Except for rheumatoid factor (RF) and anti-cyclic peptide containing citrulline (anti-CCP), other auto-antibodies for mixed connective tissue disease were all negative, including anti-nuclear antibody (ANA), anti-neutrophil cytoplasmic antibody (ANCA), anti-SSA, anti-SSB, anti-dsDNA, anti-thyroglobulin, anti-thyroperoxidase, and anti-TSH receptor antibodies. Here, TPO is linked to mixed connective tissue disease.