# Genetic and Clinical Spectrum of Hereditary Transthyretin Amyloidosis in Brazil

## TL;DR

This study explores the genetic and clinical diversity of a hereditary amyloidosis disease in Brazil, highlighting regional and ethnic differences in symptom onset.

## Contribution

The study identifies a distinct geographic pattern of disease onset in Brazil and emphasizes the impact of ethnicity on age of onset.

## Key findings

- Seven TTR pathogenic variants were identified in a Brazilian cohort, with p.Val50Met being the most common.
- Late-onset V30M cases are more frequent in Brazil's central region, while early-onset V30M is more common in São Paulo/South.
- Familial cases presented with a 20.5-year earlier age of onset compared to sporadic cases.

## Abstract

Transthyretin hereditary amyloidosis (ATTRv) clinical variability has been widely reported, not only across countries and variants but also among families and distinct regions within a single nation. One of the principal challenges in disease management is the accurate determination of age of onset (AOO), which is heterogeneous and has therapeutic implications given the availability of disease‐modifying treatments.

This study characterizes the genetic landscape and clinical onset spectrum of ATTRv in an admixed Brazilian cohort of 175 patients.

Seven TTR pathogenic variants (p.Val50Met, p.Val142Ile, p.Ile127Val, p.Ile88Leu, p.Ala39Asp, p.Phe84Leu, p.Tyr98Phe) were identified. The most common was p.Val50Met (58.8%), followed by p.Val142Ile (29.7%) and p.Ile127Val (7.4%). Notably, 44% of V122I had a neurological onset. Close clinical monitoring of presymptomatic carriers reduced age at diagnosis by 10.5 years. The median AOO was 50 years, with V30M patients presenting earlier (38.5 years) than V122I (p.Val142Ile) (60y) and I107V (p.Ile127Val) (60 years). Familial cases showed a 20.5‐year earlier AOO than sporadic cases. In Brazil, late‐onset (> 50 years) V30M is more common than previously reported (37.5%); ethnicity can influence AOO within the same variant, and for the first time, we show a distinct geographic pattern: early‐onset V30M is more frequent in São Paulo/South, whereas late‐onset V30M predominates in the central region.

This study emphasizes the heterogeneity of ATTRv presentation in admixed populations and underscores the need for expanded screening and multicenter studies to refine genotype–phenotypic correlations.