TRIM21 and polymyositis: FEU, Fibrinogen equivalent units; ANA, Antinuclear antibody; Anti dsDNA, Anti double-stranded DNA; Anti RO52, Anti-tripartite motif-containing 21; Anti-SSA, Anti-Sjögren's-syndrome-related antigen A; Anti-Sm, Anti-Smith; Anti-RNP, Anti-ribonucleoprotein; Anti PCNA, Anti-proliferating cell nuclear antigen; Anti-MA-M2, Anti-mitochondrial M2; Anti PM-Scl, Anti-polymyositis/scleroderma; AST, Aspartate aminotransferase; ALT, Alanine aminotransferase; TSH, Thyroid stimulating hormone; FT4, Free thyroxine; INR, International normalized ratio.