THAOS, an international, longitudinal, observational survey, developed by FoldRx Pharmaceuticals, Inc, (and now supported by Pfizer Inc) in collaboration with clinical disease experts, is designed to characterize the variability, progression, and natural history of TTR amyloidosis, as well as regional differences in disease expression and the genotypic/phenotypic relationship in TTR amyloidosis. The gene discussed is TTR; the disease is familial amyloid neuropathy.