We report a patient with familial amyloid polyneuropathy. Gene analysis revealed a heterozygous Glu54Gly substitution (A-to-G change) in the transthyretin gene. This is the first case of a Glu54Gly substitution that was devoid of a Gly6Ser substitution. Compared with the previously reported case with compound heterozygotes of Glu54Gly and Gly6Ser, the age of onset in our case is much younger and another characteristic findings were the amyloid vasculopathy and the multiple organ involvement. A Glu54Gly mutation is amyloidogenic by itself and a Gly6Ser mutation may offer some protection from the Glu54Gly mutant.