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ORPHA:84142

Isaacs syndrome

low confidenceDisorder

Also known as: Continuous muscle fiber activity syndrome · Isaacs-Mertens syndrome · Quantal squander syndrome

Publications

2,236

Trials

0

Interventional, condition-specific

Researchers

1,027

Distinct authors in sample

Gene link

—

Readiness

2/6

Stages with a signal

Clinical definition (Orphanet)

Isaac's syndrome is an immune-mediated peripheral motor neuron disorder characterized by continuous muscle fiber activity at rest resulting in muscle stiffness, cramps, myokymia, and pseudomyotonia.

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 (6)

Isaacs' syndrome · acquired neuromyotonia · continuous muscle fiber activity syndrome · continuous muscle fibre activity syndrome · neuromyotonia · peripheral nerve hyperexcitability

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.”

2/6 stages with a signal

Research-stage checklist from open sources (GenCC, literature, Monarch when enriched, ClinicalTrials.gov). Not a prognosis or care recommendation.

  1. Gene identifiedNot found

    No GenCC disease–gene assertion in this build

  2. LiteraturePresent

    2,236 matched papers (1,118 in last 10 years) Source

  3. Phenotype characterisedPresent

    13 HPO annotations (e.g. Weight loss; Myokymia; EEG abnormality) 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 trialNot found

    No matched interventional trial under our ClinicalTrials.gov rules

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?

Not yet — the cause hasn't been pinned down in GenCC.

No strong gene–disease assertion joined for this Orphanet entity.

Phenotypes (Monarch / HPO)

13

Associated phenotypes · MONDO:0019399

  • Weight loss
  • Myokymia
  • EEG abnormality
  • Fasciculations
  • Muscle spasm

Showing 5 of 13 — 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)

4 associated chemicals. Therapeutic evidence is listed first when present — not a treatment recommendation.

  • Azathioprine · therapeutic
  • Carbamazepine · therapeutic
  • Phenytoin · therapeutic
  • Penicillamine · marker/mechanism

MyDisease.info · MONDO:0019399

Literature

Is anyone studying this?

2,236

2,236 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.

2,236 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).

1,118 in the last 10 years · low confidence

Phrase hits: 2,236 · MeSH hits: 0

Open Europe PMC search

Who's working on it?

1,027

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
    Irani SR5 papers · 2025

    Oxford Autoimmune Neurology Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK sarosh.irani@ndcn.ox.ac.uk.

    Papers in Europe PMC
  2. 02
    Joubert B5 papers · 2025

    From the French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Hospices Civils de Lyon; Synaptopathies and Autoantibodies (SynatAc) Team (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Institut NeuroMyoGène, MELIS, INSERM U1314/CNRS UMR 5284, Université Claude Bernard Lyon 1; Epileptology-EEG Department (J.B.), Neurology, Pasteur2 Hospital, University Hospitals of Nice; Côte d'Azur University (J.B.), UR2CA, URRIS, Pasteur2 Hospital, University Hospitals of Nice; Department of Functional Neurology and Epileptology (D.G., S.R.), Hospices Civils de Lyon, France; European Network for Rare and Complex Epilepsies (EPICARE) (D.G., S.R.); Service de Neurologie 2-Mazarin (A.A., D.P.), Hôpitaux Universitaires La Pitié-Salpêtrière-Charles Foix, APHP; Inserm U1127 CNRS UMR 7225 (A.A., D.P.), Institut Du Cerveau et de la Moelle épinière, ICM, Université Pierre-et-Marie-Curie, Sorbonne Universités, Paris; and Lyon's Neuroscience Research Center (S.R.), INSERM U1028/CNRS UMR 5292; Université Lyon 1 Claude Bernard, France. bastien.joubert@chu-lyon.fr.

    Papers in Europe PMC
  3. 03
    Watanabe O5 papers · 2025

    Department of Neurology, Research and Education Assembly Medical and Dental Sciences Area Medical and Dental Hospital.

    Papers in Europe PMC
  4. 04
    Waters P5 papers · 2026

    Oxford Autoimmune Neurology Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.

