To present the genetic heterogeneity of a sample of the Brazilian population with transthyretin (TTR) mutations. This cohort study was descriptive and retrospective, and enrolled patients with peripheral neuropathy of unknown cause that were found to have a mutation in the TTR gene during the process of etiological investigation, between July 1997 to January 2016. Over the study period, 129 point mutations were identified in 448 tested patients, of whom 128 were of Brazilian origin. The TTR Val30Met mutation was identified in 116 patients (90.6%); while 7 (4.7%) patients had a pathogenic non-TTR mutation and 7 (4.7%) carried non-pathogenic mutations (4.7%). The four non-TTRMet30 pathogenic mutations were TTR Aps38Tyr; TTR Ile107Val; TTR Val71Ala; and TTR Val122Ile. In the non-pathogenic group, we only found two mutations, including TTR Gly6Ser and TTR Thr119Thr. Our study depicts a scenario of greater genetic heterogeneity among Brazilian hereditary transthyretin amyloidosis (hATTR) patients with familial amyloidotic polyneuropathy (FAP). We expect that this number will grow fast over a short period of time, due to increasing availability of genetic tests, increasing knowledge of the disease and the multivariate origin of our population.

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