Abstract Background Transthyretin amyloidosis is a life-threatening disorder caused by the deposition of TTR amyloid in various tissues and organs. The most common worldwide pathogenic variant with almost exclusive cardiac involvement is Val122Ile (rs76992529), with an allele frequency of 3.5% in the U.S. African-American population, but rare in Caucasians. Unexpectedly, we identified 23 Caucasian individuals with Val122Ile in our amyloidosis referral center (9 affected patients, 14 carriers), belonging to 9 unrelated families. Purpose To determine the ancestral origin of the Tuscan founder population of TTR Val122Ile carriers. Methods A total of 24 individuals were included in the analysis (our 23 probands and relatives from Val122Ile families and the Caucasian reference sample NA10851 (CEU – Utah resident with European ancestry). All samples were genotyped using the EUROFORGEN Global AIM-SNP array1, inclusive of 127 highly informative SNPs to infer genetic ancestry. We have performed a principal component analysis (PCA) of the 9 unrelated probands and NA10851, compared with the Phase 3 of the 1000 Genomes Project data, comprising 2504 unrelated individuals from >20 distinct populations.(Figure 1). Results As shown in Figure 1, all our samples but one (from Argentina) cluster very close to the super-cluster of European populations, and distant from the populations of African ancestry. The proband from Argentina and the Caucasian reference sample NA10851 cluster close to Mexicans and Peruvians, and the super-cluster of European populations, respectively, confirming the robustness of the analysis. Conclusion Based on this result, we can confidently conclude that our samples from Tuscan families in which the TTR Val122Ile variant segregates are of ancestral European origin, with no mixed African ancestry, implying that the same variant originated in Africans and Europeans independently and not as result of genetic admixture. These findings suggest the presence of a mutational hot spots in TTR, with potential impact on the epidemiology of amyloidosis worldwide. Acknowledgement/Funding The present study was supported by an Investigator-Initiated Research to Azienda Ospedaliero Universitaria Careggi from Pfizer Srl.