Congenital myasthenic syndromes (CMS) are characterized by fatigable weakness involving ocular, bulbar, and limb muscles with onset at or shortly after birth or in early childhood; rarely, symptoms may not manifest until later in childhood. CMS is limited to weakness of the skeletal muscles: cardiac and smooth muscle are not involved. Some medications may be helpful, but motor milestones can be delayed. Congenital myasthenic syndromes are inherited in an autosomal recessive, or, less frequently, autosomal dominant manner.