Japanese monozygotic twins with familial amyloidotic polyneuropathy (FAP) (ATTR Val30Met).

Twenty-nine-year-old twin brothers having the amyloidogenic transthyretin (ATTR) Val30Met gene developed the clinical symptoms of familial amyloidotic polyneuropathy (FAP) in 1995. The twins had the same educational background and lived in the same district. FAP manifestations were similar in both cases, although electromyographic examinations revealed sensorimotor polyneuropathy in No. 1 and sensory polyneuropathy in No. 2. DNA analysis revealed that they were monozygotic twins. In addition to environmental factors, genetic factors may play an important role in determining the onset of FAP.