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ORPHA:1145

Infantile-onset X-linked spinal muscular atrophy

low confidenceDisorder

Also known as: SMAX2 · Spinal muscular atrophy with arthrogryposis · X-linked distal arthrogryposis multiplex congenita · X-linked spinal muscular atrophy type 2

Publications

3,976

Trials

0

Interventional, condition-specific

Researchers

482

Distinct authors in sample

Gene link

UBA1

Strong

Readiness

4/6

Stages with a signal

Clinical definition (Orphanet)

A rare form of spinal muscular atrophy characterized by the onset of severe , areflexia, profound weakness, multiple contractures, facial features (myopathic face with open, tent-shaped mouth), cryptorchidism, and mild skeletal abnormalities (i.e. kyphosis, scoliosis), that is often preceded by polyhydramnios and reduced fetal movements in utero and followed by bone fractures shortly after birth. Muscle weakness is and chest muscle involvement eventually leads to ventilatory insufficiency and respiratory failure.

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 (3)

spinal muscular atrophy with arthrogryposis · spinal muscular atrophy, X-linked 2, infantile, X-linked recessive · spinal muscular atrophy, X-linked type 2

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.”

4/6 stages with a signal

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

  1. Gene identifiedPresent

    Strong — UBA1

  2. LiteraturePresent

    3,976 matched papers (2,988 in last 10 years) Source

  3. Phenotype characterisedPresent

    65 HPO annotations (e.g. Poor suck; Degeneration of anterior horn cells; Skeletal muscle atrophy) Source

  4. Animal modelNot found

    No Alliance genotype “model of” associations via Monarch for these Mondo IDs

  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; 166 for broader category spinal muscular atrophy

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 (UBA1).

GenCC classification: Strong.

Phenotypes (Monarch / HPO)

65

Associated phenotypes · MONDO:0010532

  • Poor suck
  • Degeneration of anterior horn cells
  • Skeletal muscle atrophy
  • EMG: neuropathic changes
  • Abnormal muscle fiber morphology

Showing 5 of 65 — open Monarch for the full list.

Animal models (Monarch / Alliance)

None returned for this Mondo ID. Empty here is not proof that no model organism work exists under another name or gene.

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?

3,976

3,976 papers have been published on this condition. That is a real research literature — still far smaller than common diseases (breast cancer: over 700,000 papers). Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=3967) is 59.

3,976 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).

2,988 in the last 10 years · low confidence

Phrase hits: 80 · MeSH hits: 0

Open Europe PMC search

Who's working on it?

482

Distinct author names in 80 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
    Demontis F3 papers · 2026

    Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105, USA. Fabio.Demontis@stjude.org.

    Papers in Europe PMC
  2. 02
    Gaudet R3 papers · 2019

    Cambridge, MA.

    Papers in Europe PMC
  3. 03
    Ahearn ME2 papers · 2017

    Translational Genomics Research Institute (TGen), Phoenix, Arizona, 85004, USA.

    Papers in Europe PMC
  4. 04
    Baumbach-Reardon L2 papers · 2017

    Translational Genomics Research Institute (TGen), Phoenix, Arizona, 85004, USA.

    Papers in Europe PMC
  5. 05
    Bennett AH2 papers · 2019

    Department of Molecular and Cellular Biology (J.V., R.G.), Harvard University, Cambridge; Division of Genetics (M.M.M., A.T.-P., C.G., A.H.B., N.C., B.T.D., N.Y.F., J.K., V.A.G.), Brigham Genomic Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston; Division of Genetics (E.E.), Boston Children's Hospital; and Division of Neurology (B.T.D.), Boston Children's Hospital, Harvard Medical School, MA.

    Papers in Europe PMC
  6. 06
    Carmichael N2 papers · 2019

    Department of Molecular and Cellular Biology (J.V., R.G.), Harvard University, Cambridge; Division of Genetics (M.M.M., A.T.-P., C.G., A.H.B., N.C., B.T.D., N.Y.F., J.K., V.A.G.), Brigham Genomic Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston; Division of Genetics (E.E.), Boston Children's Hospital; and Division of Neurology (B.T.D.), Boston Children's Hospital, Harvard Medical School, MA.

    Papers in Europe PMC
  7. 07
    Curley M2 papers · 2026

    Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105, USA.

    Papers in Europe PMC
  8. 08
    Darras BT2 papers · 2019

    Department of Molecular and Cellular Biology (J.V., R.G.), Harvard University, Cambridge; Division of Genetics (M.M.M., A.T.-P., C.G., A.H.B., N.C., B.T.D., N.Y.F., J.K., V.A.G.), Brigham Genomic Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston; Division of Genetics (E.E.), Boston Children's Hospital; and Division of Neurology (B.T.D.), Boston Children's Hospital, Harvard Medical School, MA.

