de Azevedo Lopes et al. Adv Rheumatol (2021) 61:64 https://doi.org/10.1186/s42358-021-00222-3 RESEARCH Clinical and laboratory characteristics of Brazilian versus non-Brazilian primary antiphospholipid syndrome patients in AntiPhospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking (APS ACTION) clinical database and repository Erivelton de Azevedo Lopes 1 , Gustavo Guimarães Moreira Balbi 1,2 , Maria G. Tektonidou 3 , Vittorio Pengo 4 , Savino Sciascia 5 , Amaia Ugarte 6 , H. Michael Belmont 7 , Maria Gerosa 8 , Paul R. Fortin 9 , Chary Lopez-Pedrera 10 , Lanlan Ji 11 , Hannah Cohen 12 , Guilherme Ramires de Jesús 13 , D. Ware Branch 14 , Cecilia Nalli 15 , Michelle Petri 16 , Esther Rodriguez 17 , Nina Kello 18 , Roberto Ríos-Garcés 19 , Jason S. Knight 20 , Tatsuya Atsumi 21 , Rohan Willis 22 , Maria Laura Bertolaccini 23 , Doruk Erkan 24 and Danieli Andrade 1* on behalf of APS ACTION Abstract Background: Antiphospholipid syndrome (APS) is characterized by episodes of thrombosis, obstetric morbidity or both, associated with persistently positive antiphospholipid antibodies (aPL). Studying the profile of a rare disease in an admixed population is important as it can provide new insights for understanding an autoimmune disease. In this sense of miscegenation, Brazil is characterized by one of the most heterogeneous populations in the world, which is the result of five centuries of interethnic crosses of people from three continents. The objective of this study was to compare the clinical and laboratory characteristics of Brazilian vs. non-Brazilian primary antiphospholipid syndrome (PAPS) patients. Methods: We classified PAPS patients into 2 groups: Brazilian PAPS patients (BPAPS) and PAPS patients from other countries (non-BPAPS). They were compared regarding demographic characteristics, criteria and non-criteria APS manifestations, antiphospholipid antibody (aPL) profile, and the adjusted Global Antiphospholipid Syndrome Score (aGAPSS). Results: We included 415 PAPS patients (88 [21%] BPAPS and 327 [79%] non-BPAPS). Brazilian patients were signifi- cantly younger, more frequently female, sedentary, obese, non-white, and had a higher frequency of livedo (25% vs. 10%, p < 0.001), cognitive dysfunction (21% vs. 8%, p = 0.001) and seizures (16% vs. 7%, p = 0.007), and a lower frequency of thrombocytopenia (9% vs. 18%, p = 0.037). Additionally, they were more frequently positive for lupus © The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Open Access Advances in Rheumatology *Correspondence: danieli.andrade@hc.fm.usp.br 1 University of São Paulo, Av. Dr. Arnaldo 455, Third Floor, Room 3109, São Paulo 01246903, Brazil Full list of author information is available at the end of the article