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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

1/6

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.”

1/6 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 characterisedNot checked

    Not yet enriched from Monarch / HPO

  4. Animal modelNot checked

    Not yet enriched from Monarch / Alliance

  5. Orphan designationNot checked

    FDA/EMA orphan-drug designation not enriched yet

  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)

Not enriched in this build — Monarch phenotype joins were not run for this record.

Animal models (Monarch / Alliance)

Not enriched in this build.

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=5449) is 41.

2,236 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 41 (publications denominator n=5449).

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 27 July 2026

No matched interventional trials. This is true for 73% of diseases in the trials denominator (5114 of 7003). Here are the researchers publishing on it.

low confidence · 36.5th 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

Where to find support

We do not yet link condition-specific patient organisations. These umbrella groups support undiagnosed and ultra-rare families:

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