which is the model-level correlate of the dying-back pattern seen clinically. This is a model-organism claim about where degeneration begins; the human evidence for SPG7 establishes the OXPHOS lesion and the tract degeneration but not the subcellular sequence.

axonal transport of mitochondrion GO:0019896 ⚠ ABNORMAL

Downstream

Corticospinal and Cerebellar Degeneration Distal supply failure kills the longest and most metabolically exposed central axons first.

Show evidence (2 references)

PMID:29467464 SUPPORT Model Organism

"Ultrastructural examination of photoreceptor neurons indicated that the neurodegenerative phenotype of SPG7 mutants initiates at the synaptic terminal."

Localizes the onset of degeneration to the distal compartment, the subcellular basis for the dying-back pattern. Evidence source is MODEL_ORGANISM because the observation is in Drosophila photoreceptors.

PMID:29467464 SUPPORT Model Organism

"Drosophila SPG7 mutants exhibited shortened lifespan, progressive locomotor defects, sensitivity to chemical and environmental stress, and muscular and neuronal degeneration."

Establishes that the null allele produces progressive locomotor decline and neuronal degeneration, i.e. that the mitochondrial lesion is sufficient for the degenerative phenotype in this model.

Corticospinal and Cerebellar Degeneration

The corticospinal axons degenerate, producing the progressive bilateral leg weakness and spasticity that names the disorder. Unlike most HSP genes, however, SPG7 produces cerebellar degeneration in parallel and often in equal or greater measure, so ataxia, dysarthria, and dysphagia may be the presenting features rather than spasticity. Optic nerve degeneration is a third target, and isolated optic atrophy is a recognized presentation of the same genotype.

cortical motor neuron CL:0000598 cerebellar Purkinje cell CL:0000121

neuron projection maintenance GO:1990535 ↓ DECREASED

corticospinal tract UBERON:0002707 cerebellum UBERON:0002037

Downstream

Progressive Spastic Ataxia Combined corticospinal and cerebellar degeneration produces the mixed spastic-ataxic syndrome characteristic of SPG7.

Show evidence (2 references)

PMID:9635427 SUPPORT Other

"Hereditary spastic paraplegia (HSP) is characterized by progressive weakness and spasticity of the lower limbs due to degeneration of corticospinal axons."

The class-level statement that HSP weakness and spasticity arise from corticospinal axon degeneration. Evidence source is OTHER because this is a background statement about the disease class rather than a finding of the study.

PMID:20301286 SUPPORT Human Clinical

"Initially the spastic paraplegia is typically characterized by insidiously progressive bilateral leg weakness and spasticity or cerebellar findings (ataxia, dysarthria, and dysphagia) or both."

Supports the parallel corticospinal and cerebellar involvement that distinguishes SPG7 from a pure corticospinal HSP.

Progressive Spastic Ataxia

The clinical endpoint is a phenotypic spectrum rather than a single syndrome: uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar ataxia, and isolated optic nerve atrophy are all recognized presentations of biallelic SPG7 variants. Onset is typically adult but ranges from infancy to age 72. Spasticity and ataxia are progressive and may result in wheelchair dependence. Additional central features include decreased visual acuity from optic neuropathy, cognitive impairment, and dystonia, and there is a peripheral nervous system arm with motor and sensory neuropathy, neuropathic pain, and amyotrophy.

Show evidence (2 references)

PMID:20301286 SUPPORT Human Clinical

"The phenotypic spectrum of SPG7-related neurologic disorder includes uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar ataxia, and isolated optic nerve atrophy."

Establishes that this endpoint is a spectrum of four recognized presentations, which is why the node does not assert a single syndrome.

PMID:20301286 SUPPORT Human Clinical

"Although onset typically occurs in adulthood, it may start in infancy or as late as age 72 years."

Supplies the age-of-onset range recorded in this node.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

14

Digestive 1

Dysphagia HP:0002015

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"cerebellar findings (ataxia, dysarthria, and dysphagia)"

Dysphagia is part of the cerebellar component of SPG7.

Eye 1

Optic atrophy HP:0000648

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Other central nervous system findings include decreased visual acuity due to optic neuropathy, cognitive impairment, and dystonia."

Optic neuropathy is an established central feature of SPG7.

Limbs 1

Pes cavus HP:0001761

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Associated musculoskeletal involvement includes pes cavus and scoliosis."

Pes cavus is an associated musculoskeletal feature of SPG7.

Musculoskeletal 2

Scoliosis HP:0002650

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Associated musculoskeletal involvement includes pes cavus and scoliosis."

Scoliosis is an associated musculoskeletal feature of SPG7.

Amyotrophy Skeletal muscle atrophy HP:0003202

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Peripheral nervous system involvement manifests as motor and sensory neuropathy, neuropathic pain, and amyotrophy."

Amyotrophy is named explicitly in the GeneReviews peripheral-involvement sentence already cited in this entry. The preferred_term keeps the clinical word "amyotrophy" that the source uses, since the HPO label is the broader "Skeletal muscle atrophy".

Nervous System 5

Ataxia HP:0001251

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"bilateral leg weakness and spasticity or cerebellar findings (ataxia, dysarthria, and dysphagia) or both"

Cerebellar findings are an alternative or additional presenting manifestation.

Dysarthria HP:0001260

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"cerebellar findings (ataxia, dysarthria, and dysphagia)"

Dysarthria is part of the cerebellar component of SPG7.

Cognitive impairment HP:0100543

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Other central nervous system findings include decreased visual acuity due to optic neuropathy, cognitive impairment, and dystonia."

Cognitive impairment is an established central feature of SPG7.

Dystonia HP:0001332

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"optic neuropathy, cognitive impairment, and dystonia"

Dystonia is an established central feature of SPG7.

Peripheral neuropathy HP:0009830

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Peripheral nervous system involvement manifests as motor and sensory neuropathy, neuropathic pain, and amyotrophy."

Establishes the peripheral arm, which is curated separately from the central corticospinal arm because the two belong to different mechanism modules.

Constitutional 1

Neuropathic pain HP:0012531

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Peripheral nervous system involvement manifests as motor and sensory neuropathy, neuropathic pain, and amyotrophy."

Neuropathic pain is named in the same GeneReviews sentence, which this entry previously mined only for the neuropathy itself. Bound to the broader HP:0012531 Pain: the specific term HP:6000040 Neuropathic pain exists but is not a member of the PhenotypeTerm dynamic enum, so the preferred_term carries the specificity the ontology binding cannot.

Other 3

Spastic ataxia HP:0002497

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"The phenotypic spectrum of SPG7-related neurologic disorder includes uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar ataxia, and isolated optic nerve atrophy."

Spastic ataxia is the leading presentation of the SPG7 spectrum.

Lower limb spasticity HP:0002061

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Initially the spastic paraplegia is typically characterized by insidiously progressive bilateral leg weakness and spasticity"

The corticospinal component of the SPG7 phenotype.

Loss of ambulation HP:0002505

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"Spasticity and ataxia are progressive and may result in wheelchair dependence."

The source says "may result", so no frequency band is asserted for this phenotype.

🧬

Genetic Associations

1

SPG7 pathogenic variants (Causative)

Gene: SPG7 hgnc:11237 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:9635427 SUPPORT Human Clinical

"Two additional Paraplegin mutations, both resulting in a frameshift, were found in a complicated and in a pure form of HSP."

Documents both the loss-of-function mechanism and the pure/complicated phenotypic breadth present from the gene's first description.

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Medical Actions

1

Multidisciplinary Supportive Care

Action: Supportive Care NCIT:C15747

There is no disease-modifying therapy. Management is multidisciplinary care by specialists in neurology, ophthalmology, low vision services, audiology, urology, physiatry, occupational therapy, physical therapy, orthopedics, feeding therapy and nutrition, speech-language therapy, social work, psychology, and clinical genetics, with routinely scheduled surveillance for emerging manifestations.

Show evidence (2 references)

PMID:20301286 SUPPORT Human Clinical

"Treatment of manifestations: Multidisciplinary care by specialists in neurology, ophthalmology, low vision services, audiology, urology, physiatry, occupational therapy, physical therapy, orthopedics, feeding therapy and nutrition, speech-language therapy, social work, psychology, and clinical genetics."

The published management recommendation, curated as supportive because no disease-modifying option is offered.

PMID:20301286 SUPPORT Human Clinical

"Surveillance: Monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations with routinely scheduled evaluations by treating specialists."

Backs the surveillance clause in this treatment's description, which was previously a paraphrase with no evidence item behind it.

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Diagnosis

1

Molecular genetic testing for SPG7

The diagnosis is confirmed by identifying biallelic pathogenic SPG7 variants in a proband with suggestive findings. Because the phenotypic spectrum spans spastic ataxia, pure spinocerebellar ataxia and isolated optic atrophy, the suggestive findings that prompt testing are broader than a spastic paraparesis alone.

genetic testing NCIT:C15709

Show evidence (1 reference)

PMID:20301286 SUPPORT Human Clinical

"The diagnosis of SPG7-related neurologic disorder is established in a proband with suggestive findings and biallelic pathogenic variants in SPG7 identified by molecular genetic testing."

