PRTN3 and myositis disease: Her antinuclear antibodies (ANA), extractable nuclear antigen (ENA) antibodies, and extended myositis panel were negative, leaving the underlying cause unclear (ds-DNA: 2 IU/mL (reference range (RR): <10 IU/mL), proteinase 3 antibody: 0.3 IU/mL (RR: <2 IU/mL), myeloperoxidase antibody: 0.1 IU/mL (RR: <5 IU/mL), neutrophil anti-MPO antibodies: <0.2 (RR: <3.5 IU/mL), neutrophil anti-PR3 antibody: <0.2 (RR: <2 IU/mL), and immunoglobulin G4: 0.24 g/L (RR: <1.3 g/L)).