Neuromuscular

Slow-Channel Congenital Myasthenic Syndrome

Also known as slow-channel CMS, SCCMS, congenital myasthenic syndrome slow channel

Slow-Channel Congenital Myasthenic Syndrome is caused by dominant gain-of-function mutations in genes encoding nicotinic acetylcholine receptor (AChR) subunits, prolonging channel open time and causing calcium-mediated excitotoxic damage to

ORPHA:716765 ↗Gene CHRNA1Gene CHRNB1Gene CHRNDGene CHRNEPrevalence Less than 1 in 500,000Onset Variable; infancy to adulthood (allelic heterogeneity)Autosomal dominant (gain-of-function)

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studies recruiting now

as of 7 Sept 2026

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studies registered in total

as of 7 Sept 2026

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countries with a recruiting site

as of 7 Sept 2026

None

recruiting study posted to date

among recruiting studies

Recruiting trials

No registered studies found for Slow-Channel Congenital Myasthenic Syndrome.

ClinicalTrials.gov has no study listed under this name as of 7 Sept 2026. That can change, and there are other routes worth knowing about.

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Patient organisations

Myasthenia Gravis Foundation of AmericaPatient association
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Registry: CMS Registry (Congenital Myasthenic Syndrome) · Join ↗. Registries connect patients to researchers and often hear about trials first.

About Slow-Channel Congenital Myasthenic Syndrome

Slow-Channel Congenital Myasthenic Syndrome is caused by dominant gain-of-function mutations in genes encoding nicotinic acetylcholine receptor (AChR) subunits, prolonging channel open time and causing calcium-mediated excitotoxic damage to the end-plate and subsynaptic myonuclei. It is distinguished from other CMS subtypes by its dominant inheritance, characteristic end-plate myopathy on biopsy, and selective weakness of cervical, scapular, and finger extensor muscles. It is specifically treated with quinidine or fluoxetine, which shorten channel open time.

Common clinical features

Selective weakness of cervical and scapular musclesFinger extensor weaknessPtosis and ophthalmoparesisFatigable weakness that worsens with activityRepetitive CMAP on single-nerve stimulation (electrodiagnostic hallmark)End-plate myopathy on muscle biopsyVariable bulbar involvement

From Orphanet’s phenotype annotations (CC BY 4.0). Not a complete list.

Before you apply

Things trial teams commonly ask about for Slow-Channel Congenital Myasthenic Syndrome. Not eligibility rules; those are set by each study.

  • Genetic confirmation of a dominant pathogenic AChR subunit mutation is required; AChR antibodies are negative in CMS (differentiating it from myasthenia gravis) — confirm seronegative status in your records
  • Repetitive nerve stimulation (RNS) showing repetitive CMAP and single-fibre EMG showing increased jitter are key diagnostic electrophysiological findings required for most trials
  • Current medications including quinidine or fluoxetine may necessitate washout periods; discuss medication management with your neurologist well before a planned trial application

Related conditions

Information, not medical advice. Trial listings are shown as recorded on ClinicalTrials.gov; whether any study is right for you is a decision for you and your clinicians, and eligibility is decided by each research team. Disease information from Orphanet (CC BY 4.0).