The GeneReviews confirmatory-testing criterion. Note it says "suggestive findings" rather than naming a syndrome, consistent with the breadth of the SPG7 phenotypic spectrum this entry curates.

{ }

Source YAML

click to show

name: Hereditary Spastic Paraplegia 7
creation_date: "2026-08-22T00:00:00Z"
category: Mendelian
synonyms:
- SPG7
- spastic paraplegia 7
- SPG7-related neurologic disorder
- hereditary spastic paraplegia paraplegin type
- spastic paraplegia 7, autosomal recessive
description: >-
  Hereditary spastic paraplegia 7 (SPG7) is caused by biallelic variants in SPG7,
  which encodes paraplegin, a nuclear-encoded subunit of the m-AAA metalloprotease
  of the inner mitochondrial membrane. The m-AAA complex has both proteolytic and
  chaperone-like activity and is responsible for the selective degradation of
  oxidatively damaged and misfolded mitochondrial proteins; its loss produces
  oxidative phosphorylation impairment, which was demonstrable in muscle biopsies
  from the very first patients in whom paraplegin mutations were identified. The
  clinical phenotype is broader than the SPG designation suggests: it spans
  uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar
  ataxia, and isolated optic atrophy, so SPG7 belongs to the hereditary ataxia
  differential as much as to the spastic paraplegia one. Onset is typically in
  adulthood but ranges from infancy to age 72.
disease_term:
  preferred_term: hereditary spastic paraplegia 7
  term:
    id: MONDO:0011803
    label: hereditary spastic paraplegia 7
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0011803
      label: hereditary spastic paraplegia 7
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
parents:
- Hereditary Spastic Paraplegia
- Hereditary Ataxia
- Mitochondrial Disease
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    SPG7-related neurologic disorder is inherited in an autosomal recessive
    manner. Several studies have reported a single heterozygous SPG7 variant in
    affected individuals, raising the possibility of autosomal dominant
    inheritance, but that possibility remains controversial and is not curated
    here as an established mode. Where both parents are known heterozygotes,
    each sib of a proband has a 25% chance of being affected at conception.
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SPG7-related neurologic disorder is inherited in an autosomal recessive
      manner.
    explanation: States the established mode of inheritance.
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      however, the possibility of autosomal dominant inheritance remains
      controversial
    explanation: >-
      Records the unresolved monoallelic question. Classified PARTIAL because the
      source explicitly declines to settle it, and this entry therefore does not
      curate a dominant inheritance block.
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If both parents are known to be heterozygous for an SPG7 pathogenic
      variant, each sib of an affected individual has at conception a 25% chance
      of being affected, a 50% chance of being heterozygous, and a 25% chance of
      inheriting neither of the familial pathogenic variants.
    explanation: >-
      GeneReviews genetic-counseling statement supplying the recurrence risk for
      sibs of a proband. Cited separately from the mode-of-inheritance snippet
      above because a transmission figure is a distinct quantitative claim.
pathophysiology:
- name: Paraplegin Loss and m-AAA Protease Deficiency
  conforms_to: "corticospinal_tract_axonopathy#Long-Axon Maintenance Machinery Defect"
  biological_scale: MOLECULAR
  description: >-
    Biallelic SPG7 variants abolish paraplegin, a nuclear-encoded mitochondrial
    metalloprotease that localizes to mitochondria and is highly homologous to the
    yeast inner-membrane ATPases AFG3, RCA1, and YME1, which carry both
    proteolytic and chaperone-like activities. In its metazoan role, paraplegin
    is a subunit of the m-AAA protease family responsible for degrading
    oxidatively damaged and misfolded mitochondrial proteins. Loss of this
    quality-control protease is the entry point of the disorder, and it places
    SPG7 in the mitochondrial-function category of HSP genes alongside
    SPG13/HSPD1.
  gene:
    preferred_term: SPG7
    term:
      id: hgnc:11237
      label: SPG7
  biological_processes:
  - preferred_term: mitochondrial protein quality control
    term:
      id: GO:0141164
      label: mitochondrial protein quality control
    modifier: LOSS_OF_FUNCTION
  evidence:
  - reference: PMID:9635427
    reference_title: "Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We found that patients from a chromosome 16q24.3-linked HSP family are
      homozygous for a 9.5 kb deletion involving a gene encoding a novel protein,
      named Paraplegin.
    explanation: >-
      The original identification of biallelic SPG7/paraplegin loss as the cause,
      in human HSP families.
  - reference: PMID:9635427
    reference_title: "Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Paraplegin is highly homologous to the yeast mitochondrial ATPases, AFG3,
      RCA1, and YME1, which have both proteolytic and chaperon-like activities at
      the inner mitochondrial membrane. Immunofluorescence analysis and import
      experiments showed that Paraplegin localizes to mitochondria.
    explanation: >-
      Establishes the molecular identity and subcellular localization of the lost
      protein. Evidence source is IN_VITRO because the localization rests on
      immunofluorescence and import experiments.
  - reference: PMID:29467464
    reference_title: "Loss of the Drosophila m-AAA mitochondrial protease paraplegin results in mitochondrial dysfunction, shortened lifespan, and neuronal and muscular degeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we have created a CRISPR/Cas9 allele of the Drosophila homolog of SPG7,
      which encodes an inner membrane-localized AAA+ protease known as paraplegin
    explanation: >-
      Confirms paraplegin's identity as an inner-membrane AAA+ protease in a
      metazoan and supplies the model system used below. Evidence source is
      MODEL_ORGANISM because the work is in Drosophila.
  - reference: PMID:29467464
    reference_title: "Loss of the Drosophila m-AAA mitochondrial protease paraplegin results in mitochondrial dysfunction, shortened lifespan, and neuronal and muscular degeneration."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      To oppose this occurrence, organisms employ a variety of strategies,
      including the selective degradation of oxidatively damaged and misfolded
      mitochondrial proteins.
    explanation: >-
      Supports this node's functional claim, and the GO mitochondrial
      protein quality control binding, that the m-AAA protease family degrades
      oxidatively damaged and misfolded mitochondrial proteins. Evidence source
      is OTHER because this is the review-style framing of the paper rather than
      its own experimental result.
  downstream:
  - target: Mitochondrial Dysfunction and OXPHOS Impairment
    description: >-
      Without the quality-control protease, damaged mitochondrial proteins are
      not cleared and respiratory function falls.

- name: Mitochondrial Dysfunction and OXPHOS Impairment
  biological_scale: CELLULAR
  description: >-
    Loss of the m-AAA protease leaves oxidatively damaged and misfolded
    mitochondrial proteins uncleared, and oxidative phosphorylation fails. This
    was demonstrable in human tissue from the outset: muscle biopsies from two of
    the original paraplegin-mutant patients showed typical signs of mitochondrial
    OXPHOS defects. The Drosophila SPG7 null recapitulates the mitochondrial
    phenotype in detail, with reduced respiratory chain complex I and II
    activities, electron-dense matrix accumulation, and severely swollen and
    dysmorphic mitochondria.
  biological_processes:
  - preferred_term: oxidative phosphorylation
    term:
      id: GO:0006119
      label: oxidative phosphorylation
    modifier: DECREASED
  - preferred_term: mitochondrion organization
    term:
      id: GO:0007005
      label: mitochondrion organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:9635427
    reference_title: "Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Analysis of muscle biopsies from two patients carrying Paraplegin mutations
      showed typical signs of mitochondrial OXPHOS defects, thus suggesting a
      mechanism for neurodegeneration in HSP-type disorders.
    explanation: >-
      Direct human tissue evidence for OXPHOS impairment in paraplegin-mutant
      patients, which is why this node is not a model-only claim.
  - reference: PMID:29467464
    reference_title: "Loss of the Drosophila m-AAA mitochondrial protease paraplegin results in mitochondrial dysfunction, shortened lifespan, and neuronal and muscular degeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      A variety of mitochondrial defects accompanied the degenerative phenotypes
      of SPG7 mutants, including altered axonal transport of mitochondria,
      accumulation of electron-dense material in the matrix of flight muscle
      mitochondria, reduced activities of respiratory chain complexes I and II,
      and severely swollen and dysmorphic mitochondria in the synaptic terminals
      of photoreceptors.
    explanation: >-
      Enumerates the mitochondrial defects in the null model, including the
      altered axonal transport of mitochondria that is the edge to the next node.
  downstream:
  - target: Impaired Axonal Mitochondrial Transport and Distal Synaptic Failure
    description: >-
      Dysfunctional mitochondria are also mistransported along the axon, so the
      distal compartment is worst supplied.