    Papers in Europe PMC
  9. 09
    Estrella E2 papers · 2019

    Department of Molecular and Cellular Biology (J.V., R.G.), Harvard University, Cambridge; Division of Genetics (M.M.M., A.T.-P., C.G., A.H.B., N.C., B.T.D., N.Y.F., J.K., V.A.G.), Brigham Genomic Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston; Division of Genetics (E.E.), Boston Children's Hospital; and Division of Neurology (B.T.D.), Boston Children's Hospital, Harvard Medical School, MA.

    Papers in Europe PMC
  10. 10
    Frank NY2 papers · 2019

    Department of Molecular and Cellular Biology (J.V., R.G.), Harvard University, Cambridge; Division of Genetics (M.M.M., A.T.-P., C.G., A.H.B., N.C., B.T.D., N.Y.F., J.K., V.A.G.), Brigham Genomic Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston; Division of Genetics (E.E.), Boston Children's Hospital; and Division of Neurology (B.T.D.), Boston Children's Hospital, Harvard Medical School, MA.

    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). 166 trials are registered for spinal muscular atrophy, 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.

low 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.

166 interventional trials matched spinal muscular atrophy, the broader category — listed below. Those studies are not counted in the condition-specific total.

Broader category: spinal muscular atrophy

166

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 1 · after dedupe 1 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 1 · dropped 0 · fetched 2026-07-29

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 (1)

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 Infantile-onset X-linked spinal muscular atrophy — check Associations / patient organisations on that page.

India — NPRD

Last verified 2026-07-26

Likely covered — the policy lists Spinal muscular atrophy as a category (Group 3), and this condition is a form of it. Confirm eligibility with a Centre of Excellence.

Group 3 — high-cost / lifelong therapy with careful selection

Up to ₹50 lakh per patient

Financial support at notified Centres of Excellence is the figure commonly cited in recent MoHFW/PIB statements. Many Group 3 patients also use the MoHFW voluntary-contribution / crowdfunding portal.

Eligibility and patient selection rules change. Verify with a CoE; the crowdfunding portal is a separate mechanism from CoE funding. Verify

Centres of Excellence (15)
  • All India Institute of Medical Sciences (AIIMS) — New Delhi, Delhi
  • Maulana Azad Medical College — New Delhi, Delhi
  • Sanjay Gandhi Post Graduate Institute of Medical Sciences — Lucknow, Uttar Pradesh
  • Post Graduate Institute of Medical Education and Research (PGIMER) — Chandigarh, Chandigarh
  • Centre for DNA Fingerprinting & Diagnostics with Nizam’s Institute of Medical Sciences — Hyderabad, Telangana
  • King Edward Memorial Hospital — Mumbai, Maharashtra
  • Institute of Post-Graduate Medical Education and Research (IPGMER) — Kolkata, West Bengal
  • Centre for Human Genetics with Indira Gandhi Hospital — Bengaluru, Karnataka
  • Institute of Child Health and Hospital for Children (ICH & HC) — Chennai, Tamil Nadu
  • All India Institute of Medical Sciences (AIIMS) — Jodhpur, Rajasthan
  • Sree Avittam Thirunal Hospital (SAT), Government Medical College — Thiruvananthapuram, Kerala
  • All India Institute of Medical Sciences (AIIMS) — Bhopal, Madhya Pradesh
  • Regional Institute of Medical Sciences (RIMS) — Imphal, Manipur
  • All India Institute of Medical Sciences (AIIMS) — Patna, Bihar
  • Assam Medical College & Hospital — Dibrugarh, Assam

Voluntary contributions / crowdfunding (separate from CoE funding): https://rarediseases.mohfw.gov.in/

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.

("Infantile-onset X-linked spinal muscular atrophy" OR "SMAX2" OR "Spinal muscular atrophy with arthrogryposis" OR "X-linked distal arthrogryposis multiplex congenita" OR "X-linked spinal muscular atrophy type 2" OR "spinal muscular atrophy, X-linked 2, infantile, X-linked recessive" OR "spinal muscular atrophy, X-linked type 2") OR ("UBA1" OR "UBA1 syndrome" OR "UBA1-related")

Run this search on Europe PMC

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

"Infantile-onset X-linked spinal muscular atrophy" OR "SMAX2" OR "Spinal muscular atrophy with arthrogryposis" OR "X-linked distal arthrogryposis multiplex congenita" OR "X-linked spinal muscular atrophy type 2" OR "spinal muscular atrophy, X-linked 2, infantile, X-linked recessive" OR "spinal muscular atrophy, X-linked type 2"

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

Parent-category trials query:

"spinal muscular atrophy"

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

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 (3976) is implausibly high for prevalence class "<1 / 1 000 000" — treat as possible over-matching, not a measure of research intensity

Ingested 2026-07-26T16:30:41.423Z