TTR and Abnormal autonomic nervous system physiology: However, compared with the common TTR gene mutation-related ATTR that usually began with a length-dependent polyneuropathy, developed more severe autonomic dysfunction (16, 19) and could lead to death within 7–12 years of onset if left untreated (1, 20), Gly83Arg mutation-related ATTR had a relatively more benign prognosis and longer survival.