Characterization of antinuclear, myositis-specific, and myositis-associated antibodies in patients with systemic autoimmune myopathies

• Grant number: 25/06363-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2025
• End date: May 31, 2026
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Samuel Katsuyuki Shinjo
• Grantee: Rafaella do Amaral Barbosa
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Idiopathic inflammatory myopathies (IIMs), also known as systemic autoimmune myopathies (SAMs), are a group of rare rheumatic diseases that predominantly affect striated skeletal muscle. However, other organs and systems - such as the skin, heart, lungs, and joints - can also be involved. Similar to other systemic autoimmune rheumatic diseases (SARDs), the detection of autoantibodies has proven useful both for the diagnosis of SAMs and for predicting their phenotypic manifestations, progression, and prognosis. Nevertheless, studies investigating the association between patterns of various myositis-specific and myositis-associated autoantibodies and the presence of antinuclear antibodies (ANA) remain limited. ANA testing, in turn, has been widely used as an initial screening tool for SARDs due to its simplicity, accessibility, and broad availability in public and private laboratories, enabling the early identification of possible SAM cases. Given this context, the main objective of the present study is to assess the frequency of ANA positivity in patients with SAM. Secondarily, it aims to determine the frequency of autoantibody positivity in these patients, correlate these two variables, and identify possible phenotypic manifestations associated with SAM. It is expected that the analysis of ANA patterns will contribute to a better characterization of SAM patients and to the identification of associations between these patterns, myositis-specific and myositis-associated autoantibodies, clinical phenotypes, and their respective diagnoses.