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ORPHA:101001

Autosomal recessive spastic paraplegia type 21

medium confidenceDisorder

Also known as: Mast syndrome · SPG21

Publications

291

67.1th percentile

Trials

0

Interventional, condition-specific

Researchers

1,459

Distinct authors in sample

Gene link

SPG21

Strong

Readiness

5/6

Stages with a signal

Clinical definition (Orphanet)

spastic paraplegia type 21 is a complex type of spastic paraplegia characterized by an onset in adolescence or adulthood of slowly spastic paraparesis associated with the additional manifestations of apraxia, cognitive and speech decline (leading to dementia and akinetic mutism in some cases), personality disturbances and extrapyramidal (e.g. oromandibular dyskinesia, rigidity) and cerebellar (i.e. dysdiadochokinesia and incoordination) signs. Subtle abnormalities (e.g. developmental delays) may be noted earlier in childhood. A thin corpus callosum and white matter abnormalities are equally reported on magnetic resonance imaging.

How rare: <1 / 1 000 000 — fewer than one in a million. In a city the size of Kolkata, that might mean on the order of fifteen people.

Orphanet entry

Cross-references

Joined from Mondo / Orphanet. MeSH labels may enter searches; UMLS / OMIM / NCIT are stored for reference.

Additional Mondo synonyms (2)

autosomal recessive spastic paraplegia type 21 · mast syndrome

Research stages

Trial readiness signals

Where this condition sits on an open-data research pipeline — not how close a treatment is, and not medical advice. Empty stages often mean “not in these databases under this Mondo ID,” not “impossible.”

5/6 stages with a signal

No specific-condition interventional trial, but broader-category trials exist — discuss eligibility with a clinician.

  1. Gene identifiedPresent

    Strong — SPG21

  2. LiteraturePresent

    291 matched papers (188 in last 10 years) Source

  3. Phenotype characterisedPresent

    42 HPO annotations (e.g. Motor delay; Thin corpus callosum; Lower limb muscle weakness) Source

  4. Animal modelPresent

    1 genotype model (Mus musculus) Source

  5. Orphan designationNot found

    No FDA or EMA orphan-drug designation matched this disease via UMLS or preferred name Source

  6. Interventional trialPartial

    None under the specific name; 104 for broader category paraplegia

Biology

Genes and phenotypes

Gene–disease validity from GenCC, plus phenotypes and animal models joined from Monarch Initiative via Mondo ID — not a clinical diagnosis aid.

Do we know what causes it?

Yes — we know a specific gene responsible (SPG21).

GenCC classification: Strong.

Phenotypes (Monarch / HPO)

42

Associated phenotypes · MONDO:0009568

  • Motor delay
  • Thin corpus callosum
  • Lower limb muscle weakness
  • Athetosis
  • Apraxia

Showing 5 of 42 — open Monarch for the full list.

Animal models (Monarch / Alliance)

1

Model associations linked to this Mondo ID

Monarch fetch 2026-07-29

Therapies

Designations, candidates, and chemicals

FDA OOPD and EMA orphan designations, Open Targets clinical candidates, and CTD chemical associations via MyDisease.info. These never change the interventional-trial headline.

Orphan designation (FDA · EMA)

No designation matched this disease via UMLS or preferred name on the FDA OOPD mirror or EMA orphan register. Absence here is not proof that none exists under another wording.

Open Targets candidates

No drugs or clinical candidates returned for this Mondo ID on Open Targets.

CTD chemicals (MyDisease.info)

No CTD chemical associations returned for this Mondo ID.

Literature

Is anyone studying this?

291

291 papers have ever been published on this condition (under this name). For scale, breast cancer has over 700,000. Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=3967) is 59.

291 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 59 (publications denominator n=3967).

188 in the last 10 years · medium confidence · 67.1th percentile (publications denominator)

Phrase hits: 291 · MeSH hits: 1

Open Europe PMC search

Who's working on it?

1,459

Distinct author names in 200 sampled papers — named people below.

Who's working on it?

No interventional trial matched this name; these authors publish on it in the sampled literature — a practical starting point for contact.

  1. 01
    Blackstone C8 papers · 2025

    Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 35, Room 2A-201, 9000 Rockville Pike, Bethesda, MD 20892, USA. Electronic address: blackstc@ninds.nih.gov.

    Papers in Europe PMC
  2. 02
    Stevanin G7 papers · 2021

    Institut du Cerveau et de la Moelle épinière, INSERM U1127, CNRS UMR7225, Sorbonne Universités, UPMC Université Paris VI UMR_S1127, Paris, France. giovanni.stevanin@upmc.fr.

    Papers in Europe PMC
  3. 03
    Brice A4 papers · 2016

    Institut du Cerveau et de la Moelle épinière, INSERM U1127, CNRS UMR7225, Sorbonne Universités, UPMC Université Paris VI UMR_S1127, Paris, France. alexis.brice@upmc.fr.

