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. [ http://purl.obolibrary.org/obo/ECO_0007645 ]