congenital myasthenic syndrome 2A
Findings
No curated finding names congenital myasthenic syndrome 2A yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
A congenital myasthenic syndrome characterized by autosomal dominant inheritance of postsynaptic neuromuscular junction defects, early-onset progressive muscle weakness, and prolonged opening and activity of the acetylcholine receptor channel that has material basis in heterozygous mutation in the CHRNB1 gene on chromosome 17p13.
Definition from the Mondo Disease Ontology (MONDO:0014581), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal dominant inheritance
HPO, annotations 2026-09-02
Features
21 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Abnormally high-pitched voiceHPOHP:0001620
- 1 of 1 reported patient
- Delayed ability to sitHPOHP:0025336
- 1 of 1 reported patient
- Delayed ability to walkHPOHP:0031936
- 1 of 1 reported patient
- Easy fatigabilityHPOHP:0003388
- 1 of 1 reported patient
- EMG: decremental response of compound muscle action potential to repetitive nerve stimulationHPOHP:0003403
- 1 of 1 reported patient
- Fatigable weaknessHPOHP:0003473
- 1 of 1 reported patient · Congenital onset
- Flexion contracture
Show the remaining 9
- Muscle fiber splittingHPOHP:0003555
- 1 of 1 reported patient
- OphthalmoplegiaHPOHP:0000602
- 1 of 1 reported patient · Juvenile onset
- Poor head controlHPOHP:0002421
- 1 of 1 reported patient · Infantile onset
- Poor suckHPOHP:0002033
- 1 of 1 reported patient
- PtosisHPOHP:0000508
- 1 of 1 reported patient
- Skeletal muscle atrophyHPOHP:0003202
- 1 of 1 reported patient
Genes
1 gene
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- CHRNB1HGNC:1961
- Strong · Genomics England PanelApp · Autosomal dominant · 2021
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal dominant · 2021
- Moderate · Ambry Genetics · Autosomal dominant · 2024
- Moderate · ClinGen · Autosomal dominant · 2025
Where it sits
Other names
2 names
Resolves to: congenital myasthenic syndrome 2A
- Also called
- CMS2Acongenital myasthenic syndrome type 2A