    Papers in Europe PMC
  4. 04
    Crosby AH4 papers · 2005
    Papers in Europe PMC
  5. 05
    Ma Y4 papers · 2026

    Key Laboratory of Ruminant Molecular and Cellular Breeding, School of Agriculture, Ningxia University, Yinchuan, China.

    Papers in Europe PMC
  6. 06
    Wang X4 papers · 2023

    Department of Minimally Invasive Spine Surgery, Luoyang Orthopedic-Traumatological Hospital, QiMing Road, LuoYang city, China 471002.

    Papers in Europe PMC
  7. 07
    Zhang Y4 papers · 2025

    Department of Geriatrics, The Fifth Affiliated Hospital Sun Yat-Sen University, Zhuhai 519000, China.

    Papers in Europe PMC
  8. 08
    Boesch S3 papers · 2026

    Center for Rare Movement Disorders, Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria. sylvia.Boesch@i-med.ac.at.

    Papers in Europe PMC
  9. 09
    Chen Y3 papers · 2023

    Department of Environmental Health Sciences, Yale School of Public Health, Yale School of Medicine, New Haven, CT 06520, United States.

    Papers in Europe PMC
  10. 10
    Durr A3 papers · 2016

    Institut du Cerveau et de la Moelle épinière, INSERM U1127, CNRS UMR7225, Sorbonne Universités, UPMC Université Paris VI UMR_S1127, Paris, France.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

0

interventional trials for this specific condition

No interventional trial testing a treatment matched this specific condition name on ClinicalTrials.gov (observational studies and pan-disease registries are listed separately when present). 104 trials are registered for paraplegia, the broader category — shown separately because they may or may not enrol this specific subtype.

Data as of 11 September 2026 · last trial check 11 September 2026

No matched interventional trials. This is true for 77.2% of diseases in the trials denominator (5501 of 7126). Here are the researchers publishing on it.

medium confidence · 38.6th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

No interventional trial testing a treatment was found for this specific condition name on ClinicalTrials.gov.

104 interventional trials matched paraplegia, the broader category — listed below. Those studies are not counted in the condition-specific total.

Broader category: paraplegia

104

Interventional trials for the parent category, exclusive of NCT IDs already counted above. Eligibility for this subtype is not guaranteed.

Worth raising with a clinician. How we count trials.

Recruiting under the broader category

Other registries (secondary)

Broader net from EU CTIS, ISRCTN, and ICTRP when available — deduped against ClinicalTrials.gov IDs already counted above. Dual-model LLM relevance gates what we keep. These rows are not added to the interventional headline.

raw 8 · after dedupe 8 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 8 · dropped 0 · fetched 2026-07-30

Source notes: ictrp: Error: ICTRP public search unavailable (WHO portal is SPA-only; SOAP needs partnership). Tried: https://apps.who.int/tri

No secondary-registry studies passed dual-model relevance for this condition name (after dedupe).

Uncertain / not reviewed (8)

Where to find support

Condition-specific patient organisations, when Orphanet lists them, are on the disease’s Orphanet page. We also link umbrella groups that support undiagnosed and ultra-rare families.

Orphanet entry for Autosomal recessive spastic paraplegia type 21 — check Associations / patient organisations on that page.

India — NPRD

Last verified 2026-07-26

This ORPHAcode is not on our curated NPRD list (direct or Mondo-parent match). That does not decide clinical eligibility; families in India should ask a notified Centre of Excellence about current coverage.

Hand-curated for this project. ORPHAcode mappings are best-effort and may be incomplete or imprecise for umbrella categories. Parent (Mondo) matches mean the policy lists a broader category — confirm eligibility with a Centre of Excellence. Financial entitlements summarised from public policy statements and may change. This is not official government guidance.

How we counted this

Europe PMC query (preferred label + any corrected label + Orphanet and Mondo exact synonyms, stoplisted; unioned with resolved MeSH labels when available). UMLS / OMIM / NCIT cross-references are stored on the overview but are not added to the query string.

("Autosomal recessive spastic paraplegia type 21" OR "Mast syndrome" OR "SPG21") OR (MESH:"MAST Syndrome") OR ("SPG21 syndrome" OR "SPG21-related")

Run this search on Europe PMC

MeSH descriptor terms unioned into the query: MAST Syndrome

ClinicalTrials.gov query (quoted phrases + MeSH via query.cond, plus recall-expansion terms when used):

"Autosomal recessive spastic paraplegia type 21" OR "Mast syndrome" OR "SPG21"

Study-type breakdown: 0 interventional · 0 observational · 0 expanded access. Only interventional studies enter the trial headline.

Parent-category trials query:

"paraplegia"

Query health: ok — strategies attempted: phrase, mesh; with hits: phrase, mesh

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is multi-word and distinctive
  • No synonyms dropped by stoplist
  • No label/synonym collisions with other diseases in this corpus
  • Publication count (291) is high for prevalence class "<1 / 1 000 000" — confidence capped at medium

Ingested 2026-07-27T07:11:01.865Z