Reported is a patient with a congenital myasthenic syndrome due to two compound heterozygous mutations of the CHRNE gene. The molecular consequences of a novel intronic base alteration ( CHRNE IVS5-16G -> A) remote from the splice acceptor site were investigated in vivo and in vitro. In conclusion, RNA analysis may be necessary to reveal unexpected splicing aberrations due to intronic mutations that are not part of the consensus splice site.