- name: Impaired Axonal Mitochondrial Transport and Distal Synaptic Failure
  conforms_to: "corticospinal_tract_axonopathy#Impaired Axonal Transport and Organelle Distribution"
  biological_scale: CELLULAR
  description: >-
    Beyond the bioenergetic deficit itself, mitochondrial transport along the axon
    is disturbed, so the distal axon and its terminal are the compartment least
    well supplied with functional mitochondria. Ultrastructural examination of
    Drosophila SPG7-null photoreceptors localizes the start of the
    neurodegenerative process to the synaptic terminal rather than the cell body,
    which is the model-level correlate of the dying-back pattern seen clinically.
    This is a model-organism claim about where degeneration begins; the human
    evidence for SPG7 establishes the OXPHOS lesion and the tract degeneration
    but not the subcellular sequence.
  biological_processes:
  - preferred_term: axonal transport of mitochondrion
    term:
      id: GO:0019896
      label: axonal transport of mitochondrion
    modifier: ABNORMAL
  evidence:
  - reference: PMID:29467464
    reference_title: "Loss of the Drosophila m-AAA mitochondrial protease paraplegin results in mitochondrial dysfunction, shortened lifespan, and neuronal and muscular degeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Ultrastructural examination of photoreceptor neurons indicated that the
      neurodegenerative phenotype of SPG7 mutants initiates at the synaptic
      terminal.
    explanation: >-
      Localizes the onset of degeneration to the distal compartment, the
      subcellular basis for the dying-back pattern. Evidence source is
      MODEL_ORGANISM because the observation is in Drosophila photoreceptors.
  - reference: PMID:29467464
    reference_title: "Loss of the Drosophila m-AAA mitochondrial protease paraplegin results in mitochondrial dysfunction, shortened lifespan, and neuronal and muscular degeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Drosophila SPG7 mutants exhibited shortened lifespan, progressive locomotor
      defects, sensitivity to chemical and environmental stress, and muscular and
      neuronal degeneration.
    explanation: >-
      Establishes that the null allele produces progressive locomotor decline and
      neuronal degeneration, i.e. that the mitochondrial lesion is sufficient for
      the degenerative phenotype in this model.
  downstream:
  - target: Corticospinal and Cerebellar Degeneration
    description: >-
      Distal supply failure kills the longest and most metabolically exposed
      central axons first.

- name: Corticospinal and Cerebellar Degeneration
  conforms_to: "corticospinal_tract_axonopathy#Distal Length-Dependent Degeneration of Long CNS Axons"
  biological_scale: TISSUE
  description: >-
    The corticospinal axons degenerate, producing the progressive bilateral leg
    weakness and spasticity that names the disorder. Unlike most HSP genes,
    however, SPG7 produces cerebellar degeneration in parallel and often in
    equal or greater measure, so ataxia, dysarthria, and dysphagia may be the
    presenting features rather than spasticity. Optic nerve degeneration is a
    third target, and isolated optic atrophy is a recognized presentation of the
    same genotype.
  cell_types:
  - preferred_term: cortical motor neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  - preferred_term: cerebellar Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  biological_processes:
  - preferred_term: neuron projection maintenance
    term:
      id: GO:1990535
      label: neuron projection maintenance
    modifier: DECREASED
  locations:
  - preferred_term: corticospinal tract
    term:
      id: UBERON:0002707
      label: corticospinal tract
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  evidence:
  - reference: PMID:9635427
    reference_title: "Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hereditary spastic paraplegia (HSP) is characterized by progressive
      weakness and spasticity of the lower limbs due to degeneration of
      corticospinal axons.
    explanation: >-
      The class-level statement that HSP weakness and spasticity arise from
      corticospinal axon degeneration. Evidence source is OTHER because this is a
      background statement about the disease class rather than a finding of the
      study.
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Initially the spastic paraplegia is typically characterized by insidiously
      progressive bilateral leg weakness and spasticity or cerebellar findings
      (ataxia, dysarthria, and dysphagia) or both.
    explanation: >-
      Supports the parallel corticospinal and cerebellar involvement that
      distinguishes SPG7 from a pure corticospinal HSP.
  downstream:
  - target: Progressive Spastic Ataxia
    description: >-
      Combined corticospinal and cerebellar degeneration produces the mixed
      spastic-ataxic syndrome characteristic of SPG7.

