Increased Risk of Multiple Outpatient Surgeries in African-American Carriers of Transthyretin Val122Ile Mutation Is Modulated by Non-Coding Variants

Background: African-Americans (AAs) have a 3.5% carrier prevalence of Transthyretin (TTR) Val122Ile mutation (rs76992529), which is the genetic cause of a hereditary form of amyloidosis. Methods: We investigated the medical history of Val122Ile carriers and assessed the role of a non-coding variation in 4361 unrelated AAs. Results: We observed that the Ile122 allele was associated with a 6.8-fold increase in the odds of having 10 or more outpatient surgeries (p = 7.81 × 10^-5). Stratifying the analysis by sex, the Ile122 allele was associated with a 15.2-fold increase in the odds of having 10 or more outpatient surgeries in men (p = 6.49 × 10^-7). A similar sex difference was observed with respect to the association of Val122Ile with musculoskeletal and connective-tissue disorders in an independent cohort of British subjects (n = 361,194, p = 2.47 × 10^-13; n_male = 167,020, p_male = 4.02 × 10^-24). In Val122Ile African-American carriers, we observed that haplotypes in the upstream region regulating TTR hepatic expression are associated with having 10 or more outpatient surgeries (p = 2.56 × 10^-9). Conclusions: TTR Val122Ile showed a large effect with respect to an extreme phenotype identified in medical history that may be related to osteoarthritis, an early sign of the disease. Additionally, the non-coding variation appears to accelerate the negative consequences associated with Val122Ile mutation via TTR expression regulation.