In case of a negative IIF test, selected specific antibody testing should nevertheless be carried out in the context of strong clinical suspicion on certain diagnoses (for example, anti-Jo-1 in the case of PM/DM, anti-SS-A (Ro60) in case of SjS, congenital heart block or neonatal lupus, anti-ribosomal P protein in the case of SLE) (32–34). Here, TRIM21 is linked to systemic lupus erythematosus.