- name: Progressive Spastic Ataxia
  conforms_to: "corticospinal_tract_axonopathy#Progressive Lower-Limb Spasticity and Weakness"
  biological_scale: ORGANISM
  description: >-
    The clinical endpoint is a phenotypic spectrum rather than a single syndrome:
    uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar
    ataxia, and isolated optic nerve atrophy are all recognized presentations of
    biallelic SPG7 variants. Onset is typically adult but ranges from infancy to
    age 72. Spasticity and ataxia are progressive and may result in wheelchair
    dependence. Additional central features include decreased visual acuity from
    optic neuropathy, cognitive impairment, and dystonia, and there is a
    peripheral nervous system arm with motor and sensory neuropathy, neuropathic
    pain, and amyotrophy.
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotypic spectrum of SPG7-related neurologic disorder includes
      uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar
      ataxia, and isolated optic nerve atrophy.
    explanation: >-
      Establishes that this endpoint is a spectrum of four recognized
      presentations, which is why the node does not assert a single syndrome.
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Although onset typically occurs in adulthood, it may start in infancy or as
      late as age 72 years.
    explanation: Supplies the age-of-onset range recorded in this node.
phenotypes:
- name: Spastic ataxia
  category: Neurologic
  description: >-
    The characteristic combination of corticospinal spasticity and cerebellar
    ataxia that defines the commonest SPG7 presentation.
  phenotype_term:
    preferred_term: Spastic ataxia
    term:
      id: HP:0002497
      label: Spastic ataxia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The phenotypic spectrum of SPG7-related neurologic disorder includes
      uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar
      ataxia, and isolated optic nerve atrophy.
    explanation: Spastic ataxia is the leading presentation of the SPG7 spectrum.
- name: Lower limb spasticity
  category: Neurologic
  description: >-
    Insidiously progressive bilateral leg weakness and spasticity from
    corticospinal tract degeneration.
  phenotype_term:
    preferred_term: Lower limb spasticity
    term:
      id: HP:0002061
      label: Lower limb spasticity
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Initially the spastic paraplegia is typically characterized by insidiously
      progressive bilateral leg weakness and spasticity
    explanation: The corticospinal component of the SPG7 phenotype.
- name: Ataxia
  category: Neurologic
  description: >-
    Cerebellar ataxia with dysarthria and dysphagia, which may be the presenting
    feature rather than the spasticity.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      bilateral leg weakness and spasticity or cerebellar findings (ataxia,
      dysarthria, and dysphagia) or both
    explanation: >-
      Cerebellar findings are an alternative or additional presenting
      manifestation.
- name: Optic atrophy
  category: Ophthalmologic
  description: >-
    Optic neuropathy with decreased visual acuity; isolated optic nerve atrophy is
    itself a recognized presentation of biallelic SPG7 variants.
  phenotype_term:
    preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other central nervous system findings include decreased visual acuity due
      to optic neuropathy, cognitive impairment, and dystonia.
    explanation: Optic neuropathy is an established central feature of SPG7.
- name: Dysarthria
  category: Neurologic
  description: Cerebellar dysarthria accompanying the ataxia.
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar findings (ataxia, dysarthria, and dysphagia)
    explanation: Dysarthria is part of the cerebellar component of SPG7.
- name: Dysphagia
  category: Gastrointestinal
  description: Swallowing difficulty as part of the cerebellar and bulbar involvement.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar findings (ataxia, dysarthria, and dysphagia)
    explanation: Dysphagia is part of the cerebellar component of SPG7.
- name: Cognitive impairment
  category: Neurologic
  description: Cognitive impairment as an additional central nervous system feature.
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other central nervous system findings include decreased visual acuity due
      to optic neuropathy, cognitive impairment, and dystonia.
    explanation: Cognitive impairment is an established central feature of SPG7.
- name: Dystonia
  category: Neurologic
  description: Dystonia as an additional central nervous system feature.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      optic neuropathy, cognitive impairment, and dystonia
    explanation: Dystonia is an established central feature of SPG7.
- name: Peripheral neuropathy
  category: Neurologic
  description: >-
    Motor and sensory neuropathy with neuropathic pain and amyotrophy, the
    peripheral arm of the disorder.
  phenotype_term:
    preferred_term: Peripheral neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Peripheral nervous system involvement manifests as motor and sensory
      neuropathy, neuropathic pain, and amyotrophy.
    explanation: >-
      Establishes the peripheral arm, which is curated separately from the
      central corticospinal arm because the two belong to different mechanism
      modules.
- name: Pes cavus
  category: Musculoskeletal
  description: Pes cavus, part of the associated musculoskeletal involvement.
  phenotype_term:
    preferred_term: Pes cavus
    term:
      id: HP:0001761
      label: Pes cavus
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Associated musculoskeletal involvement includes pes cavus and scoliosis.
    explanation: Pes cavus is an associated musculoskeletal feature of SPG7.
- name: Scoliosis
  category: Musculoskeletal
  description: Scoliosis, part of the associated musculoskeletal involvement.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Associated musculoskeletal involvement includes pes cavus and scoliosis.
    explanation: Scoliosis is an associated musculoskeletal feature of SPG7.
- name: Loss of ambulation
  category: Neurologic
  description: >-
    Progressive spasticity and ataxia may result in wheelchair dependence.
  phenotype_term:
    preferred_term: Loss of ambulation
    term:
      id: HP:0002505
      label: Loss of ambulation
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Spasticity and ataxia are progressive and may result in wheelchair
      dependence.
    explanation: >-
      The source says "may result", so no frequency band is asserted for this
      phenotype.
- name: Amyotrophy
  category: Neurologic
  description: >-
    Muscle wasting accompanying the peripheral nerve involvement. Reported to
    increase substantially between first and follow-up examination in longitudinal
    cohorts, so an entry modelling only the neuropathy understates it.
  phenotype_term:
    preferred_term: Amyotrophy
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Peripheral nervous system involvement manifests as motor and sensory
      neuropathy, neuropathic pain, and amyotrophy.
    explanation: >-
      Amyotrophy is named explicitly in the GeneReviews peripheral-involvement
      sentence already cited in this entry. The preferred_term keeps the clinical
      word "amyotrophy" that the source uses, since the HPO label is the broader
      "Skeletal muscle atrophy".
- name: Neuropathic pain
  category: Neurologic
  description: >-
    Neuropathic pain arising from the peripheral nerve involvement.
  phenotype_term:
    preferred_term: Neuropathic pain
    term:
      id: HP:0012531
      label: Pain
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Peripheral nervous system involvement manifests as motor and sensory
      neuropathy, neuropathic pain, and amyotrophy.
    explanation: >-
      Neuropathic pain is named in the same GeneReviews sentence, which this entry
      previously mined only for the neuropathy itself. Bound to the broader
      HP:0012531 Pain: the specific term HP:6000040 Neuropathic pain exists but
      is not a member of the PhenotypeTerm dynamic enum, so the preferred_term
      carries the specificity the ontology binding cannot.
genetic:
- name: SPG7 pathogenic variants
  gene_term:
    preferred_term: SPG7
    term:
      id: hgnc:11237
      label: SPG7
  association: Causative
  relationship_type: CAUSATIVE
  notes: >-
    Biallelic SPG7 variants encoding paraplegin. The original report identified a
    homozygous 9.5 kb deletion in a 16q24.3-linked family plus two further
    frameshift mutations, one in a complicated and one in a pure form of HSP -
    the phenotypic breadth of this gene was evident from the first description.
    Monoallelic SPG7 variants have been reported in affected individuals but a
    dominant mode remains controversial.
  evidence:
  - reference: PMID:9635427
    reference_title: "Spastic paraplegia and OXPHOS impairment caused by mutations in paraplegin, a nuclear-encoded mitochondrial metalloprotease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Two additional Paraplegin mutations, both resulting in a frameshift, were
      found in a complicated and in a pure form of HSP.
    explanation: >-
      Documents both the loss-of-function mechanism and the pure/complicated
      phenotypic breadth present from the gene's first description.
diagnosis:
- name: Molecular genetic testing for SPG7
  description: >-
    The diagnosis is confirmed by identifying biallelic pathogenic SPG7
    variants in a proband with suggestive findings. Because the phenotypic
    spectrum spans spastic ataxia, pure spinocerebellar ataxia and isolated
    optic atrophy, the suggestive findings that prompt testing are broader
    than a spastic paraparesis alone.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of SPG7-related neurologic disorder is established in a
      proband with suggestive findings and biallelic pathogenic variants in SPG7
      identified by molecular genetic testing.
    explanation: >-
      The GeneReviews confirmatory-testing criterion. Note it says "suggestive
      findings" rather than naming a syndrome, consistent with the breadth of the
      SPG7 phenotypic spectrum this entry curates.
treatments:
- name: Multidisciplinary Supportive Care
  description: >-
    There is no disease-modifying therapy. Management is multidisciplinary care by
    specialists in neurology, ophthalmology, low vision services, audiology,
    urology, physiatry, occupational therapy, physical therapy, orthopedics,
    feeding therapy and nutrition, speech-language therapy, social work,
    psychology, and clinical genetics, with routinely scheduled surveillance for
    emerging manifestations.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Treatment of manifestations: Multidisciplinary care by specialists in
      neurology, ophthalmology, low vision services, audiology, urology,
      physiatry, occupational therapy, physical therapy, orthopedics, feeding
      therapy and nutrition, speech-language therapy, social work, psychology,
      and clinical genetics.
    explanation: >-
      The published management recommendation, curated as supportive because no
      disease-modifying option is offered.
  - reference: PMID:20301286
    reference_title: SPG7-Related Neurologic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Surveillance: Monitor existing manifestations, the individual's response to
      supportive care, and the emergence of new manifestations with routinely
      scheduled evaluations by treating specialists.
    explanation: >-
      Backs the surveillance clause in this treatment's description, which was
      previously a paraphrase with no evidence item behind it.
references:
- reference: PMID:20301286
  title: SPG7-Related Neurologic Disorder.
  tags:
  - GeneReviews
notes: >-
  SPG7 is a mitochondrial disease as much as a spastic paraplegia, and the MONDO
  hierarchy reflects that by placing it under mitochondrial oxidative
  phosphorylation disorder, hereditary spastic paraplegia, and hereditary ataxia
  simultaneously. Curating it only as an HSP understates the phenotype: isolated
  optic atrophy and pure spinocerebellar ataxia are both recognized presentations
  of the same biallelic genotype, so SPG7 belongs in the differential for
  adult-onset ataxia and for optic neuropathy, not only for spastic paraparesis.


  The subcellular sequence - mitochondrial transport failure, then degeneration
  beginning at the synaptic terminal - rests on the Drosophila SPG7 null and is
  curated as MODEL_ORGANISM evidence. The human evidence establishes the OXPHOS
  lesion (in patient muscle) and the corticospinal degeneration (clinically), but
  not the order in which the axonal compartment fails.


  The monoallelic question is deliberately left open. Several studies report a
  single heterozygous SPG7 variant in affected individuals, but GeneReviews
  explicitly calls dominant inheritance controversial, so this entry curates only
  the recessive mode and records the dispute as PARTIAL evidence on the
  inheritance block rather than adding a dominant one.

📚

References & Deep Research

References

1

PMID:20301286

SPG7-Related Neurologic Disorder.

No top-level findings curated for this source.

Deep Research

1

Claude Code ▸

Hereditary Spastic Paraplegia 7 (SPG7) — Comprehensive Disease Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 34 citations 2026-08-24T18:55:49.507129

Hereditary Spastic Paraplegia 7 (SPG7) — Comprehensive Disease Research Report

1. Disease Information

Overview. Hereditary Spastic Paraplegia 7 (SPG7; also called SPG7-related neurologic disorder) is an autosomal recessive neurodegenerative disorder caused by biallelic pathogenic variants in SPG7, which encodes the mitochondrial inner-membrane m-AAA protease subunit paraplegin. It is the first-identified autosomal recessive form of hereditary spastic paraplegia (HSP) and one of the most common causes of autosomal recessive HSP and spastic ataxia, accounting for roughly 5–12% of AR-HSP cases. The classic presentation is slowly progressive bilateral lower-limb spasticity and weakness from corticospinal tract axonal degeneration, but SPG7 is now recognized as a broad phenotypic spectrum encompassing uncomplicated spastic paraplegia, complicated spastic ataxia, isolated cerebellar/spinocerebellar ataxia, isolated optic atrophy, chronic progressive external ophthalmoplegia (PEO), and other presentations (GeneReviews, NCBI Bookshelf NBK1107).

Key identifiers: - OMIM: #607259 (Spastic Paraplegia 7, Autosomal Recessive); gene locus OMIM #602783 (SPG7 Matrix AAA Peptidase Subunit, Paraplegin) (OMIM #607259; OMIM #602783) - Gene location: Chromosome 16q24.3 - GeneReviews: SPG7-Related Neurologic Disorder (NBK1107) - GARD/NIH Rare Disease listing: Hereditary spastic paraplegia 7 - GTR condition record: C1846564 - Reference transcript: NM_003119 (used for HGVS variant nomenclature in ClinVar)

Synonyms/alternative names: Spastic paraplegia 7, autosomal recessive; SPG7-related disorder; hereditary spastic ataxia-7; paraplegin deficiency; SPG7 spastic ataxia; autosomal recessive spastic ataxia with optic atrophy (in some phenotype descriptions).

Evidence base. Information derives primarily from aggregated cohort/disease-level resources (GeneReviews expert-curated summaries drawing on the international cohort of Coarelli et al. 2019 [n=241], OMIM, and case series/registries), not raw individual-level EHR data. Molecular/mechanistic data derive from model-organism (mouse, Drosophila) and patient-derived iPSC/fibroblast studies.

