HLA-B27 positivity in a large miscegenated population of 5,389,143 healthy blood marrow donors in Brazil

Abstract

Background The prevalence of HLA-B27 gene positivity in healthy Caucasian communities varies between 8 and 14%. However, there is a lack of information in countries with a high rate of miscegenation, such as Brazil.

Aim To estimate the frequency of HLA-B27 in the Brazilian general population using a large national registry database.

Methods This is a cross-sectional ecological study using the Brazilian Registry of Volunteer Bone Marrow Donors (REDOME) database on HLA-B27 allelic frequency and proportion of positives of healthy donors (18–60 years old). Data were analyzed according to sex, age, race (by self-reported skin color recommended by the Brazilian Institute of Geography and Statistics - IBGE), and geographic region of residence.

Results From 1994 to 2022, a total of 5,389,143 healthy bone marrow donors were included. The overall positivity for HLA-B27 was 4.35% (CI 95% 4.32–4.37%), regardless of sex and age (57.2% were women, mean age was 41.7yo). However, there was a difference between races: 4.85% in Whites; 2.92% in Blacks; 3.76% in Pardos (Browns i.e. mixed races); 3.95% in Amarelos (Yellows i.e. Asian Brazilians); and 3.18% in Indigenous. There was also a difference regarding geographic region of residence (North: 3.62%; Northeast: 3.63%; Southeast: 4.29%; Midwest: 4.5% and 5.25% in South). The homozygosity rate for the HLA-B27 was 1.32% of all the positives and only 0.06% in the general population.

Conclusions Our findings provide the first Brazilian national prevalence for HLA-B27 in 4.35%. There is a gradient gene positivity from North to South, suggesting that the genetic background related to the miscegenation due to colonization, slavery, and some later waves of immigration together with internal migratory flows, could explain our findings.