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congenital myasthenic syndrome 21 (CMS21) - Clinical Profile, Genes & Research | Kisho | Kisho

Rare Disease

congenital myasthenic syndrome 21

MONDO:0014983

Also known as:CMS21SLC18A3 congenital myasthenic syndromecongenital myasthenic syndrome 21, presynaptic

Overview

Any congenital myasthenic syndrome in which the cause of the disease is a mutation in the SLC18A3 gene.

GeneticsAutosomal recessive · SLC18A3 (chr 10)

Clinical Presentation

Built from Human Phenotype Ontology (HPO) phenotype annotations and GeneReviews clinical descriptions. Features represent findings documented across known cases — not an exhaustive list of possible symptoms.

Features include always present findings: Ptosis, Ophthalmoplegia, and Exercise intolerance; and common findings: Meconium ileus, Easy fatigability, Feeding difficulties, and Low muscle tone (hypotonia) and others. 17 total HPO annotations.

Organ System	Phenotype Count	Example Features
Brain and nerves	4	Difficulty walking (gait disturbance), Fatigue, Hyperintensity of cerebral white matter on MRI

Genetic Landscape

SLC18A3 function has not been fully characterized.

Congenital myasthenic syndrome 21 is associated with mutations in the SLC18A3 gene on chromosome 10.

Diagnosis

Genetic testing for SLC18A3 is available. Testing is considered confirmatory for diagnosis.

Biomarker and diagnostic research for congenital myasthenic syndrome 21 has been reported in the published literature.

Prognosis

Phenotype severity distribution: 3 always present features, 12 common features.

Research Landscape

Sourced from ClinicalTrials.gov and PubMed. Publication types are classified using NLM-curated article metadata; research type breakdowns reflect the nature of published work for this disease.

No clinical trials have been registered for congenital myasthenic syndrome 21.

17 publications have been identified in PubMed for congenital myasthenic syndrome 21. Research spans Case Report / Case Series (29%), Epidemiology / Natural History (24%), and Review / Meta-Analysis (18%).

Research Type	Count	% of Total
Patient case studies	5	29%

Data assembled from 5 of 12 sources · Last updated Sep 20, 2026, 12:26 PM UTC

MONDOHPOClinicalTrials.govFDAPubMedHGNCClinVarClinGenGeneReviewsOrphanetOMIMRUSP

Medical References

External Resources

OMIM

Online Mendelian Inheritance in Man

OMIM:617239

GARD

Genetic and Rare Diseases Info Center

GARD:16212

Questions for Your Care Team

→Should my partner and I meet with a genetic counselor to discuss carrier status and family planning?
→Are there specialists or centers of excellence for this condition in my area?
→Is there a patient registry I should consider joining?

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congenital myasthenic syndrome 21

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Prognosis

Research Landscape

Medical References

External Resources

OMIM

GARD

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Questions for Your Care Team

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congenital myasthenic syndrome 21

Overview

Clinical Presentation

Genetic Landscape

Diagnosis

Prognosis

Research Landscape

Medical References

External Resources

OMIM

GARD

Related Diseases

Questions for Your Care Team

Questions for Your Care Team

Explore clinical features

Recent Publications