2. Etiology

Disease Causal Factors

SPG7 is a monogenic mitochondrial disorder. Biallelic (homozygous or compound heterozygous) loss-of-function or missense pathogenic variants in SPG7 impair the m-AAA protease, causing progressive degeneration of the longest corticospinal and cerebellar axons — a length-dependent "dying-back" axonopathy driven by mitochondrial dysfunction and impaired axonal transport (see Mechanism, §6).

Risk Factors

Genetic risk factors:
Causal biallelic variants in SPG7 (>100 reported pathogenic variants: missense, nonsense, frameshift, splice-site, and rare deletion/duplication CNVs).
p.Ala510Val (c.1529C>T) is the single most prevalent pathogenic allele, with a reported carrier frequency up to ~1% in the general population — making it a common "hypomorphic" variant that frequently appears in trans with a second, more severe allele, and occasionally appears to act as a low-penetrance dominant risk allele.
p.Leu78Ter (c.233T>A), a nonsense variant in exon 2, was the most frequent variant in a Hungarian cohort (Frontiers Genetics, PMC12215234), with gnomAD minor allele frequency 0.0028 in South Asians (5 homozygotes reported).
Compound heterozygosity/consanguinity in populations with elevated consanguinity rates increases homozygosity risk.
Heterozygous monoallelic SPG7 variants have been reported as possible risk/modifier alleles for amyotrophic lateral sclerosis (ALS), and digenic heterozygosity with AFG3L2 (the paralogous m-AAA subunit) causes a distinct motor-neuron/cerebellar disorder (see below).
Environmental/demographic risk factors: None specifically established; disease is fully genetically determined, though age (onset window 20–40, mean 35.5 ± 14.3 years; range infancy to age 72) modifies symptom expression.
Protective factors: None specifically documented in the literature reviewed; no known protective genetic modifiers or lifestyle protective factors are established.
Gene-environment interactions: Not established for SPG7; disease penetrance and severity appear driven by variant type (loss-of-function vs. missense) rather than documented environmental modifiers.

3. Phenotypes

Frequencies below are drawn from the international GeneReviews-cited cohort (Coarelli et al. 2019, n=241), reported at first and follow-up ("second") examination, reflecting disease progression over time:

Phenotype	HPO term (suggested)	Frequency (1st exam → 2nd exam)	Onset/course
Lower-limb spasticity / pyramidal syndrome	HP:0001257 (Spasticity) / HP:0002061 (Spastic paraplegia)	89% → 97%	Progressive; severe gait abnormality in ~1/3 of individuals 8–10 yrs post-onset
Hyperreflexia	HP:0001347	Common, part of pyramidal syndrome	Progressive
Extensor plantar (Babinski) response	HP:0003487	Common	Progressive
Cerebellar ataxia (gait/limb)	HP:0001251	66% → 78%	Progressive
Cerebellar dysarthria	HP:0001260	42% → 57%	Progressive
Dysphagia	HP:0002015	15% → 28%	Progressive
Muscle wasting/amyotrophy	HP:0003202	10% → 30%	Progressive; distal predominance
Cognitive impairment (executive/visuoconstructive)	HP:0100543	8% → 19%	Progressive, mild
Decreased visual acuity (optic neuropathy)	HP:0000572 / HP:0000648 (Optic atrophy)	7% → 14%	Progressive
Ptosis	HP:0000508	5% → 17%	Progressive
Dystonia (mainly lower limb)	HP:0001332	2% → 11.5%	Progressive
Ophthalmoparesis/progressive external ophthalmoplegia	HP:0000602	Variable (in one cohort, PEO seen in 1 patient)	Variable
Nystagmus	HP:0000639	Common ocular finding (65% ocular abnormality overall; nystagmus most frequent)	Variable
Peripheral sensorimotor neuropathy	HP:0007141	Present in subset	Progressive
Neuropathic pain	HP:0012532	Present in subset	Variable
Pes cavus	HP:0001762	Reported	Static/progressive
Scoliosis	HP:0002650	Reported	Progressive
Hearing loss	HP:0000365	Reported in subset	Variable
Urinary urgency/bladder dysfunction	HP:0000012	Common, part of complicated HSP	Progressive
Loss of vibratory sense	HP:0007190	Common	Progressive

Phenotype spectrum categories (GeneReviews): uncomplicated spastic ataxia, complicated spastic ataxia, spinocerebellar ataxia, and isolated optic nerve atrophy — the boundaries between these presentations are not fixed, and spasticity and ataxia can occur "in isolation, at the same time, or sequentially," with most patients eventually developing both.

Age of onset: Mean 35.5 ± 14.3 years (typically 20–40 years), but ranges from infancy to age 72.

Progression: Insidious, slowly progressive. Roughly one-third of individuals show severe gait abnormality within 8–10 years of onset; some become wheelchair-dependent.

Quality of life impact: A cerebello-cortical connectivity study found cognitive and social/behavioral deficits (e.g., disturbed attention, executive function, emotional communication impairment) linked to cerebellar-cortical circuit alterations in SPG7 patients (PMC7053515). Progressive mobility loss, dysphagia risk (aspiration), visual impairment, and bladder dysfunction compound cumulative disability and reduced independence over the disease course.

4. Genetic/Molecular Information

Causal gene: SPG7 (HGNC gene symbol SPG7; protein: paraplegin), chromosome 16q24.3, OMIM gene entry #602783.

Variant classification and types: - >100 reported pathogenic/likely pathogenic variants (ClinVar, HGMD): missense, nonsense, frameshift, splice-site, and rare deletion/duplication CNVs. - Detection rates: sequence analysis (missense/nonsense/small indel/splice) detects >90% of pathogenic alleles; gene-targeted deletion/duplication analysis (qPCR, long-range PCR, MLPA, targeted microarray) detects <10% of the remainder. - Deep intronic/non-coding variants missed by exome sequencing have been identified via genome sequencing, explaining some cases with only one variant found by exome (PMC12883507 — "Identification of an additional deep intronic splice variant prompts critical evaluation of SPG7 inheritance").

Recurrent/founder variants: - p.Ala510Val (c.1529C>T) — most common pathogenic allele overall; population carrier frequency up to ~1%; associated with a cerebellar-ataxia-predominant phenotype and slightly later onset; frequently found as compound heterozygote or in apparent pseudodominant pedigrees. - p.Leu78Ter (c.233T>A) — nonsense/loss-of-function variant, most common in a Hungarian cohort; associated with more severe, spasticity/pyramidal-and-optic-atrophy–predominant phenotype (loss-of-function genotype-phenotype correlation).

Genotype-phenotype correlation: Biallelic loss-of-function variants correlate with more pronounced pyramidal signs and optic atrophy; individuals carrying at least one missense allele (especially p.Ala510Val) tend to show more pronounced ataxia relative to spasticity.

Population/allele frequency databases: gnomAD, 1000 Genomes, ExAC/TOPMed for carrier-frequency and homozygote counts (e.g., p.Leu78Ter MAF 0.002778 in South Asian gnomAD subpopulation, 5 homozygotes).

Functional consequences: Loss of paraplegin function impairs the mitochondrial m-AAA protease quality-control complex (formed with AFG3L2), causing reduced Complex I respiratory chain activity, defective processing of mitochondrial substrates (e.g., MRPL32, EMRE), and dysregulated mitochondrial calcium handling via altered MCU-EMRE assembly and the mitochondrial permeability transition pore (mPTP) (Cell Research review, PMC5835776).

Modifier genes / digenic interaction: AFG3L2 — the paralogous m-AAA protease subunit (mutated in autosomal dominant SCA28) — physically and functionally interacts with paraplegin. A 2025 study (medRxiv/BMC Medicine) found digenic combined heterozygosity in SPG7 + AFG3L2 in patients with motor neuron disease and cerebellar ataxia phenotypes: among 4,817 MND/ataxia patients, 6 carried digenic variants (none among 1,827 controls); segregation in families was perfect; animal models with combined dysfunction of both genes show early-onset axonal degeneration and prominent Purkinje cell loss (BMC Medicine 2025; medRxiv preprint).

Epigenetic information: No disease-specific epigenetic (DNA methylation/histone) mechanism has been established for SPG7 in the literature reviewed.

Chromosomal abnormalities: SPG7 is caused by point mutations/small indels, not large chromosomal rearrangements; no recurrent CNV/aneuploidy syndrome association identified.

Mitochondrial genome consequence (secondary): Pathogenic SPG7 variants cause secondary mitochondrial DNA instability — multiple mtDNA deletions accumulate in postmitotic tissue (skeletal muscle), analogous to POLG-related disorders, due to disordered mtDNA maintenance (Brain 2014, Hudson lab study). Single-fiber molecular studies show multiple mtDNA deletions segregating at 38–97% heteroplasmy in COX-deficient muscle fibers (PMC3899233).

5. Environmental Information

No established environmental, lifestyle, or infectious causal or exacerbating factors are documented for SPG7 in the literature surveyed — it is a fully genetically determined mitochondrial disorder. No infectious agents are implicated. Systemic mitochondrial-toxic environmental exposures have not been specifically studied as modifiers of SPG7 severity, though caution around known mitochondrial-toxic drugs (e.g., certain antiretrovirals, statins in some mitochondrial disease contexts) may be prudent extrapolation from general mitochondrial disease management principles, not SPG7-specific evidence.

