Rare diseases in Brazil: a nationwide analysis of the diagnostic odyssey

The diagnostic odyssey of individuals with rare diseases is prolonged and associated with clinical, emotional, and financial burden. In Brazil, data on diagnostic delays and their determinants remain scarce.

This study aims to characterize the diagnostic odyssey of individuals with rare diseases using data from the Brazilian Rare Diseases Network (RARAS).

This descriptive cross-sectional study analyzed ambispective data collected from 2018-2025 across RARAS centers nationwide. Diagnostic odyssey was defined as the time between symptom onset and definitive diagnosis. Prenatal and newborn screening diagnoses were excluded. Sociodemographic, clinical and etiological data were collected through a standardized REDCap-based instrument.

Among 18,625 unique participants, 12,048 had confirmed diagnoses and 5,984 met criteria for diagnostic odyssey analysis. The mean diagnostic interval was 6.21 years (± 8.41; median 2.94, IQR 0.80-8.13), indicating substantial heterogeneity. Longer delays were observed in individuals with symptom onset during adolescence. Patients referred during hospital admission experienced shorter diagnostic intervals. Regional differences were significant (p <0.001), with longer intervals in the Southeast region. Mean time to diagnosis ranged from 2.01 (± 2.89) years (achondroplasia) to 16.40 (± 12.59) years (hereditary angioedema). Patients consulted a mean of 5.32 (± 9.63) physicians and accessed 3.15 (± 4.96) healthcare services before diagnosis. Diagnostic intervals varied by race/ethnicity and etiological category, with longer delays among those with molecular diagnoses, while no association was observed with socioeconomic class.

The diagnostic odyssey for rare diseases in Brazil remains prolonged and heterogeneous, reflecting structural disparities, healthcare fragmentation, and diagnostic complexity. These findings suggest that delays are not driven solely by limited access to advanced diagnostics, but also by barriers in early recognition, referral pathways, and care coordination, underscoring the need for integrated strategies across the health system.