Clinical Presentation and Diagnostic Challenges of Frontotemporal Dementia in Brazil: A 15-Year Cohort Study.

INTRODUCTION

Frontotemporal dementia (FTD) comprises heterogeneous neurodegenerative syndromes with limited data from low- and middle-income countries, where diagnostic delay and misdiagnosis are common.

METHODS

A retrospective cohort study was conducted of 190 patients with FTD meeting criteria for behavioral variant FTD (bvFTD), primary progressive aphasia (PPA), or FTD-amyotrophic lateral sclerosis (FTD-ALS) who were evaluated at a publicly funded Brazilian tertiary referral center (2009-2024). Clinical features, diagnostic trajectories, neuroimaging, genetic testing, and survival outcomes were analyzed. Standardized mortality ratios (SMRs) were calculated using IBGE 2017 life tables as a reference.

RESULTS

The cohort comprised 95 bvFTD (50.0%; 73 probable and 22 possible), 79 PPA (41.6%), and 16 FTD-ALS (8.4%) patients. Accurate initial diagnosis was achieved in only 15.8% of bvFTD patients and 17.7% of PPA patients, with Alzheimer's disease being the most common misdiagnosis (36.8% and 34.2%, respectively). Survival differed significantly between subtypes (p < 0.001), with FTD-ALS having the shortest median survival (79.0 months) compared with PPA (119.0 months) and bvFTD (144.0 months). Compared with PPA, FTD-ALS was associated with increased mortality risk (HR: 4.01; 95% CI: 1.94-8.31; p < 0.001). FTD patients had approximately twice the expected mortality for age- and sex-matched individuals in the general population (SMR: 1.97; 95% CI: 1.59-2.38), with the highest excess mortality in FTD-ALS patients (SMR: 4.08).

DISCUSSION: This Brazilian hospital-based cohort reveals alarming diagnostic delays despite typical clinical phenotypes and high mortality across all FTD subtypes relative to the general population. These findings highlight the need for improved FTD awareness and specialized training among healthcare providers in Brazil and similar Latin American countries, underscoring the value of hospital-based cohort studies in characterizing FTD in low- and middle-income countries.