6. Mechanism / Pathophysiology

Molecular function of paraplegin. Paraplegin is the catalytic ATP-dependent metalloprotease subunit of the mitochondrial inner-membrane m-AAA protease complex, forming a hetero-oligomer with AFG3L2. This complex: 1. Performs mitochondrial protein quality control — degrading misfolded polypeptides and unassembled proteins on the matrix side of the inner mitochondrial membrane. 2. Carries out proteolytic maturation of specific substrates, including ribosomal protein MRPL32 (required for mitochondrial ribosome assembly/translation) and EMRE (a component of the mitochondrial calcium uniporter, MCU). 3. Regulates mitochondrial calcium homeostasis, limiting MCU-EMRE complex assembly and thereby modulating opening of the mitochondrial permeability transition pore (mPTP) — a key determinant of cell death susceptibility (Cell Research, PMC5835776).

Causal chain (trigger → consequence): 1. Biallelic SPG7 loss-of-function/missense variant → loss of functional m-AAA protease (paraplegin-AFG3L2 complex). 2. → Reduced mitochondrial Complex I respiratory chain activity and impaired mitoribosomal protein maturation (MRPL32 processing failure). 3. → Mitochondrial calcium dysregulation (via defective EMRE processing / MCU-EMRE control) and increased mPTP susceptibility. 4. → Secondary mitochondrial genome instability — accumulation of multiple mtDNA deletions in postmitotic tissues (muscle, neurons), producing COX-deficient, ragged-red fibers. 5. → Mitochondrial morphological abnormalities — swollen, dysmorphic mitochondria appearing first in distal axons and synaptic terminals, well before axonal swelling (mouse model: swollen mitochondria at 4.5 months, axonal swelling at 8 months, degeneration at 15 months — JCI, Ferreirinha et al. 2004). 6. → Impaired axonal transport — anterograde transport impairment causes massive accumulation of organelles and neurofilaments within axonal swellings; retrograde transport is also delayed in symptomatic animals. 7. → Length-dependent ("dying-back") axonal degeneration — preferentially affecting the longest and largest-caliber axons: the corticospinal tract (causing spasticity), cerebellar afferent/efferent pathways (ataxia), and optic nerve (optic atrophy), because these neurons are most dependent on efficient long-distance axonal mitochondrial transport and energy supply. 8. → Clinical manifestation: progressive spastic paraparesis, cerebellar ataxia/dysarthria/dysphagia, optic atrophy, peripheral neuropathy, and (in a subset) PEO from muscle mtDNA deletion accumulation.

Cell types/tissues involved: upper motor neurons of corticospinal tract (Betz cells, axons), Purkinje cells and cerebellar circuitry, retinal ganglion cells/optic nerve axons, peripheral sensory/motor neurons, skeletal muscle fibers (secondary mitochondrial myopathy), and in digenic SPG7/AFG3L2 models, astrocytes (astrocyte-specific m-AAA protease deletion reveals a glial contribution to neurodegeneration — PMC6618114).

Suggested ontology terms: - GO biological process: GO:0034982 (mitochondrial protein processing), GO:0006515 (protein quality control for misfolded/incompletely synthesized proteins), GO:0051560 (mitochondrial calcium ion homeostasis), GO:0007005 (mitochondrion organization), GO:0008090 (retrograde axonal transport), GO:0008089 (anterograde axonal transport) - GO molecular function: GO:0004176 (ATP-dependent peptidase activity), GO:0004222 (metalloendopeptidase activity) - GO cellular component: GO:0005743 (mitochondrial inner membrane), GO:0031966 (mitochondrial membrane) - CL cell types: CL:0000029 (neuron, Betz cell / upper motor neuron equivalent), CL:0000121 (Purkinje cell), CL:0000740 (retinal ganglion cell), CL:0000187 (myocyte, skeletal muscle) - CHEBI: CHEBI:29108 (calcium(2+) ion) for the calcium-dysregulation arm

Molecular profiling / omics findings: Patient-derived iPSC neurons and fibroblasts show mitochondrial functional deficits specific to SPG7 (contrasted with SPAST-mutant HSP lines, which do not show comparable mitochondrial deficits) (PMC7469654). A 2023 high-throughput pharmacological rescue study in SPG7 patient-derived neurons identified compounds that reverse mitochondrial and neuronal phenotypic defects, supporting mitochondrial dysfunction as a druggable node (Frontiers in Neuroscience, PMC10520970).

7. Anatomical Structures Affected

Organ/system level: - Primary: Central nervous system — corticospinal tracts (spinal cord lateral columns), cerebellum (cortex, dentate nuclei, peduncles), optic nerve. - Secondary: Peripheral nervous system (sensorimotor peripheral nerves), skeletal muscle (secondary mitochondrial myopathy with COX-deficient/ragged-red fibers), extraocular muscles (in PEO variant), bladder (neurogenic dysfunction), skeletal system (secondary orthopedic deformity — pes cavus, scoliosis from chronic spasticity/imbalance), auditory system (sensorineural hearing loss in a subset). - Body systems: nervous system (primary), musculoskeletal, ophthalmologic, urologic.

Tissue/cell level: Corticospinal upper motor neuron axons (longest CNS axons, most vulnerable); cerebellar Purkinje cells and associated circuitry; retinal ganglion cell axons forming the optic nerve; peripheral motor/sensory axons; skeletal and extraocular muscle fibers.

Subcellular level: Mitochondria — specifically the inner mitochondrial membrane (where the m-AAA protease complex resides), affecting mitochondrial matrix protein quality control and mitochondrial DNA maintenance/nucleoid stability.

UBERON terms (suggested): UBERON:0002240 (spinal cord), UBERON:0002037 (cerebellum), UBERON:0001784 (lateral corticospinal tract) / UBERON:0002367 (corticospinal tract), UBERON:0000941 (optic nerve), UBERON:0001017 (central nervous system), UBERON:0000010 (peripheral nervous system), UBERON:0001134 (skeletal muscle tissue).

GO Cellular Component: GO:0005743 (mitochondrial inner membrane), GO:0005759 (mitochondrial matrix).

Localization/laterality: Bilateral and symmetric involvement of corticospinal tracts and cerebellar structures is characteristic (distinguishing from focal/asymmetric lesions); cerebellar atrophy in SPG7 has been reported to preferentially involve the cerebellar hemispheres rather than the vermis in at least one imaging series, and the "hot cross bun" pontine sign classically associated with MSA-C is not a typical SPG7 finding (Human Genome Variation, PMC4785587).

8. Temporal Development

Onset: Adult-onset in the majority (mean 35.5 ± 14.3 years; typical range 20–40 years), but documented range extends from infancy to age 72 — making SPG7 a disorder with wide age-of-onset variability even within families (intrafamilial range 7–35 years documented).
Onset pattern: Insidious/gradual, not acute or episodic.
Progression: Slowly progressive, typically over years to decades. Pyramidal signs are usually earliest/most prevalent (89% at first exam, rising to 97%), with cerebellar features (66%→78%), dysarthria (42%→57%), dysphagia (15%→28%), amyotrophy (10%→30%), cognitive impairment (8%→19%), visual loss (7%→14%), ptosis (5%→17%), and dystonia (2%→11.5%) all increasing in frequency at longitudinal follow-up — demonstrating a cumulative, multisystem progressive course rather than a stable or episodic one.
Disease course pattern: Chronic, progressive, lifelong; not relapsing-remitting.
Severity milestone: Roughly one-third of affected individuals develop severe gait abnormality (wheelchair dependence in some) within 8–10 years of symptom onset.
Remission patterns: None documented — SPG7 does not remit spontaneously; no disease-modifying treatment currently alters the progressive course.
Critical periods: No defined developmental critical window; the length-dependent axonopathy mechanism implies risk accumulates with axon length and metabolic demand over time rather than at a discrete developmental stage, consistent with the typically adult (rather than pediatric) symptom onset despite the causal mutation being congenital.

9. Inheritance and Population

Epidemiology: - Global prevalence of all HSP forms: ~3.6 per 100,000. - Global prevalence of SPG7 specifically: ~0.22 per 100,000 (modeled estimate; BMC Neurology 2022; PMC8944001). - SPG7 accounts for 5–12% of autosomal recessive HSP cases and is recognized as a common cause of previously undiagnosed adult-onset ataxia ("SPG7 mutations are a common cause of undiagnosed ataxia," Neurology 2015).

