IQR: interquartile range; SSc: systemic sclerosis, SjS: Sjögren's syndrome; MPA: microscopic polyangiitis; RP: relapsing polychondritis; PCP: Pneumocystis pneumonia; TMP-SMX: trimethoprim-sulfamethoxazole; MTX: methotrexate; TAC: tacrolimus; eGFR: estimated glomerular filtration rate; KL-6: Krebs von den Lungen-6; SP-D: surfactant protein D; PCR: polymerase chain reaction; ST: trimethoprim-sulfamethoxazole; LDH: lactate dehydrogenase; CRP: C-reactive protein; PaO2/FiO2: partial pressure of oxygen/fraction of inspired oxygen; PCR: polymerase chain reaction; PSL: prednisolone. Here, CRP is linked to microscopic polyangiitis.