    Papers in Europe PMC
  5. 05
    Honnorat J4 papers · 2025

    From the French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Hospices Civils de Lyon; Synaptopathies and Autoantibodies (SynatAc) Team (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Institut NeuroMyoGène, MELIS, INSERM U1314/CNRS UMR 5284, Université Claude Bernard Lyon 1; Epileptology-EEG Department (J.B.), Neurology, Pasteur2 Hospital, University Hospitals of Nice; Côte d'Azur University (J.B.), UR2CA, URRIS, Pasteur2 Hospital, University Hospitals of Nice; Department of Functional Neurology and Epileptology (D.G., S.R.), Hospices Civils de Lyon, France; European Network for Rare and Complex Epilepsies (EPICARE) (D.G., S.R.); Service de Neurologie 2-Mazarin (A.A., D.P.), Hôpitaux Universitaires La Pitié-Salpêtrière-Charles Foix, APHP; Inserm U1127 CNRS UMR 7225 (A.A., D.P.), Institut Du Cerveau et de la Moelle épinière, ICM, Université Pierre-et-Marie-Curie, Sorbonne Universités, Paris; and Lyon's Neuroscience Research Center (S.R.), INSERM U1028/CNRS UMR 5292; Université Lyon 1 Claude Bernard, France.

    Papers in Europe PMC
  6. 06
    Li J4 papers · 2026

    Department Neurology, Xiangya Hospital, Central South University, Changsha, 410008, China.

    Papers in Europe PMC
  7. 07
    Vincent A4 papers · 2020

    Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.

    Papers in Europe PMC
  8. 08
    Farina A3 papers · 2025

    From the French Reference Center on Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Hospices Civils de Lyon; Synaptopathies and Autoantibodies (SynatAc) Team (J.B., S.M.-C., A.V., A.F., A.-L.P., G.P., V.R., J.H., B.J.), Institut NeuroMyoGène, MELIS, INSERM U1314/CNRS UMR 5284, Université Claude Bernard Lyon 1; Epileptology-EEG Department (J.B.), Neurology, Pasteur2 Hospital, University Hospitals of Nice; Côte d'Azur University (J.B.), UR2CA, URRIS, Pasteur2 Hospital, University Hospitals of Nice; Department of Functional Neurology and Epileptology (D.G., S.R.), Hospices Civils de Lyon, France; European Network for Rare and Complex Epilepsies (EPICARE) (D.G., S.R.); Service de Neurologie 2-Mazarin (A.A., D.P.), Hôpitaux Universitaires La Pitié-Salpêtrière-Charles Foix, APHP; Inserm U1127 CNRS UMR 7225 (A.A., D.P.), Institut Du Cerveau et de la Moelle épinière, ICM, Université Pierre-et-Marie-Curie, Sorbonne Universités, Paris; and Lyon's Neuroscience Research Center (S.R.), INSERM U1028/CNRS UMR 5292; Université Lyon 1 Claude Bernard, France.

    Papers in Europe PMC
  9. 09
    Katirji B3 papers · 2026

    Neuromuscular Center and EMG Laboratory, Neurological Institute, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland, OH, United States. Electronic address: bashar.katirji@uhhospitals.org.

    Papers in Europe PMC
  10. 10
    Liu Y3 papers · 2025

    Department of Neurology, Inner Mongolia Autonomous Region People's Hospital, No.20, Zhaowuda Road, Hohhot, 010017, Inner Mongolia, China.

    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. 1 observational study did — shown below because natural-history and cohort work can be an important step toward a trial.

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.

See who's working on it — people publishing on this disease are often the practical next contact when no trial is listed.

Observational and natural-history studies

1 observational study matches this condition. These do not test a treatment and are not counted in the interventional-trial headline, but they are genuine research: natural-history work often defines the endpoints needed for a future rare-disease trial, and families may be able to enroll.

None of the matched observational studies is currently listed as recruiting.

Open the complete matched search on ClinicalTrials.gov

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 0 · after dedupe 0 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 0 · 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).

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 Isaacs syndrome — 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.

"Isaacs syndrome" OR "Continuous muscle fiber activity syndrome" OR "Isaacs-Mertens syndrome" OR "Quantal squander syndrome" OR "Isaacs' syndrome" OR "acquired neuromyotonia" OR "continuous muscle fibre activity syndrome" OR "neuromyotonia" OR "peripheral nerve hyperexcitability"

Run this search on Europe PMC

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

"Isaacs syndrome" OR "Continuous muscle fiber activity syndrome" OR "Isaacs-Mertens syndrome" OR "Quantal squander syndrome" OR "Isaacs' syndrome" OR "acquired neuromyotonia" OR "continuous muscle fibre activity syndrome" OR "neuromyotonia" OR "peripheral nerve hyperexcitability"

Study-type breakdown: 0 interventional · 1 observational · 0 expanded access. Only interventional studies enter the trial headline.

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

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is short or not clearly distinctive
  • No synonyms dropped by stoplist
  • "Isaacs-Mertens syndrome" also appears on ORPHA:37612
  • Publication count (2236) is implausibly high for prevalence class "<1 / 1 000 000" — treat as possible over-matching, not a measure of research intensity

Ingested 2026-07-27T02:44:09.981Z