Inheritance pattern: Autosomal recessive (biallelic pathogenic variants required in the classic model). However: - Multiple reports of apparent autosomal dominant inheritance with a single heterozygous variant have emerged, and "the possibility of autosomal dominant inheritance remains controversial" per GeneReviews. - Much of this apparent dominance is now attributed to (1) pseudodominance — an autosomal recessive disorder appearing across two generations because the founder allele (e.g., p.Ala510Val, carrier frequency ~1%) is common enough that an affected homozygote's partner is frequently also a carrier, producing affected offspring without consanguinity; and (2) "missing heritability" — a second pathogenic allele in a deep intronic or other non-coding region that is missed by exome sequencing but detectable by genome sequencing (PMC12883507; "Evidence for non-Mendelian inheritance in spastic paraplegia 7," medRxiv). - Digenic inheritance with AFG3L2 is a separate, recently described mechanism producing a related but distinct motor-neuron/cerebellar phenotype through combined heterozygosity across the two m-AAA protease genes.

Penetrance/expressivity: Full biallelic genotypes are generally considered highly, though not completely, penetrant; monoallelic (heterozygous) carriers are typically unaffected clinically but may show subtle imaging changes (reduced white matter integrity in the corpus callosum on DTI in heterozygote carriers). Expressivity is markedly variable — intrafamilial variation in age of onset (7–35 years) and in phenotype (pure spastic paraplegia through complicated spastic ataxia) is well documented even among relatives sharing the same genotype.

Genetic anticipation: Not established/reported for SPG7 (unlike triplet-repeat spinocerebellar ataxias).

Germline mosaicism: Not specifically documented in the literature reviewed for SPG7.

Founder effects / carrier frequency: p.Ala510Val is a recurrent, likely founder-associated allele with carrier frequency up to ~1% in general populations; p.Leu78Ter shows elevated frequency in South Asian gnomAD subpopulation (MAF 0.0028) and was most frequent in a Hungarian cohort — suggesting population-specific variant spectra.

Consanguinity: As an autosomal recessive disorder, parental consanguinity is a recognized risk factor and diagnostic clue (elicited in the family history per GeneReviews suggestive-findings criteria).

Population demographics: No strong ethnic-specific prevalence differences beyond the founder-allele distribution noted above; affects males and females roughly equally (no established sex-ratio skew, consistent with autosomal — not X-linked — inheritance). Age distribution reflects the adult-onset pattern described above.

10. Diagnostics

Clinical suggestive findings (GeneReviews): adult-onset (mean 35.5 years) uncomplicated or complicated spastic paraplegia, cerebellar ataxia, and/or optic nerve atrophy on exam; brain MRI with cerebellar atrophy or corticospinal/frontal white-matter changes on DTI; family history compatible with autosomal recessive inheritance (affected siblings, consanguinity).

Establishing the diagnosis: Biallelic pathogenic SPG7 variants identified by molecular genetic testing in a proband with suggestive findings.

Molecular genetic testing: - Multigene panel (SPG7 + other HSP genes) — first-line, focused. - Exome sequencing — detects >90% of pathogenic variants (option when panel is uninformative or phenotype is broad). - Genome sequencing — recommended when only one pathogenic allele is found by exome, to detect deep intronic/non-coding variants. - Deletion/duplication analysis (qPCR, long-range PCR, MLPA, targeted array) — needed for the <10% of alleles that are CNVs.

Imaging: - Brain MRI: cerebellar atrophy (reported as preferentially hemispheric rather than vermian in some series) and/or cortical atrophy; diffusion tensor imaging shows white matter changes in frontal lobes, corticospinal tracts, and brainstem. - The "hot cross bun" pontine sign (classic for MSA-C) is not a typical SPG7 finding, aiding radiological differentiation.

Laboratory/histopathology: - Skeletal muscle biopsy in severely affected individuals: ragged-red fibers and cytochrome c oxidase (COX)-deficient fibers, reflecting secondary mitochondrial dysfunction and multiple mtDNA deletions (up to 38–97% heteroplasmy in individual respiratory-deficient fibers). - Optical coherence tomography (OCT): useful for detecting subclinical optic neuropathy.

Differential diagnosis: Other AR/AD-HSP subtypes; spinocerebellar ataxias (SCA1, 2, 3, 6, 7, 17; DRPLA); AFG3L2-related autosomal recessive SCA (shares the same pathway); other mitochondrial disorders with overlapping ptosis/ophthalmoplegia/optic atrophy (e.g., POLG-related disease, which also causes multiple mtDNA deletions); treatable mimics such as dopa-responsive dystonia and specific metabolic disorders should be excluded given management implications.

Screening: No population newborn-screening program exists (adult-onset disorder); carrier/cascade testing and prenatal/preimplantation genetic testing are available once family-specific variants are identified.

Suggested NCIT terms: NCIT:C15709 (Genetic Testing) generally; specific molecular diagnostic procedures map to NCIT terms for exome sequencing, genome sequencing, and muscle biopsy as applicable.

11. Outcome/Prognosis

Survival/mortality: SPG7 is generally not associated with reduced life expectancy from the core neurodegenerative process itself; disability rather than mortality is the primary burden. No specific survival/mortality statistics were located in the sources reviewed (consistent with a slowly progressive, non-lethal neurodegenerative disorder in most cases, though secondary complications of severe disability — e.g., aspiration from dysphagia — could contribute to morbidity/mortality risk in advanced disease).
Morbidity/functional outcomes: Progressive gait impairment, with severe gait abnormality in ~1/3 of patients by 8–10 years post-onset; a subset become wheelchair-dependent. Multisystem morbidity accumulates over the disease course (see §3/§8 frequency table): dysarthria, dysphagia (aspiration risk), amyotrophy, cognitive impairment, visual loss, ptosis, and dystonia.
Complications: Aspiration pneumonia risk from dysphagia; bladder dysfunction complications (UTIs); orthopedic complications (contractures, scoliosis, pes cavus) from chronic spasticity/gait abnormality; social/cognitive impact from cerebello-cortical circuit dysfunction affecting attention, executive function, and social cognition.
Prognostic factors: Genotype correlates with phenotype trajectory — biallelic loss-of-function variants predict a more pyramidal/optic-atrophy-predominant, potentially more severe course; missense variants (notably p.Ala510Val) correlate with a more cerebellar-ataxia-predominant course with somewhat later onset.
Quality of life measurement: No SPG7-specific validated QoL instrument identified; standardized ataxia severity scales (SARA, ICARS, BARS) are used for longitudinal tracking rather than generic QoL tools in the surveillance framework.

12. Treatment

No disease-modifying cure or specific drug therapy exists. Management is entirely supportive and multidisciplinary, involving neurology, ophthalmology, occupational/physical therapy, physiatry, orthopedics, nutrition, speech-language pathology, urology, social work, psychology, and clinical genetics.

Pharmacotherapy for spasticity (symptomatic, not disease-modifying): - Oral antispasticity agents: baclofen, tizanidine, dantrolene, diazepam (NCIT:C529 Baclofen, general pharmacotherapy class NCIT:C15986). - Botulinum toxin injections for focal spasticity. - Intrathecal baclofen pump for severe, refractory spasticity.

Rehabilitative/supportive care: - Physical therapy: balance exercises, gait training, muscle strengthening (NCIT:C15302, Physical Therapy). - Occupational therapy: adaptive devices (weighted utensils, dressing aids) (NCIT:C15302-adjacent). - Mobility aids: canes, walkers, motorized wheelchairs; home modifications (grab bars, ramps). - Speech-language therapy for dysarthria; augmentative/alternative communication evaluation. - Dysphagia management: feeding therapy, video esophagram-guided diet modification, gastrostomy tube for high aspiration risk. - Vision: corrective lenses, prisms, low-vision services for optic atrophy. - Bladder management: antimuscarinics, beta-3 agonists, botulinum toxin per urology. - Orthopedic: orthotic devices for pes cavus/scoliosis. - Cognitive/psychiatric: standard pharmacotherapy and psychotherapy/neuropsychological rehabilitation as needed.

Experimental/investigational approaches: - Pharmacological rescue studies in patient-derived iPSC neurons (high-throughput screening) have identified small molecules that reverse SPG7-associated mitochondrial and neuronal phenotypic defects in vitro — an early-stage discovery platform, not yet a clinical therapy (Frontiers Neuroscience 2023, PMC10520970). - Digital-motor outcome measures are being developed specifically as candidate endpoints for future SPG7 clinical trials, reflecting active trial-readiness research even though no SPG7-specific disease-modifying trial was identified as completed/ongoing ("Patient-Relevant Digital-Motor Outcomes for Clinical Trials in Hereditary Spastic Paraplegia Type 7," Neurology 2024). - Coenzyme Q10/mitochondrial cofactor supplementation strategies have been trialed in other mitochondrial diseases (e.g., NCT00432744, Phase III CoQ10 in mitochondrial disease; NCT01126697, CoQ10 + lisinopril in muscular dystrophies) but no SPG7-specific CoQ10/idebenone trial was located in this search — this represents a plausible but currently unvalidated extrapolated intervention for the SPG7 mitochondrial mechanism. - No approved gene therapy, cell therapy, or targeted molecular therapy currently exists for SPG7 in humans (an experimental intramuscular viral delivery of paraplegin rescued peripheral axonopathy in the mouse model — a proof-of-concept gene-replacement study, not yet translated to human trials — JCI 2005).

