Congenital Myasthenic Syndromes

Congenital myasthenic syndromes (CMS) are uncommon inherited disorders of the neuromuscular junction. Transmission defects can be at the presynaptic, synaptic (basal lamina-associated), or postsynaptic (acetylcholine receptor, endplate development, and maintenance or defects of glycosylation) sites. Early-life presentations are common, though late onset has been described. Clinical clues like episodic bulbar weakness and apneic spells, delayed pupillary light response, wrist and finger extensor, and neck weakness can point to certain subtypes. CMS needs to be differentiated from myasthenia gravis, Lambert-Eaton myasthenic syndrome, and mitochondriopathies. Response to pyridostigmine, salbutamol, fluoxetine, amifampridine, and quinidine is known, depending on the pathophysiology.