200. Congenital Myasthenic Syndromes Flashcards
What are congenital myasthenic syndromes (CMSs)?
Rare disorders caused by hereditary mutations affecting the neuromuscular junction
How are CMSs typically inherited?
Autosomal recessive manner, except for slow-channel CMS which is autosomal dominant
What are the three main categories of CMS?
- Presynaptic
- Postsynaptic
- Synaptic
What characterizes presynaptic CMS?
Mutations on the nerve side of the junction leading to inadequate release of ACh
What is the most common type of CMS?
Postsynaptic CMS
What are the subtypes of postsynaptic CMS?
- Fast-channel CMS
- Slow-channel CMS
- AChR deficiency
- Inadequate clustering of AChRs
- Disorders of glycosylation
What causes fast-channel CMS?
AChRs close too soon
What causes slow-channel CMS?
AChRs stay open for too long
What is a characteristic feature of synaptic CMS?
Deficiency in acetylcholinesterase
What are common clinical features of CMS?
Fatigable muscle weakness, particularly affecting eye and bulbar muscles
What is correlated with earlier onset of CMS?
Increased severity of symptoms
What demographic has a prevalence of CMS according to Parr et al.?
9.2 children per million, with equal distribution between genders
What is the first step in diagnosing CMS?
Detailed history consistent with symptoms like ptosis and delayed motor milestones
What tests are typically performed to diagnose CMS?
- Physical examination
- Blood tests to rule out antibodies
- Electrodiagnostic testing
- Tensilon test
True or False: CMS responds to steroids or immune modulation.
False