Genotype-informed considerations: No current pharmacogenomic (CPIC/PharmGKB) guidance specific to SPG7 was identified.

13. Prevention

Primary prevention: Not applicable in the traditional sense (no modifiable environmental cause); the relevant primary-prevention lever is genetic: carrier screening and reproductive genetic counseling in families/populations with known pathogenic alleles (notably relevant given the ~1% carrier frequency of p.Ala510Val).
Secondary prevention: Early molecular diagnosis via genetic testing in individuals with suggestive adult-onset spastic ataxia/optic atrophy enables earlier initiation of supportive/rehabilitative care and surveillance, and informs family counseling before further affected pregnancies occur.
Genetic counseling: Sibling recurrence risk 25% (affected) / 50% (carrier) / 25% (unaffected, non-carrier) when both parents are known heterozygotes; offspring of an affected individual are obligate heterozygous carriers (and could be at risk of being affected if the partner also carries a pathogenic allele, given founder-allele carrier frequency). Prenatal and preimplantation genetic testing are available once family-specific variants are identified.
Screening programs: No population-based newborn screening exists for SPG7 (adult-onset, non-emergent phenotype); carrier screening is family/variant-specific rather than population-panel-based at this time, though its relatively high founder-allele carrier frequency could support future consideration in expanded carrier panels.
Behavioral/lifestyle interventions: No specific risk-reducing lifestyle intervention is established; general good mitochondrial-health practices (avoidance of mitochondrial-toxic drugs where possible, regular exercise/physical therapy to maintain function) are reasonable extrapolated supportive measures rather than evidence-based disease-modifying prevention.
Public health/environmental interventions: Not applicable — SPG7 has no environmental or infectious trigger requiring public health intervention.

14. Other Species / Natural Disease

Taxonomy: SPG7 orthologs show stringent 1:1 orthology across vertebrates: human (Homo sapiens, NCBITaxon:9606), mouse (Mus musculus, NCBITaxon:10090), rat (Rattus norvegicus, NCBITaxon:10116), and zebrafish (Danio rerio, NCBITaxon:7955; UniProt E7F2S4).
Gene orthologs: Mouse Spg7 (MGI:2385906); Drosophila paraplegin ortholog (studied via null-mutant/deletion models).
Natural disease in other species: No naturally occurring companion-animal or wildlife SPG7-orthologous disease was identified in this search (OMIA not specifically queried/found with a hit); the available animal data are all engineered/induced models (knockouts), not natural disease.
Comparative biology: The m-AAA protease mechanism (paraplegin-AFG3L2 complex) and its role in mitochondrial protein quality control, calcium homeostasis, and axonal maintenance is evolutionarily conserved from yeast (yeast m-AAA protease orthologs originally characterized the pathway) through Drosophila, zebrafish, mouse, and human — underscoring deep conservation of the disease mechanism.
Zoonotic potential/cross-species transmission: Not applicable — SPG7 is a non-infectious, genetic, non-transmissible disorder.

15. Model Organisms

Model	Type	Key findings	Fidelity/limitations
Paraplegin-deficient mouse (Ferreirinha et al. 2004; JCI)	Genetic knockout (mammalian)	Slow, progressive motor impairment (rotarod deficits); distal axonopathy of spinal and peripheral axons with axonal swelling and degeneration. Temporal sequence: swollen mitochondria in spinal cord axons at 4.5 months → axonal swelling at 8 months → degeneration at 15 months. Swellings show massive accumulation of organelles/neurofilaments (impaired anterograde transport); retrograde transport delayed in symptomatic mice.	RECAPITULATES the length-dependent axonal degeneration and mitochondrial-transport mechanism; a mammalian model with strong construct and face validity for the corticospinal/peripheral axonopathy arm.
Intramuscular AAV-paraplegin gene delivery in paraplegin-null mice (JCI 2005)	Induced/rescue model	Viral delivery of paraplegin rescued peripheral axonopathy — proof-of-concept for gene-replacement therapy.	RESCUES peripheral (not central) axonopathy; demonstrates causal sufficiency of paraplegin restoration.
Drosophila SPG7-null mutant (Cell Death & Disease 2018; PMC5833341)	Genetic knockout (invertebrate)	Mitochondrial dysfunction, shortened lifespan, neuronal and muscular degeneration; reduced respiratory chain complex I and II activity; electron-dense material accumulation in flight-muscle mitochondria; severely swollen/dysmorphic mitochondria in photoreceptor synaptic terminals.	RECAPITULATES core mitochondrial bioenergetic and morphological defects; useful for rapid genetic/pharmacological screening; limited translational fidelity for CNS-specific corticospinal phenotype (invertebrate nervous system).
Zebrafish spg7 ortholog (UniProt E7F2S4)	Genetic (potential knockout/knockdown model)	Confirmed conserved 1:1 ortholog present; disease-specific phenotyping less thoroughly documented in the sources reviewed compared to other HSP genes (e.g., spastizin/SPG15 zebrafish models are more developed).	Model existence confirmed by orthology; disease-modeling literature less extensive than mouse/Drosophila for SPG7 specifically.
Astrocyte-specific m-AAA protease conditional knockout mouse (PMC6618114)	Conditional genetic knockout (glial-specific)	Reveals a glial (astrocyte) contribution to neurodegeneration in m-AAA protease deficiency, expanding the mechanism beyond cell-autonomous neuronal axonopathy.	PARTIALLY_RECAPITULATES — isolates the astrocytic arm; complements but does not replace the neuron-autonomous mouse knockout model.
Combined SPG7 + AFG3L2 dysfunction animal models (cited in digenic-inheritance study, BMC Medicine 2025)	Genetic (double dysfunction)	Early-onset axonal degeneration, prominent cerebellar degeneration with Purkinje cell and parallel fiber loss, reactive astrogliosis, defective mitochondria.	RECAPITULATES the more severe digenic human phenotype (motor neuron + cerebellar disease); supports the synergistic pathogenic model for combined SPG7/AFG3L2 heterozygosity.
Patient-derived iPSC/fibroblast lines (PMC7469654; PMC10520970)	Human cellular model (in vitro, IN_VITRO evidence class)	SPG7 patient-derived neurons/fibroblasts show mitochondrial functional deficits not seen in SPAST-mutant (SPG4) patient lines, establishing SPG7 as mechanistically distinct within HSP; used as a platform for high-throughput pharmacological rescue screening.	HIGH translational relevance (human genetic background) but lacks the in vivo axonal-length/circuit context of animal models — best used in combination with the mouse model.

Research applications: These models collectively support study of (1) the temporal sequence of mitochondrial dysfunction preceding axonal degeneration, (2) axonal transport impairment as a proximate mechanism, (3) cell-autonomous (neuronal) vs. non-cell-autonomous (astrocytic) contributions, (4) digenic/synergistic genetic interactions (SPG7+AFG3L2), and (5) small-molecule/gene-therapy rescue strategies as a translational pipeline toward future SPG7 clinical trials.

Summary of Key Ontology Term Suggestions for KB Curation

Domain	Suggested terms
Disease	MONDO (SPG7-related neurologic disorder; exact MONDO CURIE not confirmed in this search — verify via OAK/MONDO lookup before curating), OMIM:607259
Gene	HGNC symbol SPG7 (paraplegin), OMIM:602783
Phenotypes (HP)	Spastic paraplegia, cerebellar ataxia, dysarthria, dysphagia, muscle wasting/amyotrophy, optic atrophy, ptosis, dystonia, nystagmus, ophthalmoparesis, peripheral neuropathy, pes cavus, scoliosis, hearing loss, urinary urgency, hyperreflexia, Babinski sign
GO Biological Process	mitochondrial protein processing/quality control, mitochondrial calcium ion homeostasis, anterograde/retrograde axonal transport, mitochondrion organization
GO Molecular Function	ATP-dependent peptidase activity, metalloendopeptidase activity
GO Cellular Component	mitochondrial inner membrane, mitochondrial matrix
CL cell types	upper motor neuron/corticospinal neuron, Purkinje cell, retinal ganglion cell, skeletal myocyte, astrocyte
UBERON	spinal cord, cerebellum, corticospinal tract, optic nerve, skeletal muscle tissue
NCIT treatments	Pharmacotherapy (C15986), Physical Therapy (C15302), Genetic Counseling (C15240), Genetic Testing
Model organisms (NCBITaxon)	Mouse (10090), Drosophila (7227, implied), Zebrafish (7955)

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	17
Resolved	4
Unresolved (possible confabulation)	0
Unverifiable	13
References weighed for topical relevance	4
On topic	2
Off topic	0

4 of 17 references resolved; the rest could not be looked up either way.

Hereditary Spastic Paraplegia 7

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Hereditary Spastic Paraplegia 7 (SPG7) — Comprehensive Disease Research Report

1. Disease Information

2. Etiology

Disease Causal Factors

Risk Factors

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Ontology Term Suggestions for KB Curation

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