TRIM21 and immunodeficiency disease: Since LIP is mostly associated with immunodeficiency diseases, in order to exclude the presence of related primary diseases, rheumatoid immune-related tests were examined: MPO-ANCA: 0.22 mL/L, PR3-ANCA: <0.5 mL/L; rheumatoid factor antibodies: lgM: 0.1 U/mL, lgA: 0.1 U/mL, lgG: 0.1 U/mL; anti-cyclic citrullinated peptide antibody (anti-CCP antibody) < 0.50 U/mL; ENA antibody screening: except for anti-SSA/Ro52 antibody suggesting weak positivity, anti-dsDNA antibody, anti-nuclear chromatin antibody, anti-RNA antibody, anti-Scl-70 antibody and anti-Jo-1 